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_1?HYSICPJJ TESTING C? 30A=Sl ANlD CONTI-INES

P~,DJW TN'2 PrTXTLLON OF' P2SntTS

Prepared for

Tjt- FO1U$Pfl473 1CoAFT INSTITUTE

(Project noB)

lby

TheIntituto of Pnnor chonicotry

Part L t

lPpjctO-jh Wjgconrifif

Jiuno 2, 1945

Copyright, 19 4+5, by

The Institute of Paper ChemistrY

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152

FOLDING ETDURANCE

422. American Instrument Company, Inc. Calibrator for foldingtqsterso (chopper and others). Bulletin 500:3-4(Sept., 1934).

A brief description of the calibrator which is described byCarson and-Snyder in National Bureau Standards, Tech. Paper No. 357.

425. .American Society for Testing Materials. Standard method of test for folding endurance of paper. A.S.T.M. Designation D 643 - 43.A.S.T.M. Standards 1944,-part III:336-340; A.S.T.M. Standards on paperand paper products, Nov., 1943:82-86.

This method corresponds to TAPPI Standard T 423.

424. American Society for Tooting Materials. Paper and paperboard--characteristics, nomenclature, and significance of tests. Philadelphia,The Society, 1944.

Folding Endurance. The folding endurance test has much significance,ranking along with bursting and tearing strength among the physical strength properties most to be desired in many types of papers. Foldingendurance is of particular importance in such papers as box lining, bag,bond, ledger, currency, cover, index, and in numerous other applicationswhere paper is subJected to harsh or repeated folding. The markeddifference in folding endurance with the grain and across the grain isevidence that sheet structure has an important bearing on this quality.However, results are influenced in varying degrees by surface treatment,such as sizing and calendoring. Some types of surface coatings affectthe values, particularly when the coatings arc absorbed into the fibersto the oxtont that they may be stiffened, softened, or otherwise altered.The effect produced by changes of fiber characteristics io illustratedby the fact that the moisture content of the paper has a Lmch morepronounced influence on the folding endurance than on any other ofthu common physical tests. Because of the marked influence of atmos-phuric conditions, it is most important that tests bo conducted inthe prescribed manner under standard relative humidity and. temperatureconditions. Since spocimnon arc folded while under tension, the tensilestrength of the papor may also have come offoct on its folding properties.While folding endurance is an empirical property, it also defines one ofthe elements of utility, as well as of manufacture. The values obtainedare absolute.

42_. .'-thor oasting Instrument Co., Inc. Anthor folding endurancetester. CitLialar .15. v. id.

The spucimIen is heldc andor standard teorcion Ly two Jaws of thefloating typc which movr in the same horizontal plane without rotation.They are k-ept in ouri'cct alignment by frictionleas supports. A recipro-catinc blado doubLeh fulAd the specimen between the quadrant rollers untili-t breaks at the crease. The number of double folds is registered on a4-figure counter. At the -point of rupture the counter is instantly dis-oeraged and the motor stopped.

Folding Endurance 155

426. Bailey; A. J. Fold failure in !craft paper. Paper Ind. 21,no. 2:156-160(May, 1939); B. I. P. C. 9:462; C. A. 33:5182; B. C. P. A.1939B:925.

It appcars that a strong fibor-to-fibor bond and a good shoot for- -nmtiorn provcnting soparation of individual fibers ore highly importantfor obtaining a high folding utrongth. The following factors contributet) higher f olding endurance: Cooking and bleaching procoosco favoringhigh individu'J. f:bor strength and retention of gel-forming materialin th fibc-ro, a beating operation forming this go with a ninirin offiber destruction, a ccmcnting size, nooans of osecuring a random fiberorienrttion in thu shoot, and proper calondcring proccduroo with regardto to:nperature, noicturc and pressure.

427. btuoeUon, M. D. Uniform conditions for' papor testing. PaperTrado J. 92, no. 24:7 8 (Juno 11, 1931); Paper Mill 54, no. 23:18, 50(Juno 6, 1931); Pulp Paper Mag. Canada 31, no. 27:790, 810(July 2, 1931);C. A. 25:5024; T. S. 93:195.

This article is primarily a plea for standard conditions of tempera-turc and humidity. It is pointed out that a sample folded at 65% rcla-tive humidity and 70° F. will show a test averaging approximately doublethat shown by the same shoot conditioned and tested at 50% and if thetemperature be raised to 90 degrees and the relative humidity to 70or 75%, the tear may be tripled or even more. The fold test is themost susceptible to small changes in temperature and relative humiditybut tear oan Millon and other tcets arc affected to an appreciable degree.Tho fact that folding endurance is being recognized as one of the mostsignificant physical tests for hig,,h graCo papers is demanding uniformtesting condltions.

.42c. Bo iding and tonsileo trongth tootor for popeor board, etc.Popior-Febr. 22:65 8-659(0ct. 19, 1924); T. S. 81:70.

The raw Schoppor bending and tensile strength tostor for paper-board in pictured and briefly described.

429. 7c3)dinc tcotor for paper board. Paper Trade J. 82, no. 3:47(Jan. 21, 1260).

An abstract from a pamphlet distributed by Foroign Papor Mills, Inc.,describing the Naumarn-Schoppor bending tester. Examples of practicalapplicato-.i are pointed out. Similar to the article by Naumann inWochbl. FP-iorfabr.

430. Bcrcovitz, D. Apparatus for the measurement of the deflectionor bending of paper under various moisture conditions. Zcllotoff u.Papior 10, ro. 1:C0(Tan., 1930); T. S. 92:4.

Description of Lponrotus and methods.

� ----I· ----�


. _ ... 431. Borndt, Kurt. Latest laboratory instruments for the pulpand paper industry. Zollstoff u. Papier -17, no.- -:09--314; no. 8: 349-352(July, August, 1937); B. I. P. C. 8:74; C. A. 31:8188; B. C. A.

- -- 1957B:1321; T. S. 106:95.

The review includes a discussion of the Schopper endurance bendingtester.

452. Carrier, N. H., and Young,' J. H. An application of statisticalmethods to the dotcrnination of the folding ndurance of paper. World'sPaper Trade Rev. 105, no. 20:159Q3-1594, 1596, 1598, l600, 1602(May 15,1935); B. I. P. C. 13 T. .103:380; B. S. A. 1936B:636.

An analysis is given of the results of folding tests made on severalconsignment of mold-made paper. The methods of analysis arc not givenbut the article is of interest in that it gives examples of the value ofstatistical analysis in drawing deductions as to the significance ofindividual factors influencing the property being measured. From thedata presented, conclusions are drawn concerning the effect upon foldingstrength of such factors as selection of the sample shoots, the particularinstrument employed in making the test, .the direction of the shoot, thehumidity to which the paper was subjected in seasoning and the consign-ment from which the samples were selected.

4_ 5. Carson, F. T., and Snyder, L. W. Calibration and adjustmentof the Schopper folding tester. National Bur. Standards, Tech. Paper No.357. Oct. 15, 1922. [Vol. 2:125-140].

The Schopper folding tester, which is designed to test the bendingendurance of paper and its resistance to such types of wear as involvecreasing and folding, ir so constructed that a number of variables areintroduced by reason of the several rollers and. other working partswhich are dr-iven by the specimen bci:g tested. Those mechanical variablesaffect the folding results in mcc!: the same anner as do errors in ad-justing the tension applied to the specimen during the tost and apparentlycan in general be expressed as equivalent effective tension. The tensionon, the specicnl is very critical, the effect on the folding resultsbeing inversely proportional to something like the tenth power of thetension (according to available data). The variables listed are: fold-ing blade nnl li.n1._ago, quadrantai rollers, supporting rollers, andtonsion on the clnmp sprirs. Under the adjustment of the clamp springthere is a discusnioj: of the; vcrticni susnpcnsion method and calibra-tior in pinc :, inc.ud-ing¥ tlc rric'ion: ess pulley and a now method in-volvi!: a balanced b2:.l-crronk ie.co. annll errors in adjustment are,for th, rt.Cst part, inconuoquential but errors in adjustment amountingto more then about '5 grains i.r t-enion become serious. The frictionin the rollers, particularly in the vertical ar.ndrontol rollers, maybe considerable. Stati,: friction in the quL'cd.rLntl 'iOllors equivalentto 50 to 100 grams tori .o:i cnpcra to be unlvoidablo. A method isOuggostod for =manurii: roller friction.

- I - -- --- -- . -1 -- , - u .- . -.: ; .

I

Folding Enduranco 155

44. Clark, Frederic C. Paper testing methods. New York, TAPPIPublishing Corpn., 1920. 24 p.

Folding endurance is discussed on p. 14-15. The calibration ofthe Schoppor folding-machino is described-. -- - -

~ - 435. Clark, Jamcs d'A. Method and apparatus for testing the-folding endurance of paper and like materials. U. S. patent 2,179,1-16-(Nov. 7, 1959); C. A. 34:1486; Papormaking Abstr. 1941:70.

This covers the Thwing multiple fold tester.

43b. Drying upon the paper machine. Papicr-Ztg. 61, no. 60:1134-1135(July 25, 1936); B. I. P. C. 7:71.

The importance of uniform moisture conditions in testing rooms isstressed. An example is given, in which variations of 1% above or belowthe standard moisture content resulted in variations of 200 or more doublefolds.

4_7. Evans, A. II. M. I. T. folding tester. World's Paper TradeRev. 101, no. 17:1325(April 27, 1934); B. I. P. C. 4:245; T. S. 100:78.

A very brief description, with illustration, of the M. I. T. foldingtester.

48. Fournier, Raymond. Folding resistance of paper. Papeterie55, no. 3:146, 149-150(Feb. 10, 1931); T. S. 92:345; C. A. 25:2286;B. I. P. C. 1, no. 7:14.

A description is given of a new type of folding resistance teeter,based on the same principle as the Schoppor-Rieglor tester but quitodifforcrt in construction. The test strip is 15 by 180 rm. and both endsare climped in a two-kg. weight, so that the tension is exactly one kg.The fold is effected by passing the test strip through a slot in a bladewhich iE reciprocated vertically between 2 pairs of 14-mm. stool rollsmountecid on ball bearings. When the strip breaks, the fall of theweight stops tho motor and applies a powerful brake to the flywheel.An automatic revolution counter indicates the number of double folds.

439. CGreen's improved standard folding tester. Paper Mill 47,no. 13:10, 32, 34(March 31, 1923); T. S. 77:1.

It is pointed out that this tester (developed about 1917) producesan abrupt flexuro in a standard way and imposes the pressure alonG theline of fold and to a fixed and predetcrmined dc 4grec, entirely free fromfriction. The operation of the tester is described. A chart shows therelation of folding endurance and other properties to the tiin of boating.

440. Harrison, V. G. W. Paper testing. XIII. The folding on-durance of paper. Patra J. 2, no. 4:171-174(Jai)., 1939); B. I. P. C.9:312.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Folding Endurance

A description Is given of the Schopper folding endurance testerand of the conditions for carrying out the test eas employed in the7A'TPxmA labo.ratories.

Hau±'y, Fritz. "Paper strength in theory and practice. Wochb3..Papierfaor. 66, no'. 27:512 515; no. 29:54f5-5kSQ(-,ulj 6,-2o, -15535);-…Panlicr-Fobr. 33, no. 28:233-235(Jul~y x4, 1955); C. A. 29:85217;13. r.-_1. c. 6:184;-T.-s..o3:27.

The control methods for paper strength t6sting at the Papyrusplan,,t cf the Waldhof Pulp Mills include tenuile strength (breakinglenEgth), number of folds, and bursting strength. However, only thetwo former are considered in this study, in which the mean values woreobtained~ from the control tooting laboratory's protocols with daotaex~tending,- over a ten-month period. -An attempt was made to measure theef~cctc of varying conditions existing at different stages of the man-uffactu'inG process on the strength of the finished shieet. in preparinghis rgraphn, floury used the arithmetical m6on. (14) of st~rength testscarried out with strips cut inP the machine direction, (1) and in theCrass direction C(9. The strength ratio of l/_j is termed Z, and, wheonI = 1, 1M =a(Z + 1)/a. Two different types of slow 'stock T7o-753 3.--It)aInd three classes of free stock (35-40e S.-R.) were used. Whecn thenumber of' folds were plotted against grams per square meter,,the imaxinfuinstreng:,th lay within the range 55-70'r grams per square meter. Accordingto practical tests, the weight/volume of the finished sheet does riotincrease l~inearly with the ariount of stock that flows on the wire in aCiven time., Here, too, the curves follow a course and show Maximachildler to the folding ecidUrance-weight/voluneo graphs. However, similarrelationships did not obtain between M for breaking leng-th and, gramsper square meter of the finished. sheet. Thec tecring length is a measureof tWhe feltin- of thefie throughout the length of the strip, where~as

th -fodin;s ondiinrance is limited t:- an exceed~iigly narrow area, 'and thusccer%-s 1, record the behavior of tndifividual fibers. in. machnine-made

t~mrthis toot is cspoelolly valualeni in shjowin- the relaction betweenfiber 0r2nato r4 strength. These anti other instainces serve toShow! that the folding enldurance test, is of mriterkd practical -value. Do-termin~nionn of the perczntange moistureo of t~he sheect as it enters the

dlry e~nd of the paper machine strengthens the hypothesniis that shripnkage,irhih is at its maximan with those papers that, retain nest water, ise('vrrlatcd with the folding3 endurance dlata. 'With a moisture contentirecrcasing item 0 to 1~5%, the number of folds incre.-ase and the tearingle~nt-th decreases. The effect of tension during-, manufacture was noted an.O.the results wore supplemecnted by the use of a new laboratory instruL entLye measuring the percentage of stretch in ltest sheets mand® in sheetzanichinUS. Thlis instrument is fully describe. and furnishes a quantita-ti1vu neasure rjf the effects of the deg~ree of boat-iing a d of water coo-tenDt ol the stock on the eloongation of theo slheet under tension,.

44I2. Hodin Ltd. Hodin paper folding tester. Circular, n. d.

One of the two jaws, similar to 'the one desi(gned by 14I. I. T., as-CHilton through an ang;le of' 270 degrees- and is at its center provided

Folding Endurance 115'(

with two edges between which the paper is clamped and. aver v:hich thepaper itt bc-nt altern-atoly. The folding therefore always occurs alont&

- - -- -- non and the same line. The jaw, with the oxcentiork Of' the edges, isriado at' a >6ry 3.iht motal and-when. changing thic-iroction. of folcl~in-!

tespeed Is reduced; the effect of inrertsa, which would introduce stray -Lt!rknowr frTces, A-"s there by uliml~nated. The other jaw holds the paperunder ten-sion whichr ma-y be~ at~justu~4 frofai 0,25 to 1.0 pounds. The jawt3uOn' uot rnevio sco na to cause, the tenuion to fluctuate; of -the points ofcontract a-Ir, Triccinn njar tho fold. are simple, th ere nrjvary littleviear aedJ2t7nt trfe with the r~ccalts. ' ThO usol.1 Sm'e0d is32(0 oIs ~1jxl minut.U"0

lit-K hertCeg,. C. c.,2hte, E. R., and Corpanter, L. A.t11ucsurcma,~,nt of' strnenth. aid stiff'ness of' fiber boards bj recrs ofuta tic' ben6ing. Pa Te'rude J. 89, no. I7:50(-53(0nt. 24, 1929);Tuh) Fiiper Mweg. Unnadan 23, flo. I8:U6)7-(71-(Oct. 3, 1929); Pop'~r14111 52, no. fi4:l0, 12, 55-35(N1ov. 2, 1929,); TI. 8. 91.:91; C. A. 2)4:959.

A rzrthod heni boon. developed for the evaluation of the atrength andrtiallfncss of fiber boards by a static bond.inU test from which the noduliof trnsvsrss strength, rupture, aMd cloaticity ore obtained. Theoovalues- aroc expressed In terms thut evaluated the utrltoturnl. propertiesof the material, and not simply the properties of the piece under -test.'The values can be regarded with little or none af the qualifying datanu'cessary in the empirical methods applied in mills at the presenttine. The method. is otriple and Inexpensive and has been shown to besufficienbly accurate for the pur~pose. It may be applied to boards ofa wideL ;,-aricty and,1 is particularly usefhl in deten'idinin the strength

of roulot-irr- anti, well boards. A further applica-tion is in the testin.-of" nulne, -for stren,7t'h, where it has boon found, to hove a jparticularvolue, In the ev~aluati~on of QrouhiriwDotl r~uin,.

4:04_ iwizbor., W. ½~cperl'iox obtained i'r..r worlhirn wi7th threeSe horppr frldnrs. Mitt. klc~. noeh.-teeh. Verouchs 19, no. 14:161-i83(1903.); Wr~chbl.- Papieirfdbi'. 3-5, no). 14:873-876; no. 16:l003-1C05; no.18:115). 1153; no. 20:l268-3J270 n.29l(3-1; no. 37:240oi-2b108(AprII 5,19, 1aY 3, 17, July 19, SeptA. 13, 1902).

The results of this xtnsv study ore pruesnted in a scrl-C's oDf17 table. !_,L It d!C, not cove-(r paro:Irs of hiCgh. fodn c nduranco. The0wide~ di'foru;ncs obtainn~ ix indiviffun) touts ore duec to nonuniformilty

tf tt r)lar or an rob, to my;-, fault 'if the*, Machines. Ave~rnges of testslnbt ircin for 9' pnape~rs wrhIch hadi fror~i 2 tbe 212; aDzyblo folds

inwica';e tht thu foiling, nusbor incroasocd 126% when the teonsiont wasrfuuo..iY:t 1000 tn 900 -gratis, _-38%~ f-an 1-000 t, 800 (;ran, andc 71h%31

*ro X100 to '(00 r-cj. In, the vi cinit~v ot 1000 ,rami',tht'lignuriber IC affected, approximately i% ."D it each Jt hange in, tension.The folding enduranLce is affected 1.5% far every 0.03 m.changc in

distac between the slotted plate, which creases~- herc paper, nd the;rollers between which, ~thc parper poseses. When, the ro] lets wer atat 0.53 end.r 0.54 rmt. fromn the plate, the averarge_ tc'cnacTcreosuin the folding3 nuriber Ler the creater dist!onc, was 1352%1. Ho ~eoa

nrfta distance of' 0.33 rmzi In a study of t1he~ operatin~ speed~ It

Folding Endurance15

was feoind that the average percentage differences of the folding numbers,using, Ur55 revolutions per miruto. as a basis, were: 45, 99%; 6o, 96%;20, .114%; 100, 105%, 109, 88%,; 130, 96%. He recommends a speed of~

- 100 to 120 revolutions por minute.

41jf'r. UFrzborg, W1. Folding resistance of normal papters. I.Wochbl. Panicrfabr.-415, no. 2l:1854t-1856(Hnay ?3, 1914).

Data ore given for '35 papers.

10s6. Horzbeorc, W. lFurther oxpcrimcrts with the Sohopper tester.Mitt. k-l. m-ch. -tech. Versuchs. 26:1BJ.(1902); Papior-Ztr. 33, no. 56:

* ~~2179-2180(JuLy 12, 19-08); C. A. 3:246.

Variations of results obtained with the Sehopper tester are clueto fruity Ymnipulation anOd lack of uniformity of papers tasted. The.machine, works snirub4y witch vropev handling, cnM the 'results chock

vor : oscly. The following cuercstions are given for obtaining bestresults: keap as free as poseible front d~ust, clean) weekly w,.ith softbrus~h, overhaul thoroug-hly every month, use for papers up to 150 gramsper squcre motor only.

447. Horzborg, W1. Further results with Schopper's folder. Mitt.I4. Mcttorial. 25, no. 1:28-40(1907); Papiocr-Ztg. 32, no. 2 7:118(April 4; 1907);' Wochbl., Papierfabr. 38j, no. 20:1546-1547(MoaY 18, 1907);Papier-Fobr. 5:931(1907); C. A. 1:2490O.

The experience of the Materialprcfungsantr up to Octolber, 1905,* x4Lih the Schopper machine for testiDg the resistance of paper to folding

was ao follows: Complaints reoCrn1dinj -its resul,.ts were faound toteo dueeither to lack of' care of the machine or to nonngoossamples.Tests of different parts of the same papeor argq-eed well. Ton tests on

~seh ofall th clse etdaroci Conpletcly-, and 93% of the controltests prat the paper in the caom class ao the firs,,t tent-. The resultsof S other control tess froy: Octbobr, 1905 to October, 1906, are givenir! tnblos. Of' thece, 93% agreec. with the first ciccsificctior, cni allthe others were just on the border between two classes.

)!43. Ilerzberitg, W. Handc cad, machine folDUing. IMitt. k~l Mnterial.22, Do. 4:200-201(1904); Wo~chbl. ?apicrfabr. 36, no. 14:1006-1007I(Aprll 8,1905); Papierfobr. 3:838(1905).

Hond. foldingr, g,-ives higher results than nnichino tol-aing; a. c., apaper which showed. So double folds by herd. 3ave 37 on the riachine.

Th'clirzberg,, W1. Rcsistminee of )papr tofolding.. M-itt. k,1l.Materiel. 25, Do. 3:1L06-109)(1907); Pcjierx-ZtG. 32, no. 68:2982-2985(Aug,. 25, 1907); W-achbl. Papierfobr. 538, no. 355:2860--28j62(Png.- 31, 1907);0. A. 1:2943..

It has bean. eustonryr, at the U~tran~ug n o make a tesftfor re;s!stan)ce be fo 3i' n 20 st-Ins fr-anr each sampler (if paPer, IC in

- Th,~irz Endvuranco 159

each direction. The results obtained, during 'the past years on 925samples have been examined. comparatively, to See whether testing 5 stripes

- frm) each -directiortn would1 not nyce e ually satisfactory results. Tomake. the cozper2 sOn, 'thd bavcrage of' the first ton toots on each campliewas compared, with that of' the last ton. 'Oat of the 925 papers, of all

-, ~cJaccoon, 794 or 86% wereo-plccod in the same folding class by the f irsttnas by 'the lust ton tests. It is conudd ha to:tssacaf-.

ficiort1 unless the paper gives results very close to the lower limitfor i-tx class, in which case 20 should be token.-

4I~O. florzber-, W1. Resistance to crumpling. Mltt. kgl1. moch.-tbosh. Vorsuchas. 17, no.~ 1:57-60(1899); Papier-Ztg. 24:2463(1899); Wothbl.Pzpiorfabr. 50, no. 491:4503-4504(ncc. 9, 1899).

Tests on stri ps 50 rm., 15 mi. and. 5 mm. wide gave voluos (averagesof machine dnd cross drciootiens ) of 95. 75, 5700 anid 5475 in.; results arealse given for six Samples Using strips 15 and 50 M. wide.

III!. ~dcrzbo-rli, W. Resistance~ to folding in the longitudinal andtansveroe directions of' taper. Mitt. k1l. Material. 33:226-228(193.5);

Pcp~icr--Ztg. IL1, no. 9:137(Jan. 30, 1916); C. A. l0:1268; i4:2262.

Tents of 93.8 papers Showed that the foldin g Strength Is greeterin the Liach-ine direction In about 66%1' of' the papers anid greater in thecross direction, in the rermindur. Variations botween individual speci-mens of a given cloes-of normal tapers ore !rnch greater in the case ofthe fo3.dirg test than. ini the tensile or Stretch tosts.

:)V5L2. Hcrzbe,)rr, W. Vario~tic~n in, the fold-number in trial stripsfreu th snnr, hohet. Mi'tt.k. Mtotrial. 30:1718-180; Wochbl. Papier-f-obr. s; o. 5:4b1V(Sp.21, 1912); PaPier-'Ztg. 37, n~o. 55:1C986)

0vdbar;writ>ng-; nw)ers show a maxiwma variation of over 200% inth, :,nchire n -ctir and. JOOo In. theo cross direction. mch influence *f

Uri-nID'-ro in pape theo ioldirg- number was found to be: 50%P relativehauidit 0- y, fdip- -.unbor of' 50; at 65% 68; at 80%,, 67.

~ How, Luwe. Bndimg Strength tester. U. S. patent 2,151,805

The instrnpsent comprises oirotory disk havin[z a suitable scalesroxtr:t oaportIon :4 ito nor iphory, and.0 a ring- shaped. piece around. the0iisk-, . sultabjon.e prtion, of the ring also being Gradunted. A weighted

L nrpOLUT1at with (a pointer at the top is0 pivoted at the center of theUs!, so as to be r~ntatblo independently of the disk. rhiih lattercnrrier; two nino on;ninst which the test saniple is laid and is held, in-)acc by means o~a third pin connected by a small arm to the pondauliunavrc. flispl1aCOMort Of tlhe disk causes the pendulumi to exert s bendin,7atr~-4 s on thep cardb.Uoard, the r-i-unt, oi bending being measured or) oneof the scntic-,~ and the ztrernGtl' of the ample on the other.

I �, �� --1, . .


b-twoon the anvils under pressure due to the weight of the upper jawassembly. While the lower assembly is on the way up, the specimensare forced into the correct position for creasing by moann of pins (7)

----- which-move alternately to the right and to tho loft, just touching the~puciclnan approximately at the point where the - rease wilrt-e -for-med-.

The pins are operated by a lever actuated. by a earn which is driven bythe sarm -chaft that moves the lower jow-assemibly. By the ti-MI the lowercssr.emly comes into contact with 'the upper assembly, the pins hae-i boonmovedl out of the way. The reciprocating motion of the lower jaw as--sembly is impartedl by moanc of' a moving bar operated by cans at eitherend. An the lower jaws myov avay from the upper jaws, the paper specimensare straightened, and as the supporting bar continues to drop, the entireweight of each lower jawo assembly is supported by the corresponding teststrip. This tension Is maintained until the supporting bar starts itsunvard motion. Ac the bar passes thes zero peint---thint is, that pointin tiW! cycle atu vh~lh t'he speciaens are slways inerte"d- -ali tension isr-eracved,.. As the second cycle bopInsi, thu folding, pins Conec into actionagainl, this tii&: touching! the test strips from the opposite sidec so thatthey fold in the opposite directionr. The pins ore moved out of the way,the; jaws cone togo-thor, api4 -the strip is crecased. This action, is con-tinued until the test'u Specimen breaks. At this point the lower ossomblyIs no longer supported by the specimen as It formerly was durIng oneport of the cycle. Instead, thle lower assembly rides oil the way down. onthe supporting bar, and. the armL which operates the counter for thatparticular specimen or head is disengaged. The instrument was studiedfrom the standpoint of' accuracy of' construction, the effect of' tension,ena the affects resultinCg from the moss of the assembly. An.. approximatelyline~ar relationship existed between -the lo-, of' the folding endurainceaned ttlu, tension for ropers of relatively hig.,h enduraince, whereas forweolcor papers the curves departed from linearity and. develo.ped are-hhl.' charactecristIc- curvature with the co)nvex side toward the origin.Irvrastigeiion indicatedti that the units dlo net act indepkindently and that comn-p.-rable results cannot be obtained unlens the saere nwnber of Heads wereus-cl tit the saout tine. The s~a:rralo havin, 'Ghe poorer formation would, I-ngeneral, give the lower results on thi~s Linstrunelnt, since- the breaking rjf

tbhe: w.-akir strips would~ subject the stronger spocimeons to undue. stress.Certain ouggesctioin arc made for ipvngtheli instruxxn-1t.

h L. Jaco~bsen, P. M4. Hi. Investigation of the folding zmnber.Panicr-Fabr. 25, no. l-7--9; no. 11:178; no. 36:573-574(Jon. -i-, March 15,Sept. 6, 125); T. S. 81:24i5; 82:263.

A nmathematical dizrnvssic~n is g-i-ven of results obtained for thefolding, endurance by unans of the Schoppor apparatus. Twe variablesare considered: (1) uniform te~nsion and different striui widths and (2)variable tens tm)i with co~nstent strip widtth.

t 7-Kicly, Hlolen UI. Bonort on Schoriper tc idim, machine aerThat(I' J. 76, nor 9h5-KMa 0 12) Tech. Aessoc. Papers 6:97-100(Jano, 195); T. S. 77:76.-

Folding TEdurance 162

In, the Schopper' folding machine, it is very important that thespring tension be 1000 grams. By reducing the tension 500 grams, thefold was increased over 1000%.. It is recommended that the rollers be0.015 inch from the folding plate end firmly set in this position.A variation of between 0.015 and 0.013 inch did not show a very wide

-. --.-. - c'd-iscrepancy in results. When the clearance was more than this, great.iscrcpancies were observed. - Dsits are given for five laboratories,from which the following conclusions arc drawn. The relative humidityat which the paper is run is the source of greatest error; a differenceof 5 to 5', in relative humidity shows a marked variation in results.The error caused by paper, machine, and. method of operation is lessin testing the paper cut against the machine direction. It isrocommcntlud. that paper be tested only in the cross direction. A givenmachine checks itself within about 10% as the maximUm except in anoccasional. instance; ally wider variation mast bo attributed to thepaper or motho'd of operation. It appears that the error caused byrelative humidity is more marked between 55 and 70 tlidn between 45and 55'; therefore, it may be advisable to rtnm tests at a lowerhumidity. A tolerance of approximately 30% in the cross directionmust be allowed, in consideration of the results from various labora-tories; therefore, the value of the folding number in purchasing paperon specification is questioned. It does not seem that a minimum valuecan be stated, because there is no ultimate standard machine to whichthe paper can bo referred and a machine will not check itself within10%. If a folding Dumber is to be specified, it is recommended thata tolerance above and below the number determined upon as beingsati-cL.nctory bo allowed. The following tolerances, recommended byF. P. Ve-itch, seem to cover the field:

Number of Folds Tolerances

10-40 1040-100 25

100-200 50200-5n0 100500-1500 250

1500-3000 5003000(- Up 1000

Wor' should be carried out on paper before it is tub sized. Data in-disatc ohat the ongineo-sized paper is sometimes increased as much as1000l by a 4 0 Bd. glue tub size. It in also recommended that work.be-'one on the folding machine after removing one of the plates, whichshould g3ivc a single rather than aQ double fold. Some workl of thiskind indicates that thero is a definite ratio between the single ardo nuble Cold on different types of paper. At present the author foolothat the folding nuibeor nay or may not express the quality of thepaper. However, by running folding tests on the engine-sized paper,the trcat!eont of the raw material con be very carefully supervisedand improperly prepared stock can be corrected.

t

· a�ab·�da�a�lBBb8k�2�e�,. I

Folding Endluranco o

Lj5t. Kiely, Helen U. TAPPI Corrmittee report on folaing; tester.Paper Žrnde J. 75, no. 23:45Z46(bjc. 7, 1922); Parer In&. 4, no. 6:1129, I151(Nov., 1922); T2. S. 75:306.

In a c0o-per tuie stad lyof--the-foldling-teeater, resu~lts-were obtained- -

aim 1 nachinesU. In geIneral the machines were adIjusted by the me thoda? Vc;Itelh, Saxrn.Ejt>' and Roeed and -ails could not be the cause, of the*mr~iatlor in results. 1I1h1an the hur_4dity was not nontrollocl or-voricd-O rinz-g te tuos'L, there wao a noticeable Variation in the tes ts. Wi thbhj, oXp% ;r'f hiumiCity, no reason, could be-, given ror- the, dIscrepancy

rn rsu~c Thec 12 aets of results varied from a I to a 7(2% deviation-1-A th-e avnrage numnbcr of folas. The nunber of fo~lds in the Crass

1~'t~t~nran ~,ory muach more uniform than those in the ianchine direction.On the whole, any given machine seemed to run consistently above ortbcmjrj. the average. Hovever, there wore not sufficient Ldata to drawany :s1el'crel conclusion.

i~.Kienzl, Hubert. Foldinc- iaumber. Papior-Fabr. 25, no.- 38t59S-5197(Sent. 1S, '1927().

46P. Kirchner, Ern-st. BoarO. testinG apparatus. W'ochbl. Pnpior-flh.50, no. 1S:l051-1055(MaY 3, 1.919).

Sun apparatus ic decscribed and illustrated for etetrrtiniG 'themexirmuat' bontlin- atrcng,,th coefficient. flReoults are) given for six typos

]+.Kirchner, Ernst. Tester for bending anti breakinrg juallitiezDIcanburi crn ptn 36298; Papicr-Fabr. 1(:03iA; PuLOp Paper

I-lag. Canada. 109:1308; Papor Trade J. 75,1 no. 26:52.

WCho: cardboard to be tooted is clanpod. in a hinge anid the awlthrough which it may be bent without breakinig, is measurer. and thetonzion. required, for breakiing in reginturod by neann of a spring,,.

!1&2. Kirchncrt s new ttesting apparatus f'or cardboard and0 pape-rWoshbi . Piorfnbr. 50, roo 23:1365-1354(JUnc' 7, 1919).

'5csu~lts ore; u,,Ive-n for t, hoadnada_ boards.

Uc2. KOn, Rt Irm-ectigations, of the now Sihopper boP''ning, cn-Lirnlc Ustter in comparisons with the folcArtng enlu11ronc to-oter. Panio--2

PuLbr. 7'5, no. 5:53-37(Jan. 29, 2.937); Voroi-r ellstOff- u. Papier-Cl'uri~~~~ce1 . ngoPSnicure Jahrcsbericlit 1936:104-10D; lB. I, P,. C. 'T:2-77;

C. A. 51~:4117; 1it C. A. 1957B:332; T. S. 105:372.

The rangeso anrl telativc rzerits of' the ieuw bendling- tester andthe old, told tester arc discussed. Wo simple, coxrrelation between theresultsc of the two inatruments is obtained. For paper, the noaii to-Via~tioris of 50 ifeterninations, the probable errors JrP ite- ovotragos

OnLthe ranges in, th naxi-ritin and ninirun values ware troticolly thuE3Qec Lo~r the new ands the old instrument, rTe errors aC th- nsoa-ure-

itsto crthin cellulosic foils or filnn were greecter for the oild

WnldinS Endurance 3. 64

than. for the newu tester. -The-ratio of folding to bending numbers variesfroim one for writing paper tLo 100 for tissue. Representative date& are-given which show the variations of folding and bending numbers as afunction oI' tension. With few exceptions, the curves of' the logarithmof the bonding niunbers versus tension for different directions for a

- - Ptvon parer and. f or dif ferent basis weiCghts of the same stock extrapolateiincary to a common valu5 of ending, numtor -for- zero tension. -Theson~o cno be oaid'of tho locarithmL. ef the. faihing number versus tensioncurves. It is _- etumosxd that thC eXt6rapolated, bending~ number for zeroUters&non may be irbeornrete)d to a 'material constant-" of the stock. -

4(4. M1-eliitz; Wi11i11am 13. Apparatus for testing sheect material.U. S. patent l,2~ 31,812(Oct. 11, 1932).

An apparatus; designed, particularly for artificial leather, measuresthe force nececcry to produce- a g~iven lateral displacement of thecontrol portion of the campleI and. also the force req~uirod. to rush theopposite edges of a sample toward each other through a given distance.The onppratus consists of a platform, a pair of vertical rails rising;thorefrom, a carries slidable up and. down between, the rails, tho plat-form and carria~o.c having a pair of opposing grooves, one over the other,to receive, the o'PTosito edges) of a place of sheet noatrial to be tested,and an, unstarding- feeler horizontally slidable on the platform towardand from the planes of the grooves.

4:65. Moglitz, William D3. Apparatus for bending sheet material.U. S. poteont l8183Ot 11, 193)

U ~~~~Ain apparatus for tenting- artificial, leather and the like consistsof a base, a standard, a vertical guide supported by the standard abovethe base, a pniunger vertically movable in the guide, tin elongated roll.horizontally supported on the lover Lend of' the plungeor, a platform.to receive weights carried by thle plunger, a work- supporting anvilmounted on the base and adjustable towardl and from the path of thepluriger, means for clompi~ng the work on the anvil with a portion, pro-jecti,,n into the vertical ;Uth Cf the pluncer, and noons for indicatingthe on!-le of bond of the projections portion of the work.

4156. Mloss.-er, H. Pr..orW sing inochines. t roc. Tech. Section,PaT'nr !Makers' Assoc. ('-. Tritcl: Ireland Pi, pamrt 1:77-87(Oct., 1927);

WrdsFa,_Žr Thatto Rev. .2y, r-. 15:1164, 1166, 1168; no. 16:1252,1254t, 12,56; discussion, no:. 17762 36'4-_1365(April 15, 22, 29, 1927);

Papr-Mker75, no. i8-2. LC-9(Mey, 1927); PnPer Makers' Mo- J. 65,

Thr Schorpper folding ese is the recognized standard machine forUeter~mining~ the resistance offered by a paper to repeated. folding;thep n,.,ner of folds is a reliable ~:ieasurc of its cohesive properties.The folding, effect is produced. by a slotted steel plate wThich, by itsreciprocating nor'tion, folds a (tensib~joned) o Lrip of peapor backwards and

Pofrward~s until it breaks. The arced of this machine should be 120 r-p-n.Tuvarious itonor inv.ro1ved. in the calibration ore listed. It is a veryCCDE~iive:-paratus and. demrands iore atten~tion to maintain. than any other

I


tester. 'he head piece and the tension springs are the most importantparts. If the rollers or the slotted plate get out of alignment, the

....-- otest strip is subjected alternately to oblique stresses and will breaktoo early. aIck of lubrication-on-the roller bearings will causeuneven wear in the bearing pin holes; under this condition, the resultsare excessively-high.- - .

467. Mu'rzinger, Walter M. Determining the-bending strength ofartificial leather. Nitrocellulose 5, no. 10:179-181(Oct., 1934);B. I. P. C. 5:88; C. A. 29:1533.

An illustrated description of a motor-driven apparatus.

438. Multiple folding endurance tester (Thwing). Instruments9, no. 3:59(March, 1936).

''en folding tests can bo made simultaneously in this new iO-spindleLdeviL'c. Specimens (15 cm. wide) are held in cam-action locking grips

aiJd cr alternately folded under compression and straightened out undertonrzoln. A definite sharp fold is made under the compression load.Tho compression load is 0.5 1i. Depending upon the grade of paper thetuonrioi lead may b; varied from 0.5 to 3 kg. A tripper folding devicealternately folds the'papcr in two directions. A counter registers

' tnthe numltbr of folds made to the breaking point. If doeired, toots canbc made on fdver thor ton spindles. A clutch is provided to disengage

i: tthe driving mechanism while test pieces are being inserted in gripc.

. ko465a~. Naoumof, K. 'Dtermination of the resistance of paper tocrumpling by the Schopper folder. Papier-Ztg. 30, no. 78:2954-2958;no. C0:3030(Sopt. 28, Oct. 5, 1905).

4l.0. Neaoumof, P. Use of logarithmic coordinatos in paper testing.iletlod of plotting results from Schoppor folding machine. Papior-Ztg.30, no. 74:2802(Sopt. 14, 1905); J. Soc. Chen. Inrl. 24:1028.

n cxpressing the results obtained for the rcsistanco of papertc 'oliLing, by means of the Schoppor folding machine, the tensions'botwocn the springs holding the paper are plotted as abscissas, andthe number of double folds which the paper resists is plotted on theordinate axis. Tie resulting curves have the form of hyperbolas.

!r' TnThoso may be reduced to straight lines by plotting the numbers propor-tionallyr to their logarithms, which may be done on paper ruled forthat purpose. The inclinations of the straight lines so obtained.inidicatc the law according to which the resistance of the particularpaper varies with the tension, whereas any point outside the main lineray be rccoinizecd as an experimental error and corrected as such.

1471. National Association of Purchasing agent, Inc. Corrugatedfibrobaordi chilppi'e containers. No. 19, 1934. - p.

.ondinE Tcst. 'ho official technical test for bcndirf---four snmplos.1 s.mch, inh t.h; wroain running 'oh long way and the short way, shall 1^


carefully cut from the liner cir container to be tested. The samplesshall be 15 mm. (0.59 inch) wide and, of sufficient length to i nsurea firm smnooth grii in the jaws of the tester, and shall be cut fromunwrinkled, unscored, and urbTernished. stock. The teat sample shall

-bthe chmncpd in--the tester (H1. -I. T-.) without-mo .certra. I~ortion (towib~listand. the bendingl) boing touched by the hands, thle tension adjusted

te kuozrnand the spre-imen folded through a combined angle of270 dc;raeo luitilI it breaks. Each of thfe two) sate. ½f four samples ---

(ts' be folde-d with and tpentthe grain, respectively) 'shall be slut-Jlariy tested enid 'the average number-~ of fields each way shell1 determinec')uiipliarce with the npocificotio-o. Not more than one of eoac of thesets of four tests may fall short of' the required. number. However, if'either or both of the two sets of tests in below the soecification, aseries o)f 12 re-tests of that test or -tests, shall, be tan'do:, of whichn-et more than three nay fail to comply, with the avernage of all 12meeting~ the specification, for acceptance. A simple substitute test,ind~icative in a crude, but reansonably re-liable way of bending qualitiesto be desired, coit be nvdo by hand- Linnipulotien of' sonplo boxes andsections of double-faced board cut from- then. The flaps of 'the boxshall' be doubled comipletely back upon the sides, first inwardly and

enenoutardl, u.on the horizontal scores, each bend boing tightlyprronscd down by the hand. This bending shall be repeated until a total*-jf 'three bends have been mjde inwardly and three outwardly, and theaboard inspected both 'inside aind outside, f'or cracking or failure of'the board. Further, twom pieces, appro:ximately 5 inches square, shall

be cut frome an unscored. and. unprinted. section of a boxy and. each shallbe hand scoredl by moons of a ruler or other fairly sharp straight-edge,to break down thle corrugations but not brook or cut the ourfhce of

tmc facingE. Two scores shall be rodeo at right angles to each otherbisecting the board with and against the gri.OenCpcsalb

folded naganst thoe grain or with the cornigations (the~ (rain runo atright angles to the corrug~ations), that. doubled back upon itself' withthe grnin, and. rhall, choir no sirgn of failure when thle second fold is

* ressed down tightly by thes hand. The other narie~l shall be foldedwith the grain, then) doubledl back, upon itself ngainst the Groin, andshall show only slight tearingP at the cor:'or represenrting the junctionIf' the two folds whean nrrssed do-wn tig-,htly by the hand. The interpreta-tion or' the bcn~izig qualities )f' the boar,'. from this last test isn1-osstLriiy at better a- xnoxmŽC-ienco in nnkcinr; the toot anJ shiould beccrsinudered as erecrly irndiecti~ve rf [general. strengIth or weakneMss.

W72. Na-tional Ri~ronu -:f' St~ariferri. Caor end adjustment of' fold<in"teuters of, the Suhn)ppjr typo~. Circular e.379. Nov. 19, 1~929 7 P-

This is a surpleit-otary rernoz't to the nturly of' Carson and Snyder[IDe 433], which (Liscuseed. -the relation of' niozn if thle mechanical-Tariables to 'the., teat results in1 the liGht -of danta then available anddescribed a newly developed delvice, for fadjuetir<- thle, tenion on thesnOcincll. This device., which isq a i:)cd-wcAight, tester iolngtheuse of a balanced boil-crank lever, has been il-pr~oved an d odnted to

the noasurement of' the friction of the. r-llers; th1in iietiiod is described

in detail. 'The, rol-ler frictioni hoe, bonobservoe to %vry from 25 to220 g-rayas equivalent torsiorn anmi usuaIWLLy . from1 50 tuo 30 g-rams for

I1


rollers in good condition. A variation from 25 to 100 Crams is objec-tionmabie but i's about the boot that can be done, considering theItiltat'inon of the tester. A test is doocribed. for detecting poora_ jrflfnpnon of the rollers. A number of' sueggetions are g7iven conrcerninu

hocare and. ndjustnont- of the foling tester.; a procedure is outlined.rrperiodic inornoction. this is essential for the bent results.

L7% National Bureau jf Smndlaidb. -The testing of paper.--Oircu- -

lor L'on. 107. Feb. 1-2, 1921.

A brief description of folding endurance is given on p. 17-18.

V3~, NumanH. Board testing. Zdls~toff u. Panier 5, no. 11:4371 9l~v.,192);T. 8. 82:301.

The construction and application of the Naunonn-Schopper paperboard bendingtester arc Iescribed. Constructional skeotches of therneilinc are Given.

£7_25 ?Naunaun, M. A rbw apparatus for testinCg the bending, strenGthanik', hf bondingr anlet of- board, etc. Wechibl. Phpierfabr. 55, no. 33;20753Cb20s' ncr-. 35:2202-2205; no. 36:2263-2268(Akig. 16, 30, Sept. 6, 1924B;T2. S. C0:247.

The ncw 1:bursnnn-Schopper bending tester for heavy poperso, cardboard,ctc., is describedt at considerable length. The results of actual testsOre re'onroducod in order to demonstrate what may be expected o:f the in-isu L-urn.nt. The followInC advantagesa are claimed for the tester: constantcrn~tol -ff product; influence of thickness and pressuro Onr the bendinCpronortics cnn be ascertained; manufacturing variables can be studied.;the.r arSle of b!reak Is easily deternincd; and the uniformity of the ca-rO,-bo~ard. nay bea Thllnwed.. The abvov hac beer translated. into Er.glish Ond.-oul-iobcc ns Booklet No. 507 of' Louis Schopper.

£7.Naumann. 14. Schopper bending tester. Poapir 29, no. 8:985-QK'(Sept., 126); T. S. 84:278.

A, toot ijeco 50 mm. wide is held In jaws, the inner woile ofurP>cK cor at an) an.-le of 180 degrees. By turnirvg a hand.0 whool the

A t I':ja is Civer a rotary motion, and. the upper Jaw, hinch corrneaa wcighL pordulun, offers a resistance cgqual to the banendin strength

1~ iV of the test piece. It therefore only partially follows the 0.isplace-non~t of' the lower jawr and the angle between the two prad~ually rleerconocs

-% Th~Fie test is continued until t~he test piece brooks, and the scalereaftinG Cives the bendinCg resistance in. kios and. the bending; anglein degrees, the latter being the rnaxinan- angle to) which the productcon be bent. The curve betireen the resistone andL the bending angle1io automatically recorded.. This is covered by U. S. patent 1, 559,4I66

(Ot27, 1(925).

)I 77. Tiew folding,, endurancb tester (Anthor Testingr, InztrrncntCoryo.nny). Panor tfAdel J. 101, no. 2:27(JulY 11, 1935).


4738. Paper Makers' Association of Great Britain & Ireland. Techni-cal Section, Paper Testing Committee. First report. London, The Associa-tion, 1937. 85 p. Also issued, with discussion, as Vol. 18, part 1A,of the Proceedings of the Technical Section. See also World's Paper

- Trade-Rev., Tech. Convention-No., -March, 1957:4-72; B. I. P. C. 7:348.

- Specifications are given for the folding tost using the Schopporfolding tester. The test specimen is 15 + 0.25 =m. in width and 70-nm.in length; the apparatus is driven at such a speed that 90-120 doublefolds per minute are offectod. The test gives information about certainproperties of paper, such as the durability, which cannot be obtainedby other instruments. In the Schoppor tastor, a test strip of theopaperis hold by two clamps attached to helical springs, and the folding iscarried out by the reciprocating action of a vertical blade. The tensionof the springs on the paper is such that, when the paper is extended toits full length, each spring exerts a pull of 770 grums; when the foldingblade is at the limit of its travel, however, and the paper is bent to themaximum, the pull exerted by each of the springs is 1000 grams. Dioad-vantages of the folding test are that strong papers (those that resistupwards of 1000 double-folds) require a long time for the completion ofthe toot and the results on a narrow strip nay show such variations as tocast doubt on the accuracy of the -figures. There arc inherent difficul-

:' ties in. the nature of thu test. Thus, a thin paper has less stress uponj; the fibers of the outer arc of the fold and loss crush upon the fibers of

the inner arc, than is oxerted in the case of a thicker paper. Thefolding test is particularly susceptible to atmospheric influencec.

. Li It is impossible to correct the folding test oven approximately forvariation in substance. Therc is no definite ratio between the width of

i, * the strip and the folding figure and it is necessary to standardize onone width. Sompl.es of a paper ]4, 15, and 16 mm. .vidc gave values of245, 301, and 366 double folds. A lodger paper tasouted at 55, 64, and 7250relative hun.idity, gavo values of 675, 997, and 1587 folds, respectively.Details are -ivcni of the calibration of the spring.

,!!** tS7. Rood, E. 0. Efi'cct of tomnpraturo and rclativo humidity on

tho folding endurance of' paper. Paper Traieo J. 79, no. 25:55-57(Doc. 18,1924); Paper 35, no. 7:209-272(Dcc. 4, 1924); Papor Makcrs' Mo. J. 63, no..1-:17, 29; no. 2:50-52(Jan., Fob., 1925); World's Paper Trade Rev. 83, no.

J 4:290(Jan. 23, 1925); T. S. 31:70.

Tests were made at 60°, 70°, and g5° F. at a relative humidity of65'yj. A rise in temperature causes a decrease in folding endurance,

4| the effect being more marked with tests made in the machine directionthan thoso made in the across machine direction. Theo results show the

.f need of controlling the temperature within limits of approximately 10° F.The effect of the relative humidity was studied by making tests at 25,30, 40, 45, 55, and 65% at a temporaturc of 70° F. (oxccpt 65%, whichmws at 65° P). The results show very markcrC incroascs in the folding

endurance in the rmachi:ne direction as the humidity incrcasccs. Thereis a much loss but more uniform increase in foldin endurance in theacross direction with the inurcsaing relative humidity. The increasein results in the machine direction is very mnrkcd, being from 155 to

I

4_ -r I -.. 1-:1


1409% at 65 rather than at 25% relative humidity; the results in thb cross-direction arc 17 to 299% through the same range. The increase between45 and 65% varied from 40 to 2553 in the machine and 0 to 104% in theacross machine direction. Interesting results owre obtained for different

..typcs of papers. Thus, in changing from 45 to 65% relative humidity,the rosulfts i'o thd-nachine direction showed-incroases_of 276% for kraft,354'; for rope, and 749%o for unbleached sulfitc; in the across machine-direction, 0G% for rope, 135% for kraft, and 330% for unbleached sulfitc.Tub-sized bend and lodgers showed considoroble increase in the machine direction but dififrent samppljs do not show the saBm percentage increase.These results indicate that it is impossible to secure any factor forcnJca.lotins folding endurance results at one condition to equivalents atanother or to a standard condition. Because of the wide difference intlho effect of atmospheric conditions on folding endurance, the comparativetent values of papers cannot be the sane at different humiditics andtcnpcraturso. Therefore, it is paramount that, in the selection andadoption of a standard testing condition, this condition must be inharmony with the use and service demanded of the paper. mT folding cn-duranc in the machine direction of all papers tested is higher at 65%relative humidity than that of the across machine direction. The differencebetween the folding endurance results in the machine and the across nachinodirections is ruch greater with all papers at 700 F. and 65% relativehumidity than it is at 70 ° F. and 45 to 50% relative humidity. The foldingendurance results in the across machine direction at 70 ° F. and 45 to 50%relative humidity are greater with some. papers than those in the nachinedirection. The advantages of using 50% relative humidity for testingarc pointed out.

480. Red, E. 0., and Larson, Frank E. A. Foldiug endurance testvalue. Pulp Paper Mag. Canada 25, no. 4:97(Jan. 22, 1925); C. A. 19:1948;T. S. *1:70.

In connection with work being carried out by the Bureau of Standardsfor the United Typothotao of America, tests have been nado on 94 connorcialbond papers and 59 ledger papers. From the results it appears that thefolding endurance results arc the most indicative of serviceability,durability, and quality, and show the most striking variation in the paperstoctci. Therefore, the folding endurance test, properly i-tcrpretcd andin combination with the bursting or tonsile strength, nay be found suff'i-clct to classify thcse papers.

Z;,

1.o''t

t

481. nibioro-Raverlat, J. Results with the Nauiann-Schopper flexo-molbet as compared with those with the Mullen tester. Ponior 35, no. 10:1055-ln05(Oct., 1932); T. S. 97:72; C. A. 27:1750; B. I. P. C. 3:144.'

From a comparison of the results obtained on tWo different boards,Ut is concluded that there ic a relationship between the results obtuinedwith the two instruments but -that its determination would require furthertests on a more extended range of samples. Though the .ulion testerdoes not permit distinguishing between machine and cross directions,it gives a good discrimination between the two sides of the test piece,ard for a given set of sanplcs, it gives characteristic results whichare in all points comparable with those of the bending testcr. Itprosunts the same drawback of slippage between the jaws, but it is muchsimpler and quicker to operate.

I I

. . in,, ^n--p -. , piirI ii_

I

Folding Enduronco 170

4C2. Ribiere-Raverlat, J. Use of the Naumann-Schopper flexometcrin board manufacture. Papier 35, no. 2:177-178, 181-182, 185-186,189-10,, 193-194, 197-198(Feb., 1932); T. S. 95:75.

Irom a detailed analysis of the mechanism of-the action of the.Naumann-Schoppor flexomotcr and of the information which it gives,

- illustrated-by means of an example of the results obtained with agiven sample and of the curves which can be calculated 'and plotted from thom, the author concludes that the instrument permits of distinguishingbetween the two faces of a sample of board and of revealing tho internaldefects which may exist in the shoot. The operation of obtaining theresults and information, however, is long and tedious and they shouldbe coordinated with a view to subsequent comparisons.

LF83. Schnablo, George L., and Abbott, Frank F. Method of andapparatus for testing fibrous materials. U. S. patent l1,436,323(Nov. 21,1922); C. A. 17:635; Pulp Paper Mag. Canada 22:657.

Paper is subjected to friction by drawing it over stationary platesand simultaneously subjected to repeated folding until separation ofthe matcrisl occurs.

i; ' io4(:. Schoppor, Alfrod. Apparatus for testing the bonding strength: of p)asteboord, cardboard, etc. U. S. patent 1.559,466(Oct. 27, 1925);.g T. S. *3:204.

The test piece io attached to two plates, which are rotatable abouta common. axis, so that, by moving thom in an angular relation with each

[ir ~ other, the test piece is bent end broken. The rotation of one of the(i' plates from a position of rest is opposed by a progroesivoly incrcosing

force produced by a weighted pendulum or equivalent device; moans arcprovided for measuring the anglo through which each plato is moved.

4C5. Schoppor, Alfred. Endurance tentin3 of paper, carton, andboard. Wochbl. Papierfobr. 68, no. 6:97-100; no. 7:119-124(Fob. 6, 15,1937); World's Paper Trade Rev. 109, no. 14:Toch. Supply. :45-60(April 8,.195(); B. I. P. C. 7:277; C. A. 31:4116; T. S. 105:372.

R feronceo is mado to a now type of folding endurance tester, suitablefor tooting paper and board, called the endurance foldirg t-stor. Aosaplc strip 15 nm. wide is bent under constant tension until failureoccurs. The upper sample holder bends the paper through 90 dogrcoo tothe left and to the right of the equilibrium position. The lower clampapplies tension to the strip by means of adjustable weight. The radiiof curvature of the edges of the upper claop are 0.01 mn. The instrumentoperates at a speed of 110 bonds por- minute. Physico-rnthorLmtical con-aiderations and a large number of tabulad ted st data and Craphs arc given.

486. Scribner, B. W., a:)d Snyder, L. W. Stury of physical Droportionof binders board. Paper Trade J. 95, no. 1:29-33(0ct. 20, 1932); C. A.27:1752; T. S. 96:135

.L,

_________

.- -_ . *Folding Endurance 171

Th_ Naumnnn-Sohoppor bonding tester was used. The test specimenswore 2 x `c irches. The inner faces of the two clamp Jaws arc in thesarn:e lance with funds touching when the instrument is in zero position.The outbi surfaces arc-adjustable to-pornit the insertion. of boards ofdifferent thicknesocs. The board is bent by turning a hand wheel, which

--* - causes'.one of the clarps to revolve about a center. The resistance ofthe board to the applied stress causes the "other clamp, which is fastened' -.to a weighted pcnduliun, to revolve about the same counter. The totalmovoinnt of tho second clamp is dependent upon the resistance the boardoffers to the Increasing load applied through the movement of the firstclrap. WVhon the board is broken, a raxiran indicating pointer, whichfollows the novomeont of the second clamp, indicates the bonding strengthon a scale. Data arc given for five samples of boards. The resultsaro ccrlpared with flexural strcrngth tests carried out on a modifiedtonsile strength tester. In general the Naunann-Schopper tests are

'. higher because of the use of a wider tooest specinon and a shorter testspan. Flexural strength tects arc commonly made by supporting the testspecimen on two separated parallel knife dges and applying a load totho specimen at rnidspan. through a third knife edge parallel to the dthertwo. In testing board, however, rods have boon found noro satisfactorythan knife oedes, the rods used for binder boards being 1/8 inch in

-'~ dianctcr. 'The rods wcrc used in the form of stirrups clamped in a stan-dard type of paper tensile breaking strength tester. The details of

,. the stirrup device are shown.. The size of the specimen was 1 x 5 inches.c2 Data ore given for the breaking load and the deflection at rupture for

the lergt!hwius and crosswise directions. In addition the bursting strength~ cand the tensile properties are given.

. LQ487. Sirnords, F. A., and Doughty, B. H. Application of elementarystatistical nctlhols in the testing o01' pulp and paper. Paper Trade J. 97,no. 2;:32-35(Duc. 21, 1935); correction, 98, no. 13:34(March 29, 1934);' Tch. Assoc. Papers 17, -7. l:473-478(June, 1934); B. C. A. 1934B:139;C. A. 2c:2527; T. S. ,.:9.. B. I. P. C. 4:117.

Thc rccults ' ' f'-.llin' endurance tests nmade on several tarn.arack kraftg -i.pr c' -G cI'" .. >f r, i_ n rcanl. eight and. in degree of calendering arc given.

~$ Thn cofi Icl .... .' -reariation var;- over a relatively snall range withoutS any regular trend. 'ljs su-,;cets that, for this particular series at

. uas., the varicblity of the folding test is not influenced either bythe reoan weight, the degree of calendering of the paper, or by thedirection of the tost strip and that the factor of greatest influenceis tho formation of the sheet. Thc values of the probable error ofthe mcan permits certain conclusions as to the significance of the varin-ttims observed in the several runs. It is also possible to calculatetho nuLber ,' -, tests roquircd. to produce an average, the raxirmn error'ft' which will fall within a prcdotcrrnined limit.

48C. Snydler, L. W., and Carson, F. T. A study of th_ M. I. T. paper* :lding tcstcr. Paper Th'adc J. 96, no. 22:40-44(Juno 1, 1933); Zcllctoff'1. PaDier 13, no. 9:441(Sopt., 1933); C. A. 27:40'75; T. S. 98:14; B. I. P. J.3:270.

-- --. . .... Folding Endurance 172

In the M. I. T. folding tester, a strip of paper is fastened atone end in a tension clamp, which is actuated by a spring. The otherend of the strip is fastened in an oscillating clamp, the jaws of which

- terminate -in rounded edges. near the center of oscillation. This clamposcillates through an angle of 135 degrees each way~from the -verticlio- -.--

and in so doing bends the paper, first one way and then the other, aroundthe curved edg6esof-the Jaws.- The tension on the specimen is determinedby the displacement of the tension clamp at the time the strip is fastenedin the two clamps. Some of the features of this design are: No align-meont rollers arc required and there are few working parts which areOriven by the specimen. Tho tension is practically constant throughoutthe folding cycle. The tension may be adjusted easily to any desiredvalue within the capacity of the spring, thus permitting reasonablyrapid testing o. a wide range of papors. Manipulation of the plungerunder lead so as to allow it to come to rest first on the downwardstroke and then. on the upward stroke indicated that the possible errorin applying a given tension to the specimen is of the order of about25 grams, which is in conformity with results of the determination. ofthe average frictional resistance for a tension of 0.5, 1.0, and. 1.5 kg.In addition to this friction in the plunger bearing, another source ofuncertainty in the applied tension results from small vertical displace-morts oi' the specimen itself, necessitated by the fact that a small;portion of the specimen must be wrapped around the odges of the jawsof the oscillating clamp. The choice of a folding clamp such that the

~'. speocimoen to be tested nearly fills in -the distance separating Jaws willj. rn~minimiz2 the tension changes. Tloi change in effective tension resultingff from the curvature and position. of the folding odges is in most cases

small. An. error of 50 grams in the tension applied to the specinon mightresult in an error of 15 to 20% in tho folding results, depending upon.the absolute value of the tension; actually, this is probably high.The curvature of the folding surfaces in discussed but, because of thedifficulty in obtaining, data on this question, it was not studied.Variation: in the folding rate between 130 and 200 double folds per'. .inuto did not appear to affect the results appreciably. Data obtained

b with si. M. I. sT. testers showed that if the folding surfaces werea lways un.do of the correct contour, if tho variation. in. applied tensionwore rlinimizod, and if a sufficiently largo number of tests woro madeand averaged, the tester would yield consicte:nt results. There is nosemblance of correlation. botweon the results obtained with the M. I. T.and the Schoppor tostcrs. The M. I. T. results are always lower,probably because the tension in. tho case of the M. I. T. tester isnearly constant at 1 kg., whu-roas the tension in the case of the SchopportOtoer varies from i to about 0.3 kg. during the folding cycle and because,in the former case, tho sample i: boing continuously bentt. whereas in-th latter It is bont only whilc it is bcins pushed between the foldingrollers oan while it is under tension of about O.c kg. It is evidentthat the specimen is not treated in. the some way ir the two types oftoestre. A proposed method is given for making, 1'. I. T. folding tests.

4h9. TAPPI. Folding endurance of paper. TAPPI Standard T 423 n-41.Approved Standerd--Sopt., 1927; corrccted--Sopt., 1936; reviscd--rFb.1941. 2 shoots. Various versions have appeared in Paper Trade J. 85,

.1* no. 19:60-6l(Nov. 10, 1927); 86, no. 8:211, 213('0ob. 23, 1928); 111, no. 7'34-36(Aug. 15, 1940).


.- _ -- The standard covers the Schopper folding endurance for papers hav-in. a th:!cknoss of not more than 0.01- inch and the M-.- I.- T. folding..enditranco which can be adjusted for papers of any thickness. There is' no constoat relation- between the test values obtained with the twotypes of testers.

4ii0. TAPPI. Operating factors affecting folding endurance.Special Report No. 214. Juno 21, 1934. 14 p. Mimeographed.

Replies arc given from a number of nills regarding the influenceof such factors as cookinti cooking oki temperature, bleaching, beat-ing, sizing, fillers, jordaning, drying, machine speed, etc., on thefolding endurance of paper.

i491. TAPPT. Committoo on Papor To ntig. Folding endurance. Inl ~ Paper testing methods, 12:58-64.

:j,! A cneral dicvres ion is given of the method of using the Schopper.^. ffolding taster (-Lhis Ois ow covered by TAPPI Standard 423 m). A brief

discussion is given of the M. I. T. folding tester.

4. 2 TAPPI. CPoamitte, on wapsr Tcstinf;. Paper testing methods.;. Folding endurance. Paper Trade J. 75, no. 4::43-44(July 27, 1922).

~i ~ The Schopper tester is used; the calibration and accuracy are dis-*- ~cusscd. Mlon.ion is made also of the Green folding tester, designed for

use with hand shots; it is applicable to any shoot irrespective of bulkor tcncile strength. A brief description is given of this tester.

p - i4r4.3- Taylor, Casper E.. Paper-testing machine. U. S. potent1,'i,549(iMarch 6, 1928); T. S. 90:31.

iV' ~ To ensure that the clamps holding the ends of tho test strip shallmve in a true horizontal plano without any lateral yielding or oscilla-tion bout a horizontal axis, horizontal rollers of substantial widthare iprovxidod on which the clamps are made to rest. Vertical adjustingncans for the supporting rollers are provided.

494. Tinius Olsen Testing Machine Co. M. I. T. folding endurancepacper tester. Circular. n. d.

Tn this machine strips of paper 1.5 cm. wide are held between twojaws, the lower of which rotates through a given angle and the paper isthus folded forward and backward around a certain radius. Tle upper headis attached to a weighing system so that a definite tensile load may beapplied to the sample during the foldinG operation.

9 9 .. Veitch, F. P., Saumnct, i'anh, and Peed, E. 0. Folding endurance')f paper. Paper 20, P.o. 12:13-19(May 30, 1917); C. A. 11:2275.

"y;~~~~~~~~~~~~. - :lf'· C~~~~~~~~~~_f ~"'r'~

...... ~ ~-fi-~a -:,. ~I._ .- . .-.

Folding Endursinco 174

- c-Schopbor folding endurancetester (German patent 94,901) hasproviou.ly been studied only by Herzberg. This test is designed to imitate, in a general way, the practical conditions involved in the handling,foldit7, ond' brnmpling-of paper. The numerical exprcssion--the. number of double folds resisted--is an indication of the quality and, probably,of the durability of the paper. Six machines were used in this study;they were standardized with the rollers set at 0.015 inch (Horzborgused 0.015 inch); results obtaircd with machines in which the rollerswere set at 0.015, 0.017, and 0.019 inch were closely concordant. Ami-thod. of sBondardizing the machine is given. Foldirg tests should bemadc-i at approximately 120 revolutions or double folds per minute. Thetost samples wore conditioned at 65 ° and 65% relative humidity. Bond,book, andc lodger papers were examined. The averages of ten tests onthe same or on different machines, using a paper of low or high foldingendurance, are not widely different, when the machines have been care-fully nd.justcd and the tests made under uniform temperature and humidityconditions. A closer agreement is obtained by making 20 tests. The greatirregularity in paper is shown by the maximum and minimum results ob-tainJd or each paper with each machine; 21 to 42' of the individualresults vary loss than 10% from the true mean; 47 to 735 vary less than20-;, and 69 to 89% vary less than 30%. At this time, 16.1% may be rc-gar!. Cd as the maxirnu allowable variation from the moan of averages oftwo cericn of 10 tests on. the sam machine. The data indicate that thedilcoi'-nco between individual results is causedby variations in the paperand not to irregularities in the machine. In routine testing, the foldingcndurcncc is determined only in the weaker direction, which is usuallythe cross machine direction. The avcragc of five tests will generallyindicate the range of folding endurance of a paper, but for closer androro reliable averages, it is advisable to make 10 or even 20 tosts. Theve-races of two sets of 10 tests should not vary more than l6 and those

of 20 tests not more than 11' from their mean. Distinct differences inquality nay be observed in papers, the folding endurance numbers ofwhich differ by 10 when the folding endurance is from 10 to 40 folds, by25 between 40 and 100, by 50 betwcon 100 and 200, and by 100 between 200andl 500. It is believed that the instrument is valuable for indicatingthc probable durability of paper and its suitability for specific purposes.

:--

175

HYGROEXPAMSIVITY

40.6. Abel, J. G. The interpretation of'tdsts-)n paper; Proc.- --- -Tcch. Section, Paper Makers' Assoc. CG. lritain Ireland 14, part 1:171-18'.; iiscusSion, -18 1-- 0(Oct., 1933-); World's. Paper Trade Rev.99, o. 12:867-868, , -870, 90- 913-914, 916(March 24, 1933); Paper-iMa3or 86, no. 2:TS157-l60; no. 3:TS167(ug., Spt., S . 9335) Zellstoffu. Papier 15, no. 5:216 -217(loay, 1933); C. A. 27:5973.; T. S. 98:147.

The Schoppnr wet-stretch tester is an admirable instrument. Byfixing a time'limit of 5 minutes far a test, very reliable comparativetests have been obtained. Papers giving a big stretch under the con-ditions of the test gave a greater expansion in a humid atmospherethan those which gave a low stretch. One strong objection to thetest is the tension which is applied; however, it is difficult tosuggest a remedy.

4±31. Bercovitz, D. Extension meter for testing papers UnderdifJ;'Crent humidity conditions. Zollstoff u. Papior 10, no. 1:40(Jan., 1930); T. S: 92:4.

2; An apparatus is described by which it is possible to measure theextension of ten strips at one time. The samples are placed in the

i apparatus and dry air is passed through until the samples are completelydry. After the length has been measured by means of a micrometer,rmoist air of the desired humidity is passed through (time not stated)and the length again measured. A microscope is used for reading thei-icr onctr.

498. Bialkowsky, Harold W., and Probat, T. Richard. Dimensionalchances in paper. Paper Trade J. 111, no. 2:34-38(July 11, 1940);Tech. Assoc. Paners 23:246-250(Juni, 1940); Paper Ind. 22, no. 7:718,720, 722(0ct., 1940); B. I. P. C. 10:465; B. C. P. A. 1940B:738; C. A.

:''i 34:8275.

In a study of the of ect of' relative humidity on the dimensionalchnecao of paper, the papnr was humidified at 50p relative humidity and76 i'., placed in samnpi holders to accornodate strips about 25 cm.longC; (held taut by weights with a mass of 32 grams) and then in glasstubes, through which air was passed at a definite humidity (15 and 95%),

~ tthe rate being about 5 liters per minute; the elongation was measuredby means of a microscope (the accuracy was about 0.1%). Samples were

X ' also immersed in water at 23° C. for 1 minute and the elongation measured.Noernal bond papers change in dimensions about 0.6% in the machine direc-tion and 1.6% in the cross direction, when the relative humidity variesfrom 95 to 15%. The basio weight and. furnish seem to have little effecton these changes. The machine and cross directions change about thesame amount when the relative humidity is lowered from 50 to 15%; ifthe relative humidity is changed from'50 to 95%, the cross directionexpands about 7 times as much as the machine direction. There is nogeood correlation between dimensional changes caused. by varying therelative humidity and the expansion produced by actual wetting of thesheet.

I

flyzroexpa"Bivity - 176

'3 Davis, Harold S. New methods for measuring the effects oftenpcratu'e and humidity on the dimensions of paper. Paper 51, no. 12:7-2~, ).0(JYan. 10, 1923); World's Paper Trade Rev. 79, no. 10:804, 806(lvufii -CI4) I%53)yT. S:- 76:186;-c;. A;. 17:0~78.… --

- - --- Ar.- illuctra~tior and. a-briof description are c~iven of a conditioAninaet~arntus corsi-sLtrg of a glass tube 0.7,5 inch in diimeter~ and 3N'eetlong, th-ruugh which conditioned, air wad passed; the conditioning tubewas surrounded by a gJlass jacket through which water at any, desiredteupracrture couJld be passed. Paper strips 20 inches long were suspendedfrom adjustable supports at the top of the conflitioning~, tube and wereattached, at the bottom to aluminuni pointecrs. The pointers vere ar-

rne!so that each inch the pointer mo-ied corresponded to a change ofo.i% in. the lenQ~,th of the ropers. With constant relative humidity,the dinmolxjaions of the papers are substantially constant over a tempera-ture rapngeI of 70-lOW0 F. Vlhcni the absolute blimid-ity is decreased atba constant ttemnorature, thec dimensions decrea se and vice versa. Therato ct which the parer changeso its dimensions is denend~ent upon thlerate of' flow of the air over, it". The rate at which the raper increasesitfs dimensions vith ii s~ing relative humiility is somewhat greater than.the rate at ithich it Pecreases with falling relative humidity, but thediIS'erencc betwe-en the twoe is not very great. Tho rates at which thepaper charges its dimensions in a moderate current of air are fairlyrapid, being nearly complete in 5-10 minutes. The rtes are increasedwith rise in tempera Lure.

>00.- Davis, Raymond, and Stovall, htery, J., Jr. Dimensionalchanges in aerial photographic films and papers. J. Be0scarch Natl. BLor.Stondnrde 19, no. G-:613-637(Doc., 1957) (PP 1051); B. T. P. C. 8:209.

A machanical.ge or extoneometer was developedi for measuriing fiL11ohrikngcand, on- optical. extensomoter, suitable for both paper and- f i 22.

Ihe latter employs to C52-mon. M~icro-Tesriar objectives, one movable and,one f! ied. These lenues are- in fixed. focus or. thle u:pper surface of the

pia:~- glsstop of the instrument. Dy moans of Trrisms the beams fromthe lonnacs are brought to focus on a tu~nrfk-Irodhum photometric cube,which, brings the separate irxinges into juxtaposition. A brass tube fittedwi Lh a lens and hard-r-ubber cop with a smoll hole constitutes the eye-Piece of the instrument; this is focused on the photomeitric cube. At

the, riglht of thle boxc a micrometer is fitted to move the lens anid measureB ~ ~its disOplace-ment. At the other enC, of the box is a dial rage, whicalso indicates the position of the lenis. Either miAc:oronctc5. or dialCngo may be read.; the letter is preferable because of eave' of raigThe distance, between lenseGs is i$ inches.

CI.~ Deternination of the influence of moisture on, the dimens-ionsof paper. PapiCer-F&br. 22o:659(Oct. 190, 1924); 1'. S. 81:70.

The Sehopper test-Dr fo7' Jloterminrti, the influencecof moistutre onP,'ni)r is sketched cr4 dOcscrlhect.

j~L2. Griffin, Rotger 0. £'Zcflaruiofl of papor- wi th vrr-ryine humiditly. Pape-Trade J. 8,o55-hM.4, 1.927); Tech. Assoc. PThmors ll:8o-U5

(June1, 1928); C. A.- 211:4067; T. S. 86:193.

R

fly~ro0xpnnsivity -7 7

This in an extension bf the work Of H. S. Davis. An expanniometerhas bee-n designed, which cqnnists of a conditioning chamTber (a glass

tr 1.5 inches inside diameter and 2 feet long) which is cappedtoand bottlom with brass collars, through holes in each of which aru& placed

- -- -- two slid Irz. brass rode, adjustable. vertically by set screws end. ter-nhilrat.trnt2 at the( top anid bottom in clumps to hold strips of paper. The two Jlowe:' ronds a~re connected to two pointers, so counterpoiseDd as te

-puu-oract'icnaly; no strain on the paper strips.' Thle 1'unfl-ity of theailr in1 the chamber is controlled by thle use of the oroper crrtsu-14uric acid. solution. The pointers areo so designed that, with a1-0-inch strip of paper, cacli 'anall division en the scale correepordeto a change of o.oi% in the length of thle paper strip. If the paperis completely dehydrated and, then tested under increasing humidity con-ditions, more concordant results may be obtained and the paper coeisto equilibrium In. a imtch quicker time than wjhen the tests are startedat a h11gighr humidity and, tile humidity conditions are ciu'oequentlylowered. Thc results from teats on 12 different types of' paper showedthat the percentage elong~ation between 20 und 80% relative humidityis approxi~mntoea a straight line. The elongaltion is considerablygreeter in the cross than in. the machine direction. In most eases,the incronso in diongatuion between So and. 10oo hutaidity is considerablygreater than thiat between 60 anid 8o%.

50. Hamburgor, T. A flow arrangement for testing expansion and.contraction of paper. Parier.-Fabr. 229,. no. 44:693-696(Nov. 1, 1931);T. S. 05:152; B. I. P'. C. 2:11614.

Teapparat'us (designed by Riesenfel~d) consists of an airtightglass contanenr, which has a hair hyGrometer, a thermomecter,: ind a sampleof paner. 'The expansion and. cortrocti.on of the parer are rieasured at

diffrenthLani.LiticE.

H0.iurLton, Paul L., Carsun, ?roffer.ok T., and Kirkweood, P-1. S.Effect of atmospheric hvinlid-ity in the physical testinG; of 'paper. PaperTracle J. 76, no, 15:257j, 239), 2hl1 245,, 215, 2147, 249, 251Ari 2

195;Tech. Pasoc. Papers 6:614-71(Junc, 1-923); T. 3. 77:1; C. A. 1-7:2501.

Data are Given for the cxpansion and. con~traction.m of paper withhuŽ.~liditio-s of' 15 to 835e for 1.1 ropers. rfll readings were: made by mnean

* - ~of a microscope amounted. over a steel scale g~raduated in fifths of amijl-imcter. The effect is greate~,r in the- cr-oss thIan in,. the trnchinedirector. !Par the moat tart, thle culrves arec similar to thie moisture(Otcntor curvos. In some cases, there I~s a tendency for the rate ofchange to decrease with the higherhu dii.

2. Institute ofC Paper 0wnismtry. I-lstru:= ntationstde.X.Effect Of relative humidity on physical proneN'les with respect toULh hysteresis effect in change's from cor' huniffcity to another. Paper

1957:657 J.1, no. l5:1;5-kQ(Apri1 15,, 1937); B. I. P. 0. 7:314; B. C. A.193B:67;C. A. 31:4815.

Data are gi1ven showing the change in exponflion (in and. across),using 65% relative humidity as the base line, when the samples oarehUnlidified at 140, 50, 65, and 755S relative huml:~ity (ascendirg series)

* and at 75, 65, 50, anid 4'0% relatIve, humidity (descending series).

llygr~oexpnsivity - - 178

296. LTairocque, Gl. L. The extension of' paper by adsorbed watervancuvr. Pulp Paper Mac. Canada 37, no ). 84199-209(Miarch, 1936); Proc.TPech.- (lciou'a.Tlp Paper__Aaoc. 1936:83-94; C. A. 30:3641;B. C. A --. ;K*6E:_44q; B. i. P. c. 6:342; T. S. lb:3-_270t -- -

2':` zt ccors~.hted of.' strips of paberr 5e-m. wide and hocm-long k~.u L~ony the erosu direction of 'the paper), which were :coiled togivc cyll inders 4o cm. long and 1. on. in diameter. A piece ci rl r:kel.-stool wire, 0.01 eni. thick, was fastened at the top and anoti,0r- pi~ceof wire at;~ the bottoml,. or' the cylinder by means of sealing~ wax; thellower extr-emirties Of the two w~ire2 were in close, proximity to eachelother, and; their, dilstarco, apartU could bu measuared by El cothotomotetr.

lrthe measuroinorjt Of' the, rate of' expansion of paper by water vapor44n the absence of air, the sampnle tLas hung vertically inside a glasscylinder inmmersoa in a water bath at 250 C. and connected. with a sourceof' water vanor and a vacuum pump. A method is also described for the

k ~~menauroment of -the rate Of expansion in the presence cif air, themoisture being supplied by a stream of compressed air. A secondapparatus; was co:jstructed for the measurement of~ the adsorption Ofwater vapor by paper an-d the mn~nitude of the resulting extensionat various humidities. 'The equilibrium extension and. moisture ad-sorption took place, at the end. of about 30 hours, and no further change

NK ~was observed ait tho end, of 100 hours. Thcprimento were also carrIed.out withi the wet extension test of' TAPPI, in which the sample on ashoot of' clean plate g)lass was covered with a film of' water for 10minutes, after which the change in length was determined. Values arcreportoDd. for the equilibrium moisture content of 20 typical papers,as wlrl~l as- their expansion in both machine and croos directions, in an

rji~ 1'rOV 1OUorpincycle from 5 to 95% relative hurdldty and beck.

Thin rvi's lastrgel iscrevie of the woprko nlcodl rinffin, ans Witsor

Mnrin laiofa M.emc Exp otifot ond Ca~ntada JT. procedure fnor takiong

phays "cal tests of fibrem buildir,,; board. iqfC-19g-1940 (tentative).Jan. 51, 194g. 2 p.

Liner 7hnasir Th,: -laxirz*Im -inear empannion is determined fronto Specimen ~, x 12 inch.,L that heni been cult parallel with the longdirection of the board aid. fro~n a like specitisot cut at right orglesthereto. The expansion is maoenurod between two points approximately1.0 inches apart on the center line of' each specimen. Mhe specimensare C Onditioned for 24 hours at 505S2 relative, humjidity and measuremuntsOre' made Of the distance between the two rreferencc Points. The OpoCiflcroare; then conditioned for 24 hours at 97%1 relative humidity, after which!

....... - -

Hygroexpanaivity .. .179 .

the distance between the two reference points is again measured. The ox---- - -_ _ _- pension may be mnaoured by any convenient method, provided that the re-

salts are accurat6twithin 0.005 inch; - -Tho-nasuromonts oro ando in air,conditioned as specified in each case, or as quickly as possible aftereach specimen is removed therefrom. The linear expansion is reportedas Lth increase in length between the reference marks, expressed as-a -prcounthgoc of the length at 50% relative humidity. Sodium dichrorntonny bo used for an atnosphore of 50% and potassium sulfate for 97% relativehurlir .ty.

092. Ocl'eont, C., Wheeler, S. H., and Croncy, R. G. W. A ricthodfor -.icsuring the oxpannion and contraction of paper, etc., duo to changesin r.oi:turc content. The Printing and Allied Trades Research Assoc.,London, Tech. Paper No. 3. 1938. 32 p.

, 10. Reed, Robert F. The charactertistics of paper and their rola-tion to lithography. Lithographic Technical Foundation, Bull. No. 1

r (Resoearch Series No. 1). 1925. 11 p. Paper 'lTadc J. 3l, no. 27:45-46,*l (Dec. 31, 1925); T. S. 85:84.

Data are given for the average change in linear dimensions between35 and 65% relative humidity for 5 papers (the method used is not stated).Between 0 and 80% relative humidity, tho dimensions of a sheet of papervary in almost direct proportion to the humidity, according to oarlicr

vinostigaotors. The present results chock the percentage change across theUgrin, brlt parallel to the grain thero in a distinct difference. Thechanrg in oflfst paper across the rrain is front 4 to ;', tinms that inthu ruichinc direction.

',11. Roberts, D. The curling and waving of papers. Pulp PaperCanada' i:, no. 8:461-465(July, 1933); T. S. 98:158; C. A. 27:4923.

The percentage expansion was obtained by measuring the length oftrips of papers, cut in the machine and croas direction, at equilibriumwith air at 45% relative humidity at 75° F. and then by a second measure-

.on' of the length of the strips after equilibrium at 95% relativei'.lniidty at 75° F. The method employed a box in which the samples wereC.ri-ionred clams for the strips, and means for measuring the lengtho. she strips with no tension beyond that which was necessary to counter-

ince each movable clamp and keep the strip taut for the measurement.T.e results for 14 papers show that the greater expansion is always in!hs cross direction of the fibers.

.1 2 Scribner, B. W., and Carson, F. T. Study of fiber wall boards:"-' developing specification standards. Paper Tradc J. 89, no. 13:61-63

(Snt. 26, 1929); C. A. 23:5592; T. S. 91:84.

,An extensomeotr consists of a motal framework, at one end of whichI - p:votcd a lever, the shorter end of which bears against one end ofthe 0pecimon and the longer end serves as a pointer as it moves along theccnic. The scale is graduated directly ir percentage of a definite lengtho,; WLich the specimen is originally cut. The indicating luvcr is countcr-

';'' wVeigihtced to insure that it will always be in contact with the board.

I

Hygrocxpansivity -

At the opposite end of the framework there is pivoted on the frameworka second luver, one end of which bears against the end of the specimen.

-- This-Lcvcr.ie.adjustable to provide a means of adjusting the positionof the specimen until the pointer registors zero. -A-specimen so-ad- Juoted 1D an extensomctor and exposed to a relative humidity higher thanthat corresponding to'tho moisturecontent of the specimen will expandand push the pointer along the scale which indicates directly in per-centago the expansion of the board at any time. The expansion in thelong direction of all boards-studied was less than that in the shortdirection, the ratio'in the case of laminated boards being from 1/5 to 1/6.Data are given (for the short direction) for boards exposed to an atmos-phere containing saturated water vapor, after which the specimens wereimmersed in water for an hour.

513. TAPPI. Moisture expansivity of paper. TAPPI Standard T 447m-42. 1 sheet. Paper Trade J. 110, no. 13:28-29(March 28, 1940).

,;. Expansivity is the capacity to change dimensions. Moisture expan-sivity is indicated by expansion or contraction with increase or decreaseof moisture content, respectively. Practically the same value will beobtained by measuring either contraction or expansion, if conditionsare properly controlled. For convenience, the expansivity.is determinedby measuring contraction. The TAPPI Standard is based on the method ofWeber and Goib.

54. Van den Akkcr, J. A. The Neenah oxpansimeter. A method formeasuring the expansion or contraction of papers caused by change inrelative humidity. Paper Trade J. 109, no. 22:105-106(Nov. 30, 1939);B. I. P. C. 10:128.

*.: ^ A sensitive spirit level vial is suspended from the lower end of thetost specimen, which is cut in the form of along strip. One end of thevial is supported by the paper specimen and the other end is supportedby a pair of sharply pointed wire feet. The test specimen is supportedat its upper end by a simple micrometer arrangement. Tho lower end ofthe strip is naintainod at constant elevation by means of the spiritlovcl vial, and changes in length are measured at the upper end bymeans of the micrometer. The pitch of the micrometer screw and thelength of specimen are so chosen that the percentage change in lengthmay bc read directly from the micrometer dial. The constructionof the instrunont is described. A double system is used, so thathygrocxpanoivity for tlh machine and cross-machine direction may bemeasured -simultaneously.

515. Van don Akkor, J. A., Root, Carleton, and Wink;, Willncr A.·* Iltiplc-specimen Nocnah cxpansinoetr. Tech. Ancoc. Papers 25:351-354(Juno, 1942); Paper Trade J. 115, no. 24:33536(Dec. 10, 1942); B. I. P. C.13:153; C. A. 36:7314.

The original Nocnah cxpansinetor was designed to accommodate twotest specincno; the determination of hygroexpanolvity is intrinsically

'I"~g~~~~~PS"~"""lp--------··~~~~~~~~~~~PLYIW I --- . -t .

180

rygrooxpansivity 181

slow and therefore an apparatus has boon designed which will accommodate20 specimens at one tine. Detailed drawings are given for the nowinstrument. Each of the 20 spocirmns is suspended from a rod which

'· bears up against a micrometer screw. The specimen supports, in turn,-- -- --.- -one end of--a small spirit level vial. The other end of the vial is

supported by a short length of .003--inch-otool Fibbon, so-that a - - -vertical notion of the lowol' cnd of a specimen causes the level vialto'tilt. -With the lower-end of the specimen hold at constant elevation

- - by means of the level viol, change in length is measured at the top(to the nearest 0.0001. inch) with the micrormter. The metal supportingimnborc clanmpd at each t:nd of a vial have weights chosen in such a mannerthat very little force is required to lift the end of the vial supportedby the specimen. If it is desired to place the specimen under an appreciabletension, the required force is obtained by placing a suitable weight onthe connecting link between the lower end of the spccimrcn and the levelvial. The length of specimen between the lines of clamping is nominally10 inches. A method of maintaining constant relative humidity withinthe apparatus in discussed. Constancy of tcmporature is important.

2.6. Weber, Charles G., and Cobb, R. M. K. Register studies inoffset lithography. Bur. Standards J. Research 9, no. 3:427-440(Sopt.,1932)(RP 480); B. I: P. C. 3:38.

Changes in paper dinonsions were determined by means of a ruledesigned for measuring the displacement of reference marks on largesheets of paper. It is equipped with two magnifying glasses, each witha snail glass reticule having a vertical cross hair mounted directlyunderneath. One magnifier may be placed at any point within the rangeof the scale (24 to 64 inches) and readily set so that its cross hair-will coincide with any division on the scale. The other magnifier isset over the second reference mark by means of its micrometer adjustment.The distance between the reference points ray be read to 0.001 inch.-Eleven papers were conditioned and tested in atmospheres of 30, 45,65, and 75% relative humidity. Tensions of from 9 to 455' gram wereapplied to specimens 15 inches wide and the elongation for each incrementof tension was observed. The results did net indicate any significantd.ifferencos in elongation between the various samples tested. Thegreatest differences in the elongation of the different papers occurredat 75% relative hwurdity; the wiicot difference was loss than 0.1% forthe cross direction; differences for the machine direction were muchsmaller. The minLrimu variation between the expansions of the differentpapers occurred at %"5, rolactvc humidity and changes in expansion forchanges in relative humidity were of smaller magnitude in the vicinityof 45%,' than at other humilitics used.

517. Wober, Charles G., an.d GCib, Martin N. V. Now test fordimeonsioral changes in offset aDccro. J. Renoarch Natl. Bur. Standards19, no. 6:665 .673(Doc., 1957)(sP 1054); T. S. 108:145; B. I. P. C. 8:214.

The apparatus consists essentially of a wooden cabinet approximately40 inches high, 16 inches lido, and 12 inches deep (inside dimensions).The specimen is hold in clamps, the lower one being fixed and the upperone being suspended from a light flexible cable which lend over a pulley.

--- --

I*r' >*

Hygroexpansivity

Tension is applied to the specimen by a dead-weight load on the other endof the cable, the tension being equal to the difference between the totalload and that required to move the upper jaw. The pulley shaft extends.th ough the back of the cabinet and a mirror is mounted on the end outsidethe cabinet. Movement of the mirror, through rotation of the shaft,changes the position of a spot of light reflected by the mirror to agraduated scale near the baoe of the. cabinet.. Expansion or contractionof the specimen turns the shaft through travel of the cable over the pulley. Using the ratio of the radius of the pulley to the'distanceof the mirror from the scale, the change in length of the specimen canbe calculated from the travel of the liht bean on the scale. The samepaper was tested under dead-weight tensions ranging from 50 to 1000grams for the specimen two inches in width. Although increased tensionresulted in stretch of the specimen as indicated by the separation ofthe curves, for the range of tensions used, nearly all the stretchoccurred at humidities above 70%. Varying the tension from 25 to 500grans per inch of width did not change appreciably the slope of thecurve in the region belolr 70, humidity. Hence, if the expansivity istaken from this part of the curve, precise control of tension is notimportant. There is a possible error in the o:pans:inn and contractionof the cabinet crd. large variations in temperature during a test shouldbe avoided. A suggested method of test in appended.

218. Weber, Charles G., and Snyder. L. W. Reactions of lithographicpapers to variations in humidity and- temperature. Bur. StandardsJ. Research 12, no-. l:53-65(Jan., 1934)(RP 633); Vorld's Paper TradeRev. 101, no. 19:1502(May 11, 1934); Paper-IMaker 88, no. 4:311-312(Oct., 1934); B. C. A. 1934B:358; B. I. P. C. 4:161;.

The studies were made in a room of approximately 10o0 cu. ft.. inwhich humidity and temperature were controlled by means of a humidifying-dchiutnidifying unit capable of conditioning air at the rate of 2500 cu. ft.per minute, thus providing a change of air evory 3n seconds. Dimensionalmoasurcnonts were mado accurately to 0.002 of on inch on specimens24 x 24 irchos by moano of a micrometer rule. Within the range oi' about30 -to' 72.5T relative humidity, at 8300 F., the dimensions vary directlywith theo moisture content irresnoctivc of the causo of the moisturechange. The data obtained for different huiditieos with constant tempera-ture are. for different temperatures with constant humidity result ina single regular curve. The paper having tho geateot number of fibersparallel to the machine di.rction will have the lowest dir.onsional changein that direction, because this direction is parallel to tlhe diameter ofthe largest mnumbor of fibers. Coated papers hod the largest dimensionalchange per unit of moisture content variation and nachine-finished offsetpapers had the lowest. Surface sizing with starch increased the di-monsionIl changoc slightly.

il.

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1l2

153

IMPACT TEST - -- -

5t.1. Association of American Railroads. FreiRht Container 'Bureau.The inclined impact testing device. F.C.B. 673. Sopt. 15, 1938.

520. Dahill, Edward. Methods of making rough-handling test ofcontainers. _Fibre Containero 24, no. 4:38-39(April, 1939); abstractin no. 3:22, 38(March, 1939); Chem. Industries 49, no. 6:642-643(Nov., 1941); B. I. P. C. 9:473.

The principal faults of the revolving drum test are that it isdifficult to repeat an identical test and that a container is subjectedto chocks, falls, impacts, and stresses not encountered in normal handlingand in transportation. The test gives quite accurate results over along series of tests but this situation does not work out satisfactorilywihenl only one or two aamplus are available for study. -Tho need for:another typo of device lead to the development of the inclined impacttester. Some of the ideas considered in its deovlopment are outlined.The angle of the incline was selected as 10 degrooo; reasons are given.

| hThe max:imnm fall obtainable is 4 foct 2 inches and from this height,disregarding friction, which is present, the speed at the instant ofimpact is 11.2 miles per hour. The friction is so small in comparisonwith the force of the frcc-running loaded dolly that it need not beconsidered.

?1. Teow incline impact testing device. Fibre Containers 23,no. 12:40, 74(Dec., 1938); Converter 13, no. 4:22(April, 1939);B. I. P. C. 9:265.

A brief description is Givcn of thc tester.

522. Plaosanco, A.'V; Now fibro container dcvolopoionts. FibruCotaini.crs 24, no. 6:28-29, 63(June, 1539); Paper Dox and Bag Maker 88,no. 3:92-93, 89dl(Sopt., 1939); Sh'ars 57, no. 559:42-43(July, 1939);B. T. -. P. 9:577

The inclined impact testing device consists of a track inclined10 degrees to the horizontal. At the foot of the track :ts a stronglybraced bumper whooo face is 10 degrees from vertical, forming a rightangle with the plane of the track. The nackagos to bo tested areplaced, on a dolly with roller-bearing casters which run on the track.The loaded dolly is rolled up the track to a predetermined point and,when released rolls down the track at increasing speed until thepockago strikes the face of the bumper. The force of the impact isdetermined by the speed of the truck at the moment of impact, whichis practically constant for any given length of ran, and increaseswith the length of the run; it is proportionate to the aggregateweight of dolly and package. The package is placed exactly flushWith the front end of the dolly so that the impact will not beaffected by the package sliding on the dolly. The impact may beapplied to anir facc or any odge of the package by positioning it on

Bf�L�C�-----·I

Tnnaet Test l~b

the dollar. A movable hanrt( In the iform of a 4 x h-Inch-timber may be - -

attached to any part of the face of' -the bumper. This may be used toconcentrate the impact across the top or bottom edge or center of thepackageo or at any desired corner. The speed of impact may be correlated

- -- - -with Loirroaci; force o.C a freight; car in switching by the use of' a

Barees fin~ds that it is -x'ossbico to detcorrdno by this :aeene the ldntth of- rui c'ropodn to frediht car Impact at a given switching speed- niltu dcAlolcrnncwhcthior robthe corntain-r--wilj. give- protection-uncior- *h pc-o uwt r-o usually encountered. The weigh-b oft'iL co':mntent causes. the anckange to bond and twist, and the measure ofthis distortion cdetermiDncs t'he amount o' clearance or cushiioning

L marcccanary to ~)r:otct the, contents, or the extent to which the containerrizot bie s~trengthe1Lned. The dev-,ice oiccupies, a floor space ci' about2:; x 41 feet an Ti nter-ials for its construction cost about "'5C.

2% Quinn., Don. Conbur irrpact tarter. Fibre Containrcr 26, no.3:53(Morch, 2941); B. I- P. C. 11:331.

L ~~~The~ Conbur. tu~pact testnr isv essentially a dolly, running ein a 10-deg~ree inclined tracks, impacting a rigidly bunaper. t value, in addition,to, thu n iumle formi, Mooc in the n possibilityy of posritioining hazards ofvarious kinds oin the bairqier and also on the dolly. By' the use of theseattachments, there can be deve~,loped almost every sort of 'impact whichco-ntainers encounter in handling and, shipping. Its use is illustratedby the testing of containers containin g2 conned foods, in which it wasshown that the cones impacted sidewise tyithsteod about twice the forcesthey could withstand leng-thwise with appreciably loss denting-~ of thecans. Studies, hove indicated that far nore accurate measurements canbe obtained or the tear resistance of boards along horizontal edges

* than. is possible. with the revolving drum. By positioning a specified.load behind the coas, and by using; a standard -imp~act recorder en thedoily, 'the crush resistance of the cases under im:pacts can. be determinedtendI correlated' with the results of the Olsen crush tester.

52L. Quinn., Don. corbur ineline impact tester. Fibre Containers2,nc. :5(c.,194KV

'Pie besct useO of heri, incline Impanct touiter is to simulate th-e stresses:)-I' strains; Wh-ct crntciners enlcountejr whenstl e as a carl' cicil ii. freight

CCDS Whe a ierh car to impactedj, thercis. a distinct vertical asw~i as! a h or i zo~ntal I pact. a' -To cimxloat this condition, holes havocb>Žn;r drilled in, the i-clined- track about 12 inches apart and round headedcarriageo bolts width washers inserted, in these holes. When the deity

tfIr dwni the track, there i~s a series of vertical impacts, followed by-~tro dfinit horizontal impact. TIt is probable that there should ber a)h-don top and on cbhind, the box beingiC tested.

).Quimi, Don L. Wo(,w container testinG deovices. Pacricar!'Ianagert~ntL Association, Iteduction 2x.ri cs No. 115 :36-4o(1959).

4 . ~~This article is concerned princinailly with the inrcline impact tester.* - The test sirmlates the destructive Threesc of' freight car irtpacts, 95% of

WhIch Occur in yards anti 5%;o in trains. This test should be used if the* 4~W' ContLainer mo.ve--s in carload iota, whereas the drum test should be used. i-f the

Impact Test _

container is to move by parcel post, express, or local freight. Certainmodifications of the test are possible. As an example, a plank positionedon the face of the bumper so that it contacts the extreme top edge or

- th- extreme bottom edge of the container at-impact will. simulate the .forces of a direct drop on the edge and sot up an edgewise diagonalstress in the container; a small block positioned so that it contacts

, ilthe container at impact adjacent to the corner will establish a strainsimilar to a corncnriso diagonal compression test.

;?> >26. Rcod, E. 0., and. Veitch, F. P. Impact tester for fiber board.Paper 24-, no. 21:24-27(July 30, 1919); Fibre Containers 4, no. 9:8-9(Sept., 1919); C. A. 13:5010.

Because the determination of the bursting strength does not givesufficient information concerning the strength of fiber board under. ';-'ico conditions, an impact tester has been designed for the purposeof establishing minimrum impact requirements for the different weight orthicknloes of boards. The tester consists of a two-kg. hammer, whichis -uidod by two vertical rods. The upper end of the harnmr is so

constructed that it con be held in position and roleasod from a crosshead

which can bo -o.cd up and down the'guide rods and locked in position byset screws. The right-hand guide rod is graduated to 0.5 cm. and isadjustable to allow for variations in the thickness of thd boards tested.By raising or lowering the crosshead the hammer may be adjusted to any

desired height above the plunger. The plunger weighs one kg. and has a

spherical lower end, the diameter of which is 2 cm. The plunger rests

in the center of the fiberboard to be tested, which is clamped underthe clamping plate operated by a lever, in the center of which is acircular hole 6 cm. in diameter. A hole in the base of the tester of

the same diameter corresponds exactly to the hole in the clamping plate.

'Th!is p3 te is 5 x 7 inches and, because of the large clamping area,the booad may be firmly clamped with but little pressure and withoutcrushing the board. The test strips are 5 inches in width. The burst-

igi; height is the distance at which the hammer Just drives the plungerthroul'!i to the shoulder of the bovel. There is practically no parallel-io-n b-twcon the results with the impact tester and those with the llullente tor.

527. Swocnoy, 0. R., Hartford, Charles E., Richardson, Roger W., andWhittemoro, Edward R. Experimental studios on the production of insulatingboard from cornstalks. Iowa State College, Iowa Eg. Expt. Sta., a1ll.102. June 10, 1931. 64 p.

Impact Test. The tester consisted of a vertical steol rod support-;'- inr two horizontal steel arns. The lower arm was sat with the under

cido at zero. The upper arm was set at the desired height for the test.

: - leTh cover on the test cup at the bottom was replaced by the board to: * sf;. bc tested. This cup was adjusted so that the zero setting on the peeon

,'* ',;, , rod resting on the board was zero. A weight attached to the upner rm

· i '..:. .wat cllowvd to drop to the top of the peen rod. Tho ii.dortnat;ion ir. the

.- board under the force of the falling weight was read from the gradua--

%: :;^~ .tiJnn on tho peon that project below the lower face of the fixed arm.

· ·L-Y�C�glldf�e��ri�*Unrrrrul-**I�1I�L

185

Impact Test - .

528. TAPPI. Impact resistance of fiberboard shipping containers.TAPPI Standard T C01 sm-44. 2 sheets.

''hc..imnact resistance of fiberboard containers or boxes is an ''arbi'trcry measurement of the energy required to ruptue-e the box byimpact when successive blown of increasing--'crce are applied- in theprescribed manner. The result is expressed as the fina L distance,in feet, travelled by a dolly, carrying the loaded box, along aninclined plane to a bumper before rupture of the box occurs. The deviceconsists of the incline impact testing device developed by the FreightContainer Bureau.

5'2°. Werner, A. W. Manufacture of fibre shipping containers.Chicago. Board Products iubl. Co., 1941. 70 p.

inclined LmLpact Tester. Since impact is the aoulcc of most failuresto containers in transit, a device was recently developed which is in-expcnsivo and simple in operation. With it the intensity of impact canbe controlled and repeated ao often as desired. Full sized containers

;: arc subjected to test with the intention of recording the effects ofjt shock on the container itself as well as on the contents amd cusiioning!~ materials used on the interior. The dcvico consists of a long inclined

runway having stool tracks and a rise of 4 ft. 2 inches. A ball bearingequipped wheel truck or dolly capable of carrying the largest container,runs on this track. A bumper block is located at the base of the runway,having sufficient strength to resist repeated shocks. The angle of

,K? the runway is 10 degrees and the truck wlhcn started at the top attainsa speed at instant of impact, disregarding friction, of 11.2 miles perhour. Toats are seldom if over conducted, starting at the top becausedestruction of the contairor wonlid be aosured. Thcreforer markings

j-, along th-_ track arc desirable so that tests can be rcpcstcd from a·;'" definite point. Srlow ot'o7n mo-ing pictures record cprmiinoetly the

exact co-nditionj Cxisting3 at the moment of impact which can be studiedanytime later and in absolute detail. Further than this, these picturerccordc arc of considcrablc valuc when comparing conditions on similarconta'iers, tests on, which arc run at various times. When. rigged withnroncrly located scales, within focus of the camera, the distance inwhich the shock is absorbed can be recorded and the efficiency of theinner packing determined. The container to bc tested is placed onthe truck or dol.v and by mcons of a small winch or rope block the truck:i pmtllud up the :t,'Uete to t;ic desired starting point where it is ro-leased. Being acted upon by the force of gravity only it attain aspeed connensurate with the starting position and each successive test,weights b',ing equal, will produce identical irmpnct-.

I

187

PUNCTURE TEST

529A. American Society for Testing Materials. Tentative method_ .. of test for puncture and stiffness of paperboard, corrugated and solid

fiberboard. A.S.T.M; Designation D-781 --44- T A;S.T.M. Standards-- .1944, Part III:1342-1345.

This is the same as TAPPI Standard T o05 m-44.

530. Beach, R. L. Evaluation of fiberboard box quality by labora-tory testing. Unpublished mss.

The three vital factors in fiber shipping container quality areresistance to crushing, puncture, and tearing at score lines. The author

i ~ indicates that these three properties can be measured by the Beach punc-ture tester. The comparative stiffness of combined board or solid

C: fiberboard can be measured by the puncture tester and, when made ondifferent grades of board, should parallel results obtained on tubetests or compression t9sts on boxes with uniform fabrication from thesame grade of material. The puncture tester, constructed with differentweights to give varying amounts of energy and having an accelerationand deceleration produced by gravity alone (except 'or the comparativelymall percentage of the total energy absorbed in puncturing the materialbeing tested), would seem to be the simplest mechanical apparatus formeasuring the resistance to puncture of all grades of boxboard material.Actually, it has been found that the results are comparable for allgrades of material from 9-point corrugating material to 600-lb. MTdoublo-wall corrugated board and are independent of the fiber forma-tion, depending solely on the basic fiber strength of the materialbeing tested, weight per 1000 sq. ft., and the stiffness of the material.The puncture test results will parallel the Mullen test results onboards having the same fiber formation and rf.rnish. The puncturetester makes three tears, approximately 1.5 inches in length and atangles of 1200, proceeding from a central point, irrespective of thegrain direction of the liners or the corrugations. The numericalresults are a sum of the tear resistance and stiffness of the materialbut either factor can be eliminated to determine the other; consequently,the puncture tester is a definite measure of tear resistance of scoreline strength of all grades of box board and has the additional ad-vantage of tearing the corrugating laedium simultaneously with the liners.

>31. Beach, R. L. Puncture testing of box board. Tech. Assoc.Papers 22:240-245; discussion, 40-41(Juno, 1939); Paper Trade J. 108,no. 5:30-35(Feb. 2, 1939); Fibre Containers 24, no. 3:42-44((March, 1939);Papicr-Ztf:, 64, no. 56:1219(July 18, 1939); B. I. P. C. 9:287; C. A. 33:4027.

The desired features of the instrument wore: (1) rapture a consider-able amount of material to avoid small variations; (2) rupture all con-ponents of combined materials equally and, as far as possible, nimultan-

';-S eously; (3) rupture along defined lines so that the rupture would be}[. independent of such factors as grain direction and direction of corrugations;

Puncture Test 188

(4) rupture in a sufficient number of different directions so that theresults would be an average strength in all directions; (5) itself haverelatively few inherent variations because of friction, gages, andsprings; (6) be calibrated in definite units of energy, and which couldbe duplicated and checked without elaborate apparatus or difficulty.The final apparatus involves the use of a pendulum, on the end of which

-- is fixed a rod bent-in the form of an arc of-90 degrees. To the end ofthe rod is affixed a metal point having the shape of a triangular pyramid,one inch in height. Advantages of the pendulum principle are listed.The test specimen (corrugated board or similar material) is held betweentwo clamping plates which are approximately at the level of the axis ofthe pendulum. The upper plate is fixed and the lower plate is held byspring pressure against the material. The pendulum is held up by atrigger and stop in a horizontal position. If there is no materialbetween the clamping plates and the trigger is released, the pendulumwill swing through an arc of 180 degrees to the horizontal position,except for a small retardation from friction; this friction is compensatedfor by an adjustable stop against the pointer. If material is betweenthe clumping plates, some of the energy of the owing will be used up bythe puncturing point punching through the material and, consequently, thependulum will not swing as far as 2.80 degrees by the amount of energythat has been used. The pointer remains at its maximum reading positionby a simple friction bearing. There are no variables in the apparatusexcept the friction of the bearings and the pointer sleeve. With theuse of high-grade ball bearings this friction is constant and very small.In the model described, the bare pendulum weighs 9 pounds and the centerof gravity is 5.43 inches from its axis, so that its potential energywhen in the horizontal position is 48.87 inch-pounds; additional loadsare provided to give total potential energies of approximately 87.9, 183.25,and 357.5 inch-pounds. The apparatus will test materials ranging from0.016-inch liner board to combined solid fiber or corrugated board ofthe heaviest grades manufactured. In order that the apparatus givecominparblo results when used with different weights, it is only necessaryto keep the velocity of the puncturing point practically uniform, otherfactors being constant. Much of the energy of the pendulum is used inbending the specimen so that it is also a measure, to a certain degree,of the stiffness of the material. By cutting a '"Y in the materialbefore making the test, with each leg of the Y slightly longer than thetear which will be made by the point in its usual rupture, the stiffnessof the material alone can be measured. The chief reason for choosingthe triangular pyramid form of point was that it duplicates the cornerof a box, the angle formed by the edges being 90 degrees. licsults oftests arc given. An appendix by E. H. Hull gives the theory of thecompound pendulum as used in this type tester.

52. Beach, R. L., and Coloby, L. Study of variations found intesting of corrugated boards. General Electric data folder 3528. Nov. 1,1939. 9 p. Charts.

The tests were carried out on three types of boards: one with a42-lb., dry-finish Fourdripier on both sides and 0.009 kraft corrugations;one with 90-1b. 0.030-inch Fourdrinior kraft liners; and one with 95-lb.

. H

Puncture Test 189

cylinder kraft liners and 0.009 kraft corrugating sheet. The materialwas conditioned at 65% relative humidity and the tests were made con-tinuously within the space of a few hours by an experienced operator.Five hundred tests were made. Puncture tests were made half with oneleg of the puncturing point parallel to the corrugations and the other

": half with the leg perpendicular to the corrugations.' The curves for -'.l, ~the 42-lb. Fourdrinier and the 95-lb. cylinder kraft boards lie quite

I' - - close together; there--are exactly the same number of tests having zero. ~deviation from the average for both materials and the spreads (including

100%' of the tests) are so close together that the points cannot be dis-~ ~tinguished on the curve. The values arc 10.8% for the 42-lb. board

and 11% for the 95-lb. board. The number of tests necessary for 99%probability are:

$t &Possible error, 42-lb. 90-lb. 95 lb.% Fourdrinier Fourdrinier Cylinder

7 ' 6 5 45 9 8 63 19 18 112 37 32 20

555. Eckhardt, Henry C., and Snyder, Lco W. Study of the Thwingimpact tester. Paper Trade J. 86, no. 15:64-66(April 12, 1928); Tech.Assoc. Papers ll:91-93(June, 1928); T. S. 88:199; C. A. 22:3297.

In the Thwing impact tester, a heavy plunger, falling in verticalguides, punctures the specimen by its impact. The work done in piercingthe specimen is determined from the initial energy of the plunger andthe compression of the nDrings placed at the bottom of the guides, whichabsorb the remainder of the energy left in the falling plunger afterthe specimen is pierced. A description ani, illustration of the testerare giver. Tho formula for the calibration of the inEtrument isdeveloped. With the oxcuption of papers which' stretch irordinotely,the strongest material which actually can be tested is one requiringabout 77 inch-pounds of energy in being punctured. The tester wasdesigned to test heavy boxboards which, through service conditions, areoften subjected to direct impact such as this tester is intcndcd tosimulate. Because of the manner in which the data arc e::prossed, theresults are not directly comparable with those obtained with any otherPa -per-tcsting device. However, results obtained with the Mullonbursting strength tester are included, because it was thought thatthe two instruments might grade a series of papers in the sami order.Tests with kraft wrapping paper showed that the order in which thes amples are graded is different for the two testers. One reason for

" K-.. this is the nature of the test. In the Mullon tester, the specimeni^'1. is ubjectcdl to a uniformly increasing pressure until it bursts; in

the Thwing tester, the specimen is subjected to a direct impact suffi-.p> cient to cause its rupture. Another reason for the differences is

'* . that the capacity of the impact tester is too high for this type ofP, aper. In. tests on heavy boxboardo, the moan porcontage deviation

': '-. of the individual test values from the average values obtained with.', the impact tester is lower than that obtained ,wth the iullcn tester.

-_

-_ . Puncture Test 190

This is an indication that the impact tester is capable of producingconsistent results. Forreadings on the Mullon tester from 100 to 300points, the approximate relatior--Thwing impact value = 0.156 Mullen

-- ' bursting- points--holds- withi-n-about 15%- of the-observed. values. TheThwing tester is not suitable for testing single plies of light weightp. .pr, because the resistance of such paper is insufficient to give anadequate scale reading. 'iTh significance' of the results in terms of - - --- -secrviceability of the board can be determined only through extensiveexperience.

534.' G. E. announces now box board tester. Paper Trade J. 117,no. 12:33(Sopt. 16, 1943); Paper Mill News 66, no. 38:25(Sept. 13, 1943);Paper & Paper P'oducts 85, no. 1:12(Sopt. 20, 1943); Fibre Containers23, ro. 9:26(Sopt., 1943); Instrumental6, no. 10:651-652(Oct., 1943);Paper Ind. 25, no. 7:808, 810(0ct., 1943): D. I. P. C. 14:43. Cf. alsoPaper Tradc J. 119, no. 1l:16(Nov. 2, ].944); Papor Mill. News 67, no. 45:60(.Nov. 4, 1944); ibrc Containers 29, no. 10:78(0ct., 1944).

This relates to the Beach puncture tester. The tester will doter-mine the strength of boxboard from 0.014-inch liner to 0.140-inch solidkraft, as well ac waterproof boxing material. It will also measurethe strength, without deformirg. or flattening the corrugations, ofcorrugated board of various grades. The tester consists of a pendulumon the end of which is a rod bent to form an arc of 90 degrees; the ,point is shaped like the corner of a box to simulate actual shippingconditions. The unit holds the material to be tested firmly betweentwo clamping plates which are level with the axis of the pendulum. Thependulum is operated by a trigger and, as this is tripped and thereleased pendulum savings through its arc, the number of dereeoos lossthan 180 degrees through which it swings is a measure of the energydissipated in puncturing and bonding the test sample.

535. generall Electric Company. Punctu-re tester (Cat. No. 8257564G1).GEI-20213. Juno, 1944. 7 p.

A brief description is given of the puncture tester, formerly knownas the Beach ?urctvu-e tester and also known as the G. E. boxboard tester.It La desigL'ned for the measurement of the stiffness or the resistance topuncturc of fiberboard and similar material. The energy possessed bythe bare pon;lulum is not sufficient to enable it to puncture strongmaterials, and auxiliary weights are supplied which increases theca-ac'ty of' the instrument 2; 4, and 8 times. The test procedure is

--.>'. outtlioed. The samples should be placed in the clamping plates in such" a mannel that o.n nns-. ha]' of' the tests the leading edge of the puncturepoint makes a t.sr in one direction of the material and, on the other

,:; he half of the ' estn, in a direction perpendicular to those tears. Thepuncture point should hit on the outside liner of corrugated board and

.', on the smooth side of the uncombined board. If low readings are ob--t^: ' tainod, they are not necessarily the result of poor fiber strength but

ay bo caused by any one of the following conditions: poor liner ad-hesion; crushed corrugations; poorly shaped corrugations; poor quality

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~ Puncture Test 191

of corrugation. Instrumental maladjustments, such as an unstable founda-tion, too much pointer friction or tightness of pendulum collar causehigh readings. Making tests too close to the edge of the material ortoo close to each other on the surface of the material also may be the

-- reason for high readings. General-ly, however, high-readings are the_results of tests made on an unusually sound area of the sample.

56. Hull, E. H. Theory of compound pendulum as used in pendulum-type puncture tester. Appendix to article by Beach (No. 531).

| -.7 Institute of Paper Chemistry. Beach puncture tester. ReportNo. 53to American Paper and Pulp Association, Aug. 24, 1943. 15 p.

The Beach puncture tester, an instrument for measuring the workC : required to pierce a paperboard with a pyramidal point, has been investi-

gated as regards principles of method and design. Fundamental measure-ments made upon the instrumental constants and scales showed the latterto be accurate. Fictional losses were found to be small and of suchnature as to be allowed for, with one exception: an appreciable lossoccurred from the method of mounting the auxiliary weights. A signifi-cant error was found in the displacement of the release mechanism whenthe auxiliary weights were added to the pendulum system. Strain-energy set up in the puncture arm was found to result in appreciableerror. The effect of sharpness of the edges and point of the puncture head

-'~.'9 was investigated for a number of boards, and a consistent relationship.';-- ' between test r-oults and sharpness was not found; this led to the con-

clusion that, whatever the ultimate significance of the instrumentalB^' : reading, a difference between a pair of readings on different boards

tjs'. is not significant. The influence on test results of thin films of!Ff':, tacky and lubricating materials was measured; it was found that theif^ nature cf the surface of a specimen could, under certain conditions,

i:11;". affect the puncture work quite natorially; doubt is oxprossod thatdifferences of this origin reflect the relative abilities of two

ihtte- boards to withstand puncturing forces. The effect of varying the size~K o' and angular orientation of the triangular sample aperture was observed

:X^^ 1.~ with the view of establishing manufacturing tolerances on these variables..~K^ i,!. Results are virtually independent of the angle between sample aperture

-ItR^'- and puncture hcad for angles up to about 7 degrees. Specific sugges-$ K. $ tioeo are made for improving the instrument.

2~8. Plcasanceo A. V. New fibre container developments. FibreE . Containers 24, no. 6:28-29, 63(June, 1939); Paper Box and Bag Maker 88,

no- 3:92-93, 89d(Sept., 1939); Shears 57, no. 559:42-43(July, 1939);'); B. I. P. C. 9:577.

..v4i4 The Boech puncture tester is a very simple mechanism, essentiallyg ;Wtfi'.' pair of claepirE plates which hold the board with crushing while a

fE i;pointod pendulum swings against an exposed section of the board. The~' ~ tPtndClum1 has a point in the form of a three-sided pyramid with roundedE O'?80, si, smulating the impact of the corner of a wooden box or similar

'i ^- ,c~tengeulaar object. The amount of energy required to force the pointE l^!tt1 O'gh the board is read directly on a scale. For testing different

A Pdes of board, various weights arc attached to the pendulum ard thereS .~,~ e a different scale on the dial for each weight.

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the container under consideration. It is acknowledged, however, thattwo series of tests (such as are herein discussed), extensive and time-consuming as they may be, are obviously inadequate for the establishment of

- fundar-ental principles or rigid.rules for procedure, and that the studiesshould be extended to include every type and make of flat stock, ad-hesive, design, fabrication, and combination encountered in the industry.

541. Werner, -A .W. Manufacture of fibre shipping containers.Chicago. Board Products Publ. Co., 1941. 70 p.

Punctilre Resistance. The resistance to puncturing is usually testedby cropping a pointed object from a predetermined height on the face ofthe box and observing the extent of the failure. The amount of punctur-inc will depend upon the size of the box face and the quality of thebonrd as well as upon the nature and weight of the point. Comparisonsobtained through testing boards of a standard size are more accuratethan those obtained through testing the faces of completed boxes.

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SCORE TESTS

542. Carlson, Thorwald A. Apparatus for testing fiber board.U. S. patent 1,612,415(Dec. 28, 1926); Paper Trade J. 86, no. 2:59-60-(Jan. .2, 1928); T. S.-85:241;-87-:72..-

The apparatus comprises moans for applying a combined action oftension, tearing and repented bending to a specimen while it is bent-over and drawn firmly against a sloping edge. In-the case of scoredboards representing material from an edge of a fiber box, the speci-men may be bent initially at an angle of approximately 90 degrees, thebend being parallel to and at the score, so the score may be in contactwith the sloping edge during the test. The number of times that thetest piece is bent through a predetermined angle, together with themaximum tension applied before it is torn apart, is taken as an indi-cation of the amount of rough handling which the finished box willwithstand. The stationary clamp of the instrument consists of anadjustable jaw mounted on a fixed jaw having an extension in the formof a plate with a transversely sloping edge over which the test speci-men is bent. The other clamp is carried by an oscillating arm whichis equipped with mechanism tending to stretch the test specimen bydrawing the clnam away from the axis of oscillation of the oscillatingarm. The letter is mDved back and forth through the desired angle.The two clamps are so placed that when the oscillating arm is in itscentral position the planes o tLhe clamping surfaces are at right anglesto each other, intersecting, if extended, in a line approximately atthe axis about which the oscillating arm oscillates. In making thetest the specinmn is bent over the sloping edge, which is approximatelyon a line through the axis of rotation of the oscillating arm, and theends of th., test piece are held by the two clamps, so that the positionsimulatciL th.-c iIn which tIe material is placed in a sot-up and loadedbox. The tost piece is bor-t back and forth at the sloping edge andthe tension caused by the force applied to the movable clamp causesthe specimen to tear along the sloping odgc. Ty using, for the ex-tension of the fixed jaw of tlhe tationary clamp, plates terminatingIn edges having different slopes, the severity of the test can be varied.Suitable means arc provided for determniing the number of bonds and themaximum tenrioTr which the test piece sustains before failing.

54j. l'laskott, C. A. Principles of box and crate construction.U.. S. Dpt. As-. Tech. Bll].. No. 1.71. April, 1930. 151 p.

Fiberboar-d Score Te--t. A snccilon containing a scored edge is cutfrom the bo:. and tostcd in. combined bending, tearing, and tension. bymeans of tl. score tester. On the machine aro two clamps, one mountedon a Gtatioimrr inclined lodgo at the top and the other on an oscillat-ing ar. Tilis rm is connected with a driving mechanism by moans ofVlich it can be .madc to swing through various angles and at differentBpoeds. The movable clanp is conrccted through a calibrated compressionspring to a screw and ratchet !olel which causes a downward movement

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Score Tests 195

of the movable clamp when the oscillatfing arm moves back and forth. ' The test specimen, which is 1 inch wide and'about 4.5 inches long,has the score midway between its ends and at right angles to itslength. It is first bent through an angle of 90° at the score and isthen clamped in the machine with the score resting at the slopingedge at-the end of-the cxtcnsion oif tho lower jaw of the stationary _clamp. Thus, when the machine is in motion, the specimen is bent backand forth at the sloping edge, and the tension caused by the forceapplied to the movabb cldamp-causes the specimen to tear-along-tthesloping edge. This action simulates the conditions which are on-countered by the edgos or scores of a loaded fiber box when it issubjected to rough handling or to the skewing and racking caused bythe swaying of a moving freight car. The test is continued untilthe specimen fails, and the maximum pull and the total number of bendswhich the specimen withstood are taken as measures of the ability ofthe box to withstand rough handling. The degree or intensity of thetearing can be changed to simulate different conditions by modificationof the sloping edge, together with the possible variations in speed,angle of swing of the oscillating arm, and rate at which the tensionL.isincreased. A combined boeding and tension action without tearing canbe obtained by using an cdge having a horizontal ledge over whichthe tension and bonding is applied to the specimen instead of a ledgehaving a slope or inclination.

_44. Quino,'Don. Simple strength property tests. Fibre Containers25, no. 6:41(Juno, 1940).

A description is given of the "Eullen strip test." It is similarto the toot described in the following abstract. Test results and, forcomparison, drun tests are given for four boards.

Lot Strip Test, Drum Testslb. Falls

1 83 312 120 563 125 654 148 97

245. Quinn, Don. Strength of corrugated containers along creasedodges. Fibre Containers 26, no. l:41(Jan., 1941); B. I. P. C. 11:216.

If one box has cylinder-foracd liners and the other has Fourdrinier-fornod liners, the bursting strength is not a very dependable criterion oftheir retention of contents strength properties (this is defined as

' that property of a container which enables it to hold the contentsintact as a unit during its life of service). The operation of creasingdepreciaten the strength of a board. Thus, the standard burstingtest, which is made over uncroasod sections, is not a criterion ofthe strength along the edges. The following method is suggested. Usethe the standard Mullen or Cody machine. Cut the strips 1-1/8 inches

i> Wide. This width of trip can be positioned over the orifice of the

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Score Tents 196

tester without danger of either edge contacting the edge of the orifice.One sot of strips has the corrugations perpendicular to the length ofthe strip, the other has the corrugations parallel to the length. Ineach instance, the creased edge lies across the width of the strip.Position-the creased-edge exactly over the center of-tho-rubber _diaphragm of the bursting tester. The clamp pressure must be tight,otherwise slippage will occur. The outer facing should be up inthis test. If the specimens are cut from bbxes with vertical corruga----tions, the strips with corrugations perpendicular to the lengthrepresent the vertical edges and those with corrugations parallelto the length give the record for the horizontal (flap) creases.

546. Werner, A. W. Manufacture of fibre shipping containers.Chicago. Board Products Publ. Co., 1941. 70 p.

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Score Tester. Investigations have clearly demonstrated the needfor a test on the scores of fiber boxes, since the strength of thescore appears to depend more upon the condition of the board at thetime of scoring and upon the scoring process than upon the quality ofthe board. A fiberboa:d ccore tester has been designed by the U. S.Forest Products Laboratory to test the score of a fiber box. A speci-men 1 inch wide and about 4-1/2 inches long, containing the scoredridge midway between the ends, is cut from the box and by means ofthe testing machine, the sample is tested in combined bending, tearing,and tension; the action of the machine is quite similar to the forcescausing failure at the scores in actual service. Tests on the scorededges of the box are especially valuable for determining the efficiencyof the scoring process.

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197

SERVICE TESTS

i47 Jiggle tester.- Fibre-Containers 25, no. 3:56(April, 1940);-B. I. P. C. 10:398.

P .i.The Jiggle tester (illustrated) simulates the jogging and bumpingmotion which shipping containers receive riding in freight cars and motor

L trucks. One or more loaded containers are placed on a suspended platformto which motion is imparted by means of a series of rotating cams care-fully timed so as to produce various combinations of vertical and lateralmovements in a definite sequence. The speed can be regulated so as toobtain a slow jogging motion or a rapid vibratory action. Containersare subjected to this treatment for a definite period of time and thenexamined and tested to determine the effect on case rigidity, bondadhesion, etc. It is believed the test will be particularly valuablein detcrmining the effect of prolonged vibratory motion on the adhesivestructure of corrugated boxes.

548. Plaskett, C. A. Principles of box and Crate construction.U. S. Dept. .gr., Tech. Bull. No. 171. April, 1930. 131 p.

The weaving test is designed to simulate the side swaying or rollingof a moving freight car, or the repeated starting and stopping of a car.The swaying action of a train is reproduced on the testing machine byan oscillating table or car, which can be made to move horizontally for-ward and backward at different speeds through any distance up to a maxi-mum of 8 inches. The box to be tested is fastened rigidly to the tableby clamps along two of its bottom edges and a weight equal to the averageload carried by a container in the bottom tier of a loaded car isfastened on the top. When the machine is put into operation, the con-tainer is carried back and forth with the movement of the table. Thistest affords a means of comparing boxes with respect to their rigidity,which is indicated by their resistance to weaving or skewing. The testmaf be continued until complete failure occurs but usually the boxor crate is tested on the machine until the joints are loosened andthen it is taken to a drum-testing machine.

Impact-Shcar Test. The oscillating table is used also to simulatethe starting and stopping action of a freight car, which produces animpact shear in the container. For this test, the box is suspendedfreely and above the table by two metal straps. The supporting strapsform a parallelogram suspension and horizontal guides, fitted withrollers to reduce the friction, allow the box to swing only in thedirection of its length, which is parallel to the motion of the table.Two stops are fastened Oscurely to the table and the ends of the boxstrike against them as the table moves forward and backward. Any

M- j LM desired weight may be placed on top of the box during the test. Thenumber of complete oscillations of the table before failure of the boxis indicated by an automatic counter.

190

SMOOiTNESS

--- -549r- Advancos- in the surface testing of paper. -Popier-Fabr.--32,no. 41:428-429(0ct. 14, 3934); B. I. P. C. 5:95.

Reference is made to the comparison microscope of E. Stach, -

which has been modified for testing surfaces of paper, etc. Illustra-tions of two kinds of paper.are given.

522. Barnhart, John W., Baumruckor, William, and. Dodge, William G.Apparatus for determining the surface texture end finish of variousmaterials. U. S. patent 2,056,315(April 7, 1936); T. S. 103:380.

The apparatus is constructed to measure the contact pressure re-quired to cause slippage botwven two contacting surfaces of the materialunder test with a predetermined torque, the smoothness of the samplebeing measured as a function of the pressure exerted to prevent slippage.

5_1. Beazley, Warren. The measurability of printing quality. PulpPaper Mag. Canada 41, no. 2:117-122(Feb., 1940); Proc. Tech. Section,Can; Pulp Paper Assoc., 26th Annual ?teting, 1940:98-103; B. C. P. A.1940B:351; B. I. P. C. 10:254; C. A. 34:3087.

The Bokk, Williams, and Gurley testers are modifications of the air-leak method of measuring smoothness. From the standpoint of testing 'theprintability of paper, these testers arc open to the following objections.In the Williams tester, th3 pressure of 14 pounds per square inch is inno way comparable with printing pressures which are of the order ofhundreds of pounds per square inch; because the paper is clamped betweentwo herd surfaces, the paper is not subjected to the same forces Eathese which arc produced on a printing press. The Gurlcy tester is opento the same objections. The Bckk tester is subject to the first of theabove objections but is Yfrc of the second, because the rubber is thecounterpart of the backing or blanket which is used on the cylinder ofa printing press. These instruments measure a smoothness but not theright kind. The author discusses general objections to the air-flowmnthod of measuring ormoothnees, and points out that the real requirementis some measure of the number and size of spots which lie below a plane,the position of which, relative to the paper, is fixed by the pressureconditions specified.

_25. Bekic, Julius. Apparatus for measuring smoothness of papersurfaces. Paner Trade J. 94, no. 26:41-412(June 30, 1.932); Paper Mill55, no. 358:4, 6(Sept. 17, 1932); T. S. 95:222; C. A. 26:5206.

The Bekol smoothness tester is illustrated, and its method of. operation is outlined. Data arc given showing the reproducibility of the

- results and values for nine types of paper. The apparatus may also be5,'; used for the determination of the porosity of paper (results are giveni -.i !for 13 types of papers).

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55. Brecht, Walter. Methods and instruments for testing thesmoothness of papers. Papier-Fabr. 30, no. 29:457-463(July 7, 1932);Wochbl. Papierfabr. 63, no. 22:419(May 28, 1,32); Zellstoff u. Papier12, no. 6:265-266(June, 1932); Boll. staz. sper. ind. carts 12, no. 1:4-6(Jan., 1933); C. A. 26:6129; T. S. 97:131.

Various published methods of measuring the smoothness of surfacesare described. Good visual characterization can be obtained by observa-tion.at a magnification of 3 diameters in light coming from one side atan angle of about 4 degrees to the surface. '

556. Brecht, Walter, and Staedel, Wilhelm. Investigation of thesuitability of Belck's smoothness tester for paper. Zellstoff u. Papier11, no. 12:679-686(Doc., 1931); T. S. 94:257.

Data are given to support the following conclusions: A single de-termination with machine-finished paper requires 1 to 2 minutes. Thelimits of error are at the most 2.5%. For reliable results, 10 indivi-dual measurements should be taken at various places on the sample. Thetest should be carried out at a constant moisture content. By means ofthis test, it is possible to distinguish between the wire and felt sideof a. paper sheet.

557. Brush Development Company. Surface analyzer. Rev. Sci.Instruments 12, no. 1:40-41(Jan., 1941). Sec also Brush Tech. Bull.No. 552.

The instrument is designed for making instantaneous and permanentchart records of irregularities in finished surfaces such as metals,paper, etc. It consists of an analyzer head, a calibrating amplifier,and a direct inking oscillograph. The analyzer head consists of thepickup arm and its drive unit; the arm contains a piezoelectric crystalactuated by a sapphire tracer point. The crystal element of the pickuparm has the property of generating a voltage proportional to the verticalnotion of the tracer point as it moves over the surface under test.

558. Clar:, James d'A. Roughness. Proc. Tech. Section, PaperMakers Assoc. Gt. Britain Ireland 8, part l:64(0ct., 1927).

In a discussion of gloss and its relation to roughness, Clark ncn-tions a roughness tester used in Scotland, consisting of an inclinedplane on which the paper was stretched and a wooden block around whichanother piece of the same paper was wrapped. The angle of the plane wasinclined until the block began to slide down, that anglo giving a measureof the roughness of the paper.

59. Davis, Myrl N., and Malstrom, Homer E. Apparatus for testing; the smoothness of paper. U. S. patent 2,050,486(Aug. 11, 1936); T. S.

1041:88.

3^^ ' The apparatus consists of a glass block having a light reflectingbase surface on whicl a paper sheet to be tested is laid, and oppositely

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beveled edges, each at an angle of 45 degrees to the base surface, meansfor pressing the sheet on the base surface, means for projecting a lightbeam normal to one of the beveled edges through the block onto the paper-glass interface, and means for measuring the intensity of the reflectedbeam emerging from the other of the beveled edges. It is possible bythis apparatus to determine the percentage-of the paper surface which is actually in good optical contact rith the glass, and this fraction

.should serve as a measure of the smoothness of the paper surface at thepressure in question. The apparatus described in the patent provides for pressures from 0 to 11,000 pounds per square inch.

560. Dodge, W. G., and Tarvin, E. C. The testing of newsprintfor smoothness, ink penetration, and opacity. Paner Trado J. 100, no. 5:38-40(Jan. 51, 1935); Tech. Assoc. Papers 1:348-350; discussion 60-62Juno, 1935); C. A. 29:3834; B. C. A. 1935B:400; B. I. P. C. 5 :1i6.

In- testing smoothness, two pieces of the same sample are placed uponstool plates which have boon ground to a perfect fit. A mechanism isdescribed whereby a rubbing action is act up between those sheets. Ifthe sheets are smooth, they will slip over each other easily; if they arerough, this slippage will not occur and a weight is changed (positionand magnitude) until an end point is reached. Tho device is calibratedto give rcoadings in units of torque (kg.-cm.) exerted around the axisto which the weighted bar is pivoted. Newsprint gavc readings in therange of 12 to 37 fnits. Tlis instrument gives a good correlationwith the Bold: tooter, but the readings arc samcwhat more reproducible.This is probably because of the larger samples used. In a series ofreadings, the maximamn deviation is about 5%. readingss of about 30indicate that the popor has sufficient. smoothness to take on oven in-presci on in printing, and yoet is not so smooth that difficulties wouldbe encountorod in folding and conveying nochanisms.

561. Fleraing, Herbert. Detormiaing tho smoothness of papor.Wochbl. Papiorfabr. 64, no. 21A:38-41l(iLy 27, 19355); C. A. 27:5971.

A sa!.plc of paper is rotated under a 1-rn. ball fooeeler, the verticalmotion of which actuates a light lever arm. A rider on the arm stands

ft on a smooth plate in suchl a way that it "walks" with the motion of the arm.The distance traveled is a measure of the vertical motion of the feeler

J-' ;. and is reported as rmillimeters per meter length of paper. A second. S reading with a 10-mm. ball corrects for the gross inequalities in the- 2 AA not casac An rouAgnhs1sB.... ,;a n u; _ r W .

suru EtCC not clansed. an roug-noes. ±eaurings con DC UpllaLXuU^u wliilll ,:& , . and inequalities of 0.0003 mm. can be detected.

~ _ 65_02.2 FuCes, R., Inc. The Be;k smoothness and porosity testingapparatus. Instruments 6, no. l:22(Jan., 1933).

...- An illustration and brief description of the apparatus and itsoperation are given.

563. Gurley, W. & L. E. Gurlcy-Hill S-P-S tester. Bulletin No.-' 1490. Fob. 15, 1938. 4 p. Paper Trade J. 106, no. 14:31(April 7,

';i. 1938); B. I. P. C. 8:349.

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Air, at a low,--uniform pressure, is supplied by an -inverted.cylinder, floating frccly in an outside cylinder portly filled withoil. The atr is forced downward, through an open tube, to the upperorifice plato against which the sample is clamped. Each 50 cc. ismarked by rings on the inner cylinder. Thc test consists in timing therings as they dLop past the upper edge of the outer cylinder. In thesmoothness tost, the papor is hold botireaonthe upper crifico plato - --and e lowor platc having a plane annular ring, polished opticsally flat.

- The contact area -is 1 square inch. Light- pressure (3 pounds per squareinch) is provided by an urtweighted lover arm. Eight thicknesses ofpaper are tocsted at one time, which gives an ovcr-all, top-bottomaverage of 16 surfacc areas in one reading. The smoothness value isthe time in second to leak 50 cc. of air (for more rapid work, thcactual reading may be on 25 cc. of air leal;). The paper pad is perforatedby a punch before testing, in order to eliminate the porosity factor.The test may also be carried out with an 8-ply folded sample.

564. Gurloy R. D. smoothness tester. World's Paper Trade Rov. 102,no. 6:4O7-408(Aug. 10, 1934); Paper Trade J. 99, no. 5:20(Aug. 2, 1934);Paper Ind. 16, no. 5:343, 345(Aug., 1934); Instruments 7, no. 8:170(Aug., 1934); Paper-Maker 88, no. 3:194(Sept., 1934); Papior-Ztg. 59,no. 71:1243(Scpt. 5, 1934); B. I. P. C. 5:18.

A description is given of the Gurley No. 4160 R. D. smloothnesstester. It measures the surface porosity or the rate at which air

-,j .flows through the inequalities in the surface' of the paper. A measure-4:W? mont of the time in seconds for a 5-cc. air flow is taken as a rmasure. ~ " of the inequalities of thc sample and indicates the finish."

.56. Helladay, J. F. Printing usc requirements of boxboards.Paper 'ismdc J. 106, no. 25:35-44(Julio 23, 1938); Tech. Aasoc. Papers21:215-224; discussion, 49(Junc, 1938); B. I. P. C. 8:444; C. A. 32:8142.

i .

An appacLratus was constructed for measuring smoothness at increasedpressures. It conistbod of a block of gray iron which was bored andthreaded It rccive the optical flat of tho Bckc tester, drilled withair pasc" 5 s, and connected by copper tubing through a 'rnas adaptor

: . ~to the rorcur;, c-liurm of thc Be!ld tester. Thc block of gray iron| 'g carrying the optical flat is nloced on the platform of the hoovy

Poctory scal, ond centered beneath the screw of an arbor pruss, the, :-. sid_ tension ncnbers of which arc bolted to the main frame of the~. . scale. By the use of this apparatus, it becanome possible to deternine

the approximate smoothnces of samples according to the Bokk prrinciplcbut under pressures up to 400 pounds per square inch. The data covcr-

; inig boards of higher caliper and lower snoothnloss are, for all practicalPl urposes, linear rolationslipsa between smoothness and pressure. OneBSnplc chowed a tendency toward curvilinear trend witlh constantly do-

'[ .croasing slopc. This type of trend is apparent alco on other snmiploshaving a comparativoly high Bckk smoothness. This particular phenomenon

L ~1 was attributable to the increasing affect of lateral porosity. Thesc

' < W data show that onc can cxtrapolatc the trend established by smoothness: {. aObtained at 50 and 100 pounds per square inch and make a closc practical

LiC'- 'extrapolation of the smoothness which is likely to be attained at greaterq " 2 Pressure. Thc ratio of the nsmoothnoss at 100 to that at 50 pounds perL BSquare inch varies from 1.26 to 1.93 forvarious boards.

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- 566; Harrison, V. C . W. -~ The flokk sri:othn6sa -and -porosity tester.Patra J. 1, no. 5:186-192(March, 1953); B. I. P. 6. 8:4437.

Thec Bokk smoothness tes-ter is briefly described, and. its r2Dthod. ofoperation is outlined. The following3 liultetions of thu ins9ti-ment aretainted out:-() It is assumed, that the spaces I ormod betw-ee-n paper

and. glass ope-n into each other so as -todttf continloit -air channel.L;-Although microscopic exaiilnntion shows that this is true in neost causes,itis possible -to- hove a rouGh surface with, a honeycomb or closed --

cellular structure Axiiehohiii have a veryhigh Bek'k smoothiness fi~ure,because the surface provides few opnenpsae from the circunferencoeto the center, cf the rlass ring. (2) -Because of the compressibilitY ofPaper, the snoothnoes changeso rapidly 6ur ingL the first few minutes ofthe application of pressure.- (5) The rate ofI flo)w si air Uhrough atube, other things bo-ing equal, depeInfts upon the four-th power of 'uheradius of the tube. This nears that- the effect' of theo largeOr airchannels is Jct.rweighted, at the. expe,,nse of the simller, and. asurface whicli p-rovides a few large and mnany er-a11 cIlornels may appearto be rougher thrmn actnIal2.y -is the cane. Thus - U'' instrument foilsto rtiffc-rcnrtiatu beo.ween. a svrfL'aee on. which tho ia'glrtc rclarge but comparatively, few, and. one on which thoey Qgo small butnumerous.

567. Heingo, M4., and. Baiid., P. K.. - A method for evaluating -thesurface roughness of paper. Pa-per Trade J. 113 no.- 15:31'-56(oct. 9,1941); Tech. Assoc. Papeors 25:619-624(June.,, 1942); Paper LInd. 23, no.8:83o-832(Nov., 1,941); B. T. P. C.- 12:81; C. A. 35:8292.

The roughness tester is based upon t~he prircin~le of direct deter"-nination, by chnnical neane of the deviations Cram1. a fixed plane ofthe paper surface~ at a series of" points. K1.though it emaploys the tracerprinciple, it diifei'-s in. thant the detector needle rvekos contact bymeans of an ixiterti-ttiont vortical. intl-an which elirminates the objection-ab)lo side stresses oant plowing- offset of c"ontinnous tracinG. The paperto be tested is held by a damnx consisting of an fixed. upper contactniece and n Ymovablec lower ca ta t iec e. M e uppr), pic e fins a 0.254-nixl. Eianetor hrle th-rouh w~hcich the detector eed~le imaes contact viththe paper surface. This neodl.e consists _f' al stea-l stylus, the pointof which is jreunE to a- truncated cone havi-ng a fis~t end. 0.053~ Lm.(0.0015 inch) in dliameiter; an lo ofi approx-trntel::, 0.05 gram is en-ployed on the eele About 500 rcandLtyrs are tak':,, onl one sampqle.tione the factors investigated, were the'arspei conditions and.

.- mechanical disturban)ces, ciraning p)ressure, diameter of the r!etector-needle h-.hale prosscure of the deotector needles, diame10ter of the needle

~7{'point, and r? -Thor of rcadings;F p)-r sample. Values are given, for a--- number of typi:cal -papers. Thec stand.-ard deviatilon of 'the readings is

)--Gles influenced by th; Cer-r-r oif :ensuror.'.en' Lhan the0 arithmeotic aver-age. A curve. i½ vhich Inrgecrsoli glecs is n~td against roughness,Choh ws the. inadequacy of tho ls esrmn to) evaluate roughness.

2GImatli §~. -Instituite of Parecr Chemistry. ITnsatrm. xntatin studiesu. IX.

The Bflek anti Gurley soriuthnesu te-sters. Popur Trade.c J. _104, n-a. 12:62-66(March 25,. 1957); 13. I. P. 0. '(:279; F. C. Al. 1{95713:657; C. A. 31:4813; T. 3. 106:50.

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Smoothness 204',

A description is given of the two testers, and a discussion is;' presented of the theory of the Bckk tester. From the data for a large

"i number of papers, it is concluded that the two testers do not measurethe same properties of a paper shoot. The results lead. to the suspicionthat the Bokk readings are influenced by transverse porosity and togreater extent than .in the case of the GurIcy instrument. The-Bckk readings, which are high in comparison with the Gurlcy readings on the

----- same-samples, roe -taken on papers having a relatively high porosity.. If a correlation exists between the two instruments, the difference

in the effect of transverse porosity could logically be accounted forby the design of the instrument, because the air pressure at a givenrate of air flow is higher in the Beld than in the Gurley tester.

569. Institute of Paper Chemistry. Instrumentation studies.VIII. An analysis of smoothness. Paper Trade J. 104, no. 11:43-46(March 18, 1937); B. I. P. C. 7:279; B. C. A. 1937B:427; C. A. 31:4813;Tech. Bull. 14, no. 5:57-58; T. S. 106:50.

This article is devoted principally to a discussion of the smoothnesscharacteristics of printing paper under the hoadit:ga: typical surfacedefects of uncoated papers; surface defects due to tho coating process;surface defects due to both the uncoated sheet and the coating. Mentionis made of a device for making a single measurement on a large area ofpaper. For this purpose, a separate panel and attachment were builtto be used on a brightness tester. The sample could be rotated through180 degrees about on axis at 22.5 degrees to the fixed direction of theincident Jight bean. The possibilities of the method were not thoroughly

:[I *investigated.

570. Institute of Paper Chemistry. Instrumentation studies.X. A discussion of methods for measuring smoothness of paper, withspecial reference to a new electrical capacitance method. Paper Trade J.104, no. 13:30-33(April 1, 1937); correction, 105, no. l:127(July 1,1937); B. I. . C. 7:314; B. . A. 1937B:657; C. A. 31:4813.

Under methods for measuring the smoothness of a free surface, thereare considered the following methods: direct measurement of the surfacecontour by means of a microscope with micrometer focusing adjustment;direct measurement by means of a small "rider" under which the papersurface is caused to move; electrical "pick-up" method; friction methods;

" |: methods utilizing oblique illumination; and electrical capacitancemethod. The second section considers methods for measuring the smooth-

~ ; - ness of a compressed surface, which include the method of air resistance* -- (the basic principle of the Beldc, Gurley, and Williams testers)' and. : the Davis smoothness tester. The promise and limitations of each method

are considorod briefly. Details are given of preliminary work on theelectrical capacitance method, in which the electrical capacitance is

" ~i measured of a system consisting of two brass plates separated by a sheet0'.. of paper and of a system in which one of the brass plates is replaced

'^' by a liquid mercry.. surface. The results were compared with Bckk' .a.. and Gurley tests; no correlation existed between any one of the three

g- R sets of instrumental data and visual grading. The investigation of theDavis tester showed that the instrument does not grade coated papers in

1

Smoothness 205I;.

agreement with the visual grading and that, taicing formation into account,the irstrumrnt seems to give a reasonably good nmasuro of printing smooth-ness on finished coated paperc. A variation in tho tester is suggested, inwhich tho face of the glass prison is covered with a thin, uniform film

..|. .. of clear oil; lwithithis modificat'.on, thc area of optical contact, withincreasing pressure, would incrcaco at a rate depending on smoothinoasand corprcssi'ility and the thiclc;ess of the oil filn. It is apparentthat the prcsauro-requirod for-noarly the whole of the available surface to cone into optical contact would bo reasonably low.

571. Institute of Paper Chemistry. Instrumentation studies. XXV.The Williams srioothnoss tester. Paper Trade J. 106, no. 4:38-42(Jan. 27,1938); T. S. 106:325; B. C. A. 1938B:499; B. I. P. C. 8:252; C. A. 32:2745.

The Williams smoothness taster provides for measuring a constantvolumo of air, which is compressed and applied to the conter of a cloapholding a folded-ovor sample of paper under definite pressure, in such- way that the air can pass bctwoon the .two urfaces of the paper. Theresults nay be corrected for the transvorso passage of air through thesheet structure (transverse or plane porosity); provisions arc made forthis neasuroment. The various units of the instrument were studied,including the air measuring cylinder, the timing mechanism, the clampingdevice, the calibration standard, the measurement of the transverseporosity, anrd the reprodcucibility of the results. A comparison is alsogiven of thc results from the Williams and the Bock smoothness testers.It is concluded that transverse porosity accounts for all or practicallyall of the air escape when smoothness readings are mado on coated

!. '^' samples of hi,,h smoothness. As a corollary to this, it rust be con-eluded that, in the case of very soooth papers, smoothness readingsmade on this typc of inatruncnt are principally a measure of transversoporosity rather than a nmosiaro cf smootihnloss. Also, it is doubtful ifthe fornmlle used for calculotirg the ocrroctcd :.aootlmrosc is applicable -under those conditions. Fro these results it would seemon that all in-strur.onto based on this princinlo are influenced to an appreciable

"^*t'- Oxtont by transverse porosity. Thec results given here cast some doubtupon the valuo of those instru^cnts for uce with very smooth coatedpapers and. indicate the necessity of applying the transverse porosity

A '.. correction to all. tests. When factors affecting transverse. porosity,;. ' such as thiclmoss, apparent density, and furnish are considered, it is

; K- °:' apparent that transvcrse porosity can vary widelyy without a necessary4',i,,. '[ variation in smoothness and if the uncorrocted smoothness reading,¶ '&.:Kf."' which is a measure of both smoothness and porosity, wcre used,

erroneous conclusions might be drawn. The W'i'lians tester rnasurcsi ~ ,^^ ij! ' a similar quality to that measured by the Beld: inostrlnint but differences

'" g~ . do exist and the two testers do not omasuro exactly the same quality.·. i i.. It should be said at this point that whatovor lack of correlation is

y:.., shown in thus results is not a criticism of either instrument. Ast pointed out before nonc of the instruments basuod on this typo of

test con nmasurc a single fund:aicntal property. Rather, the resultsO6 are affoctcd by several conditions; therefore, the value of any in-O -strument lies in its ability to ovaluato a paper for a specific use

;. requirement.

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Smoothness 206

572. Institute of Paper Chemistry. Instrumentation studies.CXXXVI. The Gurley-Hill S-P-S tester. Paper Trade J. 110, no. 23:27-33

(June 6, 1940); B. I. P. C. 10:429; C. A. 34:6067; B. C. P. A. 1940B:662.

The Gurley-Hill S-P-S tester was designed to measure the softness_.(or compressibility)/-,dr6osity, and smoothness of -paper. In each case,

the measurement consists of observing the rate of air leakage over or-- through the paper specimen.. Uniform air pressure is supplied by means

of an inverted hollow piston floating freely in a cylinder partly filledwith oil. 'The air is forced downward, through an open central tube, tothe upper orifice plate against which the sample is clamped. Interchangeablelower test plates provide for measuring softness, porosity, or smoothness.Uniform clamping pressure is provided by means of a lever; one endsupports the lower plate and other end supports weights calibrated togive the desired pressure on the paper. The rate of air leakage overor through the specimen, depending upon the property being measured, isdetermined by timing the movement of the graduations on the piston oasthey pass the upper edge of the outer cylinder. Except for the inter-changeable lower plates and the lever arm, the instrument is similarto the Gurloy Improved Densometor. In the Gurloy-Hill S-P-S rapidsmoothness test, eight thicknesses of paper are perforated and hold be-tween the upper orifice plate and a solid lower plate having a planeannular ring, stated to be optically flat. The test does not differen-tiate between felt and wire side smoothness but gives an average valuefor sixteen surfaces. By means of the lever arm, unweighted, a pressureof 3 pounds per square inch is provided over a contact area of 1 squareinch. The smoothness value is defined as the time in seconds for 50 cc.of air to pass. For rapid routine control testing of smoothness, asingle sheet may be folded 8-ply. The pad thus formed is perforatedand tested without unfolding. For more accurate work, eight separateplies should be tested. The following aspects of the smoothness procedurewere investigated: (1) Proportionality of observed time to volume ofair flow; (2) proportionality of observed time to number of plies usedin each obsorvation;'(3) effect of orientation of wire and felt sidesof adjacent plies; and (4) effect of grain orientation in adjacent plies.The observed tine in this test was directly proportional to the volumeof air flow and inversely proportional to the number of plies tested atone time. The results correlate fairly well with Bekk readings butvery poorly with Gurley R. D. smoothness values. For papers withinthe 'ordinary range of smoothness, the testing of 8 plies simultaneouslyyields an average and reproducible instrumental reading. For very smoothpapers, the nuzmber of specimens tested at one tine may be increased to

4 t- twelve or purhnps oven sixteen and the volume of air flow reduced to 25 cc.The results thus obtained can be refeorroed with small error to standard

.'"' conditions. However, for accurate work, conversion factors should be dc-,] t'. termincd for each closs of pcpor. Orientation of both the sides and

/4 ,' direction of grain of adjacont specimens tooted simultaneously apparentlyhad no affect on the smoothness values obtained. In grouping a number

jj ~ . ± of specimens to be tested simultaneously, precaution should be taken to:, \iY arrange concentrically the punched porforatlorn in the sheets. The

Gurley-Hill S-P-S tcostr nooasured in a reproducible manner certain proper-4 ? V,, ties of napor si-ilar to those measured by the Bokk omoothnces tester and

the Gurley densonoter. However, poor correlation was found between

Smoothness 207

S-P-S softness and Federal compressibility and between S-P-S smoothnessand Gurloy-R. D. smoothness.

57'I. Jones, Charles H. LoP. Paper-finish tester. U. S. patent1,668,593(maY 8, 1928); Paper Tlede J. 88, no. 4-:50(Jan. 24, 1929);Zollstoff Tu.-Pnicor 9,- no. 5:294(4May, -1929.).

With this apparatus, a numerical indication can be obtained ofthe relative smoothness of any numteCr of snIpplos and compared with theIndication obtained from a satisfactory sample adopted ns standard; theoperator can. detorrrino with great accuracy whether the finish of thesample is above or below standard and to what degree. The principle ofthe instrument consists in placing a shooeet of the paper on a smoothplano surface, causing a smooth-faced drag to be moved over the surfaceof the paper by the action of a predetecrr.inod force (such ns gravity),and obtaining; an indication of the mcan rate of movement. Preferably,the drag is always moved th-rou3h a fixed distance, and the indicationis of the tine occupied by the drug in traveling that distance. Inpractice, it has been found that best results are obtained if the tableis sot at an crgie of boat 27 degrocs to the horizontal and if theweight overbalances the draes in the ratio of about 10:9.

574. Kantrowitz, M. S., and Sinmons, R: H. Evalunting the printingqualifications of paper. Paper 'Trnalo J. 105, no. l:97-102(July 1, 1937);Paper Mill 60, no. 27:13, 15, 18-21(July 3, 1937); B. I. P. C. 7:434;B. C. A. 1937B:894.

Smoothness is one of the most important properties of paper fromthe standpoint .of printing. Brief reference is made to the Bclck,Gurlcy, and Williams testers, and a proposed TAPPI standard is out-lined for the BckXk test of the rclotive printing smoothness of paper.

575. Kott, Hermann. Surfaco smoothross tostcr. U. S. patent2,251,613(Aug. 5, 1941); Papermaking Austr. 1:195; C. A. 35:7194.

Tro beams of substantially identical intensity are directed froma constant source of light upon the opposite faces of the sample tobe tested, and the li3ht reflected from the surfaces is then directedto a photoelectric call. The twon light besrn originating from thesource are alternately interrupted in such a fashion that the raysfalling on the photoelectric cell from each bcan vary sinusoidallywith time and arc 180 dCegees out of phase, so that equal areas ofthe photocell are illuiinatod nltornatcly. One side of the surfaceto be tested is sErndgcd wit-h ink so that it appears darker thlmn theclean surface, the degree of dsar:cning dcoending directly upon itssmoothnesss. The light now reflected from the sznudgcd surface is con-siderably less than. that reflected from the clean surface, thus pro-ducing an alternating current in the circuit of the photocell. Thealternating current is amplified in. a specially balanced amplifieruntil it is of sufficient magnitudc to operate an indicating metor.The bean of light which .is directed on the clean side of the testsurface is now reduced in area by reano; of an -iris diaphrau- untilthe reading of th indic tin, t rought -to zero, at which point

1&

Snoothness

the beams of light reflected from'tho smudged surface -and the clean -surface are equal. The relative smoothness of the surface may then beread directly from the iris diaphragm, which may be suitably calibratedto read percentage smoothness.

576. ILnrocque, G. L. The control of printing quality in the paperand board mill. Paper Trade J. 106, no. 26:86-90(June 30,1938); -''Paper Mill 61, no. 29:17-18, 20, 22, 24(July 16, 1938); Paper Ind. 20,ro;.4:46o(-July; 1938); Am.-Pulp Paper-Mill Supts. Assoc.,--Year-Bookand Prograr 1938:236-240; discussion, 240-242; B. I. P. C. 8:490; C. A.32:8141; B. C. A. 1938B:1026.

This article contains a brief review of the measurement of printingomoothnecs, with reference to the work of The Institute of Paper Chemistry,Halladay, and that of the author.

577. Mastcn, Ralph A. Smoothness tester. U. S. patent 2,019,541(Nov. 5, 1935); T. S. 103:191.

The invention provides an instrument for measuring the smoothnessof paper by determining the time required for a known quantity of airunder known pressure to escape between a smooth true plane of standarddimensions and a sample piece. It permits the determination of thisproperty for each side of the a sam e separately and simultaneously.

578. Paper testing device. Ind. della carte, Jan. 31, 1924;T. S. 79:147.

tAn apparatus for measuring the surface smoothness of paper isbased on thi resistance it offers to the movement of a point--that is,on the basis of the attrition which develops when a point traversesthe sheet under constant conditions. The device consists of a pendulumcarrying a pen which touches the sheet as in writing. The sheet isplaced upon a horizontal plane with a to-and-fro motion. The oscilla-tions of the pendulum are proportional to the smoothness of the paper.

579. Prior, Philip H. Experiments in printing. World's PaperTrade Rev. 102, no. 25:1874, 1876, 1879-1880, 1882, 1913; no. 26:1944,1947-1948, 1950, 1952, 1954(Dec. 21, 28, 1934); 103, no. 1:60, 62(Jan. 4, 1955); discussion, Tech. Convention No.: 68, 70, 73-74, 76-78(March, 1935); Papor-Maker 90, no. 4:TS155-160; no. 5:TS1l4-166(Oct.,Nov., .935); Pnper Trade J. 101, no. 15:39-44(0ct. 10, 1935); Proc.Tech. Section, Paper Makers' Assoc. Gt. Britain Ireland 15, part 2:335-354; discussion, 355-364(March, 1935); B. I. P. C. 5:159.

An appendix (page 354 of the Proceedings) describes an apparatusfor viewing the surface of paper which is under pressure. A glass plateis held by Jaws, which arc shaped to allow a microscope objective toapproach, while giving the maximiu possible support to the glass. Thesample is pressed againat.the-glass by a plunger, spring, and screw. Thepressure can be determined from the compression of the spring; thus farit has booen possible to attain a pressure of 100 pounds per square .inch.If an intense and narrow boea of light is projected on the end of the glass

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Smoothness 209

in. a direction normal to the plane of the diagram, the points Of contactbetween thep paper and. glass appear bright against a dark backg'otuied.

580. flondall, A. G. Paper testing. Proc.. Tech. Section, Paper-nker U4so . -Bti~tcin Iroland5", part 2:l36(Ma1reh, -1925). -- -.

-- The. method suggesoted for ~the slip pi' paper is the same as thatrQtTofl by Clark, (Nol. 558").

58~1. 1Rouglhr.os tlester. Patra J. 3, no. 2:76-77(So-Pt., 1939).

This instrument (developed in theo Scarutinovian lhboratorIos) is amodification of thea Iokk- smoothness toter. 'Bic principle is the sane,in tha t -the speed. at which air ~s nade to fl'Iow across the paper surfaceis a measure of the roughness of the surface but, instead of causing theair' to flow between the, rough paper~ surface and. a smooth glass rina: ofconsiderable area, the now instrument uses a narrow ring~, the breadthof which is less than, the cavities which are likely to be present -in.the surface of the papor. In. order to minimize the errors resulting fromthe porosity of the paper, the pressure used to drive the air acrossthe1 paper i's reduced to a constant value of about :t5 cm. of water endthre rate at which it £lows is measured by means of a rotameter. Thleroughness of the paper. surface is measured, by 'placing the r,)per to betested en a smooth Class plate as a support. rThe tester is placed on

top, and the nosition of the cone in the rotameter column gives annnnodliate reaffinj of th's roughness. By increosirj, the pressure on) thetester, the eff.-ct of the compressibility of the paper can be studied.A-n additional appliance also enables the tnntrur~ont to be used forroronity::, rnasvremriotp.

p8.Simzons, R. H. Paper quality in. relatiror to printing., PaperThande J. 109, no. 19:37-4i0(Nov. 9, 1939); Tech. Aosse. Porror 22, t-o. 1:469-473; discussion, .119-121(Juno, 1939); B. I. P. C. 10:129.

The sirgnificnrco of nnoothncsc in printing~ papers is discus,-rce.Pzogthe wzntlxofs listed are the Bekk smloothness testtr, the WiJliansi

smoo0thness and. r~nen. norocity tester and the CvrJley sueothness tester;the last has,, been eiie to nyrecuce the Gurcy-Y-Hill softnesis tester,

rhich is nce adcmted.c to make smooth Uness tests; mcntlon is maode alsoif he TLevijs ro thod. These methods all give relative readings f or

speoliocbiTht because, of variations in the nressures and, methodsG ofmerasuring, the n7iznerical read~rnGs oI' one are. not directly con~vertiblei-nto any other.

58.Underhay, G. F. The BcIr,:400ot1Lmess and p~oros:tty tes~ter.World's pajnur rrnaoeBoy. 101, no. i1-3:11d4$,lFFOia, 1954); PprMnker 87, no. 5: 1428-429(M4ay, i1954).

A brief description Is given of the apparatus, and! comoroarativofigures are reported for the Deirk s1moiothnessj and the) Thg-crsoil glossfor three types 01 newsprint.

Smoothness 210

584. Wehmhoff, B. L., Simmons, R. H., and Boyce, D. H. The Bekksmoothness tester as an aid in studying the printing quality of paper.Paper Trade J. 96, no. 4 :36-40i(Jan. 26, 1933); Tech. Assoc. Papers 16:'.264-268(June;-1933);--C;-A--27-:2808; T. S. 97:222;-B. C. A. 1933B:263;B. I. PC. 3:145.

A brief description of the tester is'given; From a series of-tests,the experimental error was assumed to be 9.5. FvnPrt-ltFn+ it+h m+nt-ri-als other than ruJbbor (vinylite resin in acetone, tinfoil and acetone,lacquer and cellophane) showed that the use of any adhesive or means ofinsulation other than soft gum rubber entails useless labor and detractsfrom, rather than adds to, the accuracy of the tests. The results at65% relative humidity are approximately 10% lower than those at 50prelative humidity. Tests on some 300 samBplo of commrcial newsprintgave average smoothness values of 43 seconds on the felt side and 51seconds on the wire side. Smoothnosc increases regularly with the amountof calondering. A comparison of newsprin)t from 5 mills showed a varia-tion from 47 to 92 seconds for the wire side and 41 to 108 secondsfor the felt side; similar variations in smoothness were found for samplesfrom the sane mill. rNo definite relationship could be established be-tween the anoothncss and rate of oil absorption of newsprint and mimeo-graph papers.

585. Williams, 'Frank M. A new electric finish, formation, andplanoradial porosity tester. Paper Trade J. 98, no. 15:41-43(April 12,1934); Tech. Assoc. Papers 17:286-288; discussion, 70-72(June, 1934);Paper Ind. 16, no. l:46-47(April, 1934); C. A. 28:3898; B. C. A. 1954B:474; T. S. 99:94; B. I. P. C. 4:218.

A uniform air supply is provided by neans of a definitely weightedcylinder, closed at the upper end but open at the bottom, which is al-lowed to fall a definite distance into a mercury reservoir that acts asa seal to the lower end of the compression column. Tho end point of thetest is accurately and automatically determined by means of a plungerrod attached to the falling cylinder which makes an electrical contact,closing the circuit of an eloctromagnet which is connected through aspring and pull rod to a stop watch. Uniform clamping pressure is so-cured by c screw clonp rith a diaphragm hydraulic press foot, and theexact pressure is accurately indicated upon a gage. Holes or perfora-tions in the center of the folded sample or of the sheets allow freeaccess of air to the space between the two surfaces which are undertest. Tho nothod of operation is described. The accuracy of the testis doubled by having two surfaces of paper in contact. Plano-radialporosity io tih tine required to force a definite quantity of air,under standard prcscureo conditions, a fixed distance through the actualpores or tc:-:ture io the sample in the sane plane as that of the sample.After the firil!ch of both sides of a' paper has been determined, a per-forated pieco of rubber is inserted between the folded surfaces ofthe sample anrd the clampingo pressure brought to standard conditions.A reacurcd quantity-of air at a definite pressure is forced out throughthe presc or fleo' in the anme plane as the sample to a distance equalto 0.5 inch.

I

Smoothness

586. Williams, Frank M. The relation of smoothness and planeporosity to printing qualities of paper. Paper Trade J. 100, no. 23:37-39(Juno 6, 1935); Tech. Assoc. Papers 18:437-439(Juno, 1935); C. A. 29:5268;B. C. A. 1935B:719; B. I. P. C. 5:308.

The snoothncos of a sample of paper is dotoriiied by measuring thetime (in seconds) required for a definite amount of air at a definitepressure to bo-forced between-two surfaces of-tho sample folded upon.it-self, perforated in the center, and clamped between rubber-faced plateswhich seal the two outside surfaces of the folded sample against anyescape of air. The compressed air supply is obtained by a weightedcylinder, open at the bottom end, and descending into a reservoir ofrmrcury. The sample under test is clarpod at a definite pressure, asindicated upon an accurate pressure gage. To make a test, it is onlynecessary to raise the central colunn to a given height and latch it.The soaple is inserted and clamped to the desired pressure; a lover un-latches the falling column, and the tino is indicated by a stop watchor Telochron clock. Various experimental data are given.

587. Williams, Frank M. Studios upon smoothness, porosity, andprintability of paper rith new methods for determination. Tech. Assoc.Papers 20:305-309(Juno, 1937); Paper Trado J. 105, no. 8:43-47(Aug. 19,1937); B. I. P. C. 8:34; T. S. 106:92; C. A. 31:8188; B. C. A. 1937B:1189.

The Willianm tester consists of a base in which a vertical outsidecylinder is inscrtod. Inside and concentric with this is a 1/0-inch pipereaching practically to the top of the outside cylinder, which is connectedwith the sanple claom and furnishes a rnans of conducting the compressedair to the sapnlo. Tlo annular space boteeon the 1/8-inch pipe and thelargo outside cylinder forms a rmrcury reservoir. A thin, movablecylinder, open at thu'bottom, is inserted in this annular space. Theoperation cf the instrument is described, as well as the method ofmaking a test. BaroLmtric pressure, as well as the temperature andhumidity conditions, is an important function of all smoothness testersof the air-flow type. Standard permanent test plates should be availablefor chocking any smoothness testing instrunent. In specifying a definitecomprcsuion area, both the inside and outside diameters of the limit-ing circles should be given. By using square. clamping plates, omothnessand plane porosity tests nay be made upon a sample with an air flow ofequal velocity over the entire surface of the sample tested. It ispossible, by moans of square test plates, to make smoothness and planoporosity tests both in the machine direction and across the sample.The reading upon the Williams instrument may be correlated with those ofthe Bcldc instrument when those are taken under carefully controlled condi-tions.

588. Williams Appcratus Co. Paper smoothness and formationtester. Inotrumont;7, no. 10:218(0ct., 1954).

A brief description is given of the Williams electric smoothnessand for:n.tion tester. Ar illustration is included.

589. Zipkin, G. S. Bckk's apparatus for the determination of thesmoothness and porosity of paper. Bumazhnaya Prom. 15, no. 3;49-52(March,1936).I.

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Stiffness, Softness, Rigidity 213

The apparatus is similar to that used for measuring compressibilityby a dynamic load (see Compressibility). The height of the rebound isroad on a scalo fitted attlio side and thoolostici-y of tihe paper isexpressed as the percentage which this value represents compared withthe.hoeighit of rebound obtained .from the- uncovered steel- support. Anapparatus is also shown for measuring the resistance of paper to bend-in; stresses within the elastic limit. The sample piece is arrangedso that it forms a semicircular arc of 10 cm. diameter, provided noflattening is produced under the influence of its own weight. The wholearrangement is placed upon the pan of a balance which is adjusted to theequilibrium position; a plate of glass is placed above the arrangementin such a way that its lower surface, when the balance is adJusted, isexactly it cm. above the baseplate holding the paper. The weights necessaryto be added to the balance to produce equilibrium in this position ropro-sent the force necessary to press down the semicircular strip by a dis-tance of 1 cm.; when the value is calculated for a strip cmn. wide, itrepresents the resistance to bending or the stiffness of the paper.

~~. lBorrdt, Kurt. Recent laboratory instruments for the pulp andpaper industry;. Zollstoff u. Papier 17, no. 7:309-312, 314; no. 8:349-352(July, Aug., 1937); B. I. P.- C. 8:74; C. A. 31:8188; B. C. A. 1937B:1321.

A description of the Zander stiffness tester is included.

24k. Berndt, Kurt. Stiffness testing of papers and boards. Papler-Fabr. 33, no. 48:393-393(Dec. 1, 1935); B. I. P. c. 6:245.

An apRaratus is described and illustrated for measuring the stiffnessof paper and boards. The force necessary to bend a strip of definitewidth and length through a measurable arc is determined.

29. Bragg, A. O. Stiffness tester for boards. Paper Makers'Mo. J. 63, no. 2:49(Feb. 15, 1925); Paper 35, no. 5:177-182(Nov. 20,1924).

96. Brecht, W., and Blikotndt, F. A new instrument for testingthe stiffness of papers and boards. Papier-Fabr. 38, no. 4:17-22(Jan. 26,1940); Ind. carts 7, no. l:15(Jan., 1940); B. I. P. C. 10:300.

A new instrument has been devoloneod for measuring the bending stiff-'neas of paper and board. One end of the sample strip to be tested isfixed to a cylinder so that it follows the curve of the cylinder for acertain distance, a weight being attached to the other end of the strip.The force required to revolve the cylinder is taken as a basis of themeasurement. Strictly, for each paper thickness a certain cylinderdiameter should bc used; because this is not practical, a scrics ofcylinders are used, the diameters of which form a Coometrical sequence.The best relation of the weight in grams to the cylinder radius in mm.was found to bo 4.5. The theory of the measurement is discussed. Theoppllcation m, the bonding test method to thc d.tcermination o'f ulauticityis described.

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597. Brecht, W., and Blikstadt, F. Testing the stiffness of paperand boards. Papier-Fabr. 36, no. 4 9:532-538(Dec.- 2, 1938); B. I. P. C.10:21.

After a theoretical discussion of the resistance to bending andelasticity in general, bending formulas for paper, cardboard and similar

- -- terials are derived.--17 references.--- -

98. Brown, T. M. A method for determining softness of soft papers.Paper Mill 52, no. 23:19-21(June 10, 1939); B. I. P. C. 9:515; B. C. P. A.1939B:1029; C. A. 33:c635; Tech. Bull. 16:115-116.

A description is given of the Brown Company paper softness tester,which measure the force necessary to crumple a wad of the specimeninto a definite volume; hence, it is different in principle front theusual commercial stiffness testers. It has the great advantage of beingvery inexpensive and can be built from ordinary laboratory equipmentat a coat of less than $5.00. It is sufficiently reliable on the typesof paper where softness is an important factor, such as napkin stock,facial tissue, lightweight toweling and similar stocks.

599. Carson, Frederick T., and Worthington, Vernon. Evaluatingthe wearing quality of currency paper. J. Research Natl. Bur. Standards26, no. 6:467-480(June, 1941)(R. P. 1390); B. I. P. C. 11:417; C. A. 35:6108.

A stiffness tester is described for use with crumpled paper. Be-cause the results did not give the necessary information for the problemin hand, the apparatus was not completely developed, although there wereindications that a very sensitive and significant asooure of planeshoots night be obtained by further dcvclop:ont of the instrument.

6O0. Carter, E. .The Carter paper stiff ncs tester. PaperTrade J. 93, no. 15:54(0ct. 8, 1931); C. A. 25:5987; T. S. 93:276;B. I. P. C. 2:135.

An apparatus is illustrated and briefly described. The stiffnessis taken as the load in granm required to bond a sample through an angleof 90 degrees.

601. Clark, James d'A. Determining the rigidity, stiffness andsoftness of paper. Paper Trade J. 100, no. 13:41-44(March 28, 1935);Tech. Assoc. Papers .8, no. 1:234-237; discussion, 62-65(Jurn, 1935);C. A. 29:3832; B. C. A. 1935B:490; T. S. 101:510; B. I. P. C. 5:249.

A review is given of the types of stiffness testers under theheadings: cantilever, bean, column, folding, modified cantilever andpendulum. A new method is proposed, which is now the basis of theTAPPI method.

602. Dantzig, Tobias, and Peterson, Esther C. Apparatus for measur-ing the stiffness of flexible materials. U. S. patent 1,824,395(Sept. 22,1931); T. S. 94:280.

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Two flexible rolls are mounted near the upper edge of and verticallyto a vertical board, which supports an inclined straight guide, thelongitudibnal' xi s - o f - w h ich passes thrbough-the liTnoeof-contact of the rolls.Thu end of a test strip of convenient length and width is engaged be-tween the rolls.and the latter are slowly turned until-the free end-of the test strip barely touches the guide. The stiffness number ofthe material (defined as a number proportional to the cube root of theelastic moduli) is read off directly on a scale marked on the guide.

603. Davis, D. S. Nomographs for rigidity, stiffness and softnessof paper. Paper Ind. 17, no. 6:409(Sept., 1935); T. S. 103:85; B. I. P. C.6:146.

Two charts are given, one which permits the computation of rigidity,stiffness, and softness, and the other of the rigidity factor.

604. Elald, W. New stiffness tester for paper. Papicr-Fabr. 25,no. 20:301-502(May 15, 1927); Zcllstoff u. Papicr 7, no. 3:112-115(March, 1927).

Illustrations are given of the stiffness tester used by Schulz andEwald [No. 626]. Data are given for strips from 5 to 13 cm. in length.The effect of length is not as great as previously assumed.

605. Fuocs, R., Inc. Paper testing instruments make possible newtests. [Smoothness, fuzz and stiffness testers]. Instruments 6, no. 1:22(Jan., 1935).

Diagracs and description of the stiffness tester.

506. Gurlcy, R. D. Stiffness tester. Paper Trade J. 99, no. 25:43(Dcc. 20, 1934); Paper Ind. 16, no. 8:573(April, 1935); Instruments8, no. l:22(Jan., 19355); soo also Gurley Bulletin No. 1420(Feb. 1, 1935);B. I. P. C. 5:129.

The [tiffncss of the paper is measured by clamping a prepared samplein a movable arm and drawing the paper over the top of a weightedpointer until the bending of the paper releases the pointer. The amountof deflection of the pointer, road on a scale at the bottom, is the measureof stiffness. The clamp holding the sample can be raised or lowered onthe am, permitting the use of samples from 1 to 4.5 inches in length.The pointer can be loaded with weights of 5, 25, or 50 grams, placed atany one o' three distances below the pointer. The clamp arm is rotatedby n wire bolt running from a capstan handle, which is turned in order tomove the papcr. The operation of the instrument is described.

607. Institute of Paper Chemistry. Instrumentation studies XIV.A comparison of the Smith-Tabor and the Gurloy stiffness testers. PaperTrade J. 104, no. 21:43-47(Mny 27, 1957); B. I. P. C. 7:390; B. C. A.1937B:770; C. A. 31:6877; T. S. 1056:93.

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The reading of the Gurley instrument is highly dependent upon thenature of the cdge of the paper sample and the smoothness of the surface.An apparent increase in stiffness is produced by any friction betweenvane and paper. The effect of the edge and surface of the sample isclininatEd in the Cartcr' although the-length and width should be ac- -curatoly established. The Gurley is very sensitive to length of sample.The angle of bond. being larger in-.th Carter tester, thc force requiredis correspondingly larger and thus more accurately measurable. However,the disadvantage duo to the deformation of the paper is objectionable.It would be instructive to build a Carter tester using an anglo ofbond comparable to that of the Gurloy. If an accuracy in the determina-tion of this bend comparable to that obtained by the nethod employed inthe Gurley tester could be secured, the advantage of the static readingof the Carter would be obtained without the disadvantages of either in-struront. The zero of the Carter instruwont is not as dependable as de-sired. Any friction in the bearings is objectionable in establishingthe zero. As the curves indicate, however, stiffness as measured by theCarter tester is closely comparable to that as measured by the Gurley.The'curves arc very nearly straight lines, and the experimental pointsfit the curves very closely. The Gurley tester is useful over a widowrange of papors, but for light papers the Carter is very convenient,readings bcin:; obtained in a shorter time than with the Gurley. Theweight of the paper would tend to lower the value of stiffness asmeasured on the Carter while increasing the value as measured by theGurley. This is a possible explanation of the fact that the curves donot tend to pass through the origin. For papers whose stiffness is veryhigh, the Carter instrument is unsuited, because of the uncertaintyin the force to produce 90-degrec bonding, this force varying with time.For such papers the Gurley tester is to be preferred. All papers wereranked in the sane order by both instruments, and any departure fromthe curves arc within the experimental error.

609. Institute of Paper Chemistry. Instrumentation studiesXXXV. The Clark paper softness tester, with an important note on theGurley stiffneos tester. Paper Trade J. 110, no. 7:29-37(Feb. 15, 1940);B. C. P. A. 1940B:351; B. I. P. C. 10:249; C. A. 34:5085.

The operating technique for tho Clark paper softness tester hasbeen studied in rsoe detail. The overhanging length of the paper stripinserted in the roller mechanism of the instrument has been found tobear a straight-line relationship to the angle of rotation necessaryto cause the strip to fall over. The correlation between Clark rigidityand Gurley stiffness was poor for limp paper but somewhat better for

.-' ^ stiff paper. One of the principal reasons for this poor correlationwasoo found in the large source of error in the Gurley method, whereinerrors range up to about 90% of the apparent Gurloy stiffness. Clarkrigidity was found to correlate well with flexural rigidity as determinedby a research method involving a torsion pendulum.. Subjective testsfor softness of facial tissue, towel tissue, waxing glossine and broadwrappers correlate with th neoan of the machine direction and the crossdirection Clark softness values. The accuracy of determinations carriedout on the Clark paper softness tester depends largely on the nature ofthe paper tested. For heavy, uniform papers, five' determinations in

,- ' each direction ore sufficient, but at least ten representative strips in!: ^.,' each direction are necessary for lightweight papers.

I

.. . -Stiffness, Softness, Rigidity 218

610. Isnard, Raymond. The testing of cardboard. Elasticity orrigidity and folding. Papeterie 43, no. 11:578-586(July 10, 1921);Paper Trade J. 73, no. 16:40, 42, 44(0ct. 20, 1921).

The general principles of the tasting of the ctrcngth of beams.may be applied .to the tooting of the rigidity (or clastLcity) of --

cardboard. If a strip of cardboard is placed-on two supports at adistance 1 apart and subjected to a load P at its center, the deflectionf is (iP37/4E I, where E is the modulus o' elasticity and I the momentof inortia of the section. In the apparatus used, a strip 1 x 10 cm.is supported on knife edgeo exactly 50 mm. apart, so that 25 mm. projectat either end. A graduated lever, pivoted at one end, carries a thirdknife edge, by moans of which the load is applied to the middle of thetest strip. The weight of the lever and knife edge is counterbalancedby moans of an adjustable counterpoise and the load :is carried bymeans of a rider on thi lover arm. The deflection on applying theload is road by moans of a mirror fixed to the lover and a scale graduatedin mm. If d and D are the distances of the deflecting cnife edge and ofthe scale from the mirror, P the equivalent load at the center of the teststrip, n the reading on the scale and c the thickness of the board, E =6250PD/no3 d. The limit of accuracy is not greater than 6%. If the tootabip is folded completely over (presumably without creasing), weightodin this position for 15 minutes, released, and allowed to stand forseveral hours, it will finally attain a definite "fold angle" whichvaries from 20 to 25 degrees for very rigid cardboard to 60 dogroos forroofing felts. Comparative tests on various samples can be obtainedonly by applying the test in exactly the sane nannor in each case. If

properly carried out, this test will class boards in the sane *ordcr as thedetcrmination of the elasticity.

611. Jacobsen, P. M. Hoffoann. Evaluation of pulp and the propertiesof paper. Svonsk Popporstidn. 35, no. 8:267-268, 273-274, 277-27,(Aril 30, 1932); Papior-Fabr. 30, no. 39:577-579(Scpt. 25, 1952);T. S. 97:131; B. I. P. C. 2:289.

A simple stiffness tester is described, in which the paper strip

(30 rm. wide) is supported on a concave surface by moans of a cylinder;shot is dropped onto the paper until it bonds; the weight of shot is ameasure of the stiffness.

612. Kottc, --. New stiffness tester (Taber) for paper and pulp.Zcllstoff u. Papior 19, no. 3:142-143(March, 1939).

This is apparently a translation of the nanufacturcr's announcncntof the V-5 stiffness gagc.

.J . Martin, R. I., and Bray, G. R. R. Flexibility or stiffnesstests, using the flexoncter. World's Panor Trade Rev. 100, no. 26:2008,2010, 2012, 2014, 2016, 203.8, 2020, 2068(Doc. 29, 1933); Paper-Maker 87,

:*: no. 1:4, 11-13(Jon., 1934)'; B. C. A. 19534B:90; T. S. 99:106; C. A. 28:2897;B. I. P. C. 4:138.

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Determination of the relative flexibility or stiffness of thinsheet electrical insulating materials by means of the flexometer(Pierce, J. Textile Inst. 21:T477(1930)) promises to have applica-tion to papers (both untreated and varnishqd) and other materials.With many materials the plain rectangular strip specimen curls andkinks, sometimes to such an extent as to make any reading impossible;-in such cases, by using a-pear-shaped-loop specimen much more-con-sistent roadings were obtained. The method of making the test and ofcalculating the results is explained.

614. Maston, Ralph A. Stiffness tester. U. S. patent 2,092,809(Sopt. 14, 1937); T. S. 106:95.

The'test sheet, of definite length, is clamped on a rotatablymounted arm. A freely movable pointer, pivoted coaxially with thearm, has one end positioned so as to contact the free end of thetest strip. The arm is rotated so that the test strip causes a de-flection of the pointer until the deflection of bending of the stripcauses it to slip off the end of the pointer arm. The stiffness ofthe test strip is obtained from the maximum deflection of the pointer.

; . ..615. Micoud, . Rigidity of cardboar d]. Papier 34, no. 2:251-252, 255-258(March, 1931).

The cardboard is cut into strips and each strip is fastened ina clamp in, such a manner that the length of the strip extending outof the clamp is exactly 20 cm. The weight of the strip causes it to

bend and form a parabolic.curve. The curve is more or less flat, de-pending on the stiffness and the weight of the board. When the paper

has no stiffness at all, it will fall down. almost vertically; and whenit possesses absolute rigidity, it will remain perfectly horizontal.The distance through which the board bonds is characteristic of thestiffness. Stiffness increases with the weight per sq. n. The de-flection of the strip diminished more rith increase in weight persq. m. with samplcr cut in the machine than in the cross machinedirection.. Moisture diminishes the stiffness of the board. The com-position of the pulp, the nature of the sizing, the method of boatingand the calcrC.cring all have on effect on stiffness.

616. Miror, Charles A., and Minor, Jessie E. A study of stiffnesstesting of pa-ers. Paper Ind. 17, no. 1:35-37(April, 1935); C. A. 29:

4578; B. C. A. 1935B:623; T .S. Cl:300; B. I. P. C. 5:250.

A study of the stiffness of tag, index, bond, and ledger papers,carried out mostly on a Curlcy stiffness tester (with a few tests onthe Suvant instrument), gave the following indications as to the valueof stiffness testing for paper quality. Stiffness is largely a matterof manufacturing manipulation and is, therefore, not a factor of fiber

quality except in so far as different kinds of fibers are subjected todifferences in manipulation, as in beating, in the sizing added, and inany other sources of fiber cementation. For the heavier papers, stiffnessis much more sensitive to beater hydration than is tearing resistance;

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it is also probably less sensitive to fiber weakness and to the shorten-ing of fiber length than is tear. For thinner papers which are beatento noximran strength, as aro bonds and ledgers, stiffness has no partiou-lar advantage in sensitivity ovor tear; for such papers stiffness bringsless distinction between rag and wood papers than does tear. Stiffnessfor some grades of paper should be a valuable test as a noasure of boaterhydration. - - -

617. M:lhonen, E. J. Strength and stiffness of white wood fiber-board. Firnish Paper and Tinber J. 17, no. 12:592,'594-596(Junc 30,1935); T. S. 103:82; B. I. P. C. 6:132.

A conpletc description is given of the use of the Smith-Tabor stiff-ness tester, and a comparison is made of the Mullen strength, freeness,and Sith-Taber readings for a sannpl of fiber board.

6l1. Paper softness testers. Instrunmnts 7:78(April, 1934).

Two new paper softness testers are announced (by the Thwing In-stiuaCent Co.), one for routine testing and the other for research work.

619. Paper stiffness tester. Paper Ind. 14, no. 2:141(May, 1932).

This tester is manufactured by the Toledo Precision Devices, Inc.but was originally developed by Rcnington-Rand,. Inc. (cf. Stuart, W. H.).It is mounted on a Toledo paper rean autogage and consists of a specialbracket supporting on adjustable loading nouber which contacts one endof a sample to be tested. The other end of the test strip rests on analuminum plate on the scale am. In testing, each strip is inserted inthe gap between the aluminum plate and the end of the plunger. Thehandle is turned slowly and steadily to bend the paper. The pressure isindicated on a chart. The naxinmu point regiEtored represents thestiffness.

620. Papcr tests for special properties. 4. Rigidity. Paper-Maker 87, no. 2:TS51(Fcb., 1954); B. I. P. C. 4:162.

The importance of rigidity has increased since the advent of auto-matic focders which speed up the flat-bed printing machines. Beatingis an important factor in producing rigidity; good fiber length andaddition of starch and silicate of soda nay also increase the degreeof rigidity. Records of tests for rigidity should be kept when it isascertained that the tests have been conducted under standard andnormal conditions.

621. Pcirco, F. T. The inandlc" of cloth as a measurable quantity.J. Textile Inst. 21:T377-416(1930).

i'.- L An instru-cnt is described on which it is possible to measure the; - anGlo through wilich a specimen of cloth droops when a definite length

,;SI , - is held out ovcr an cdge. By neans of a natlheratical forrula, this angle.; - is converted into a trln called the bending length of the material

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- Stiffness,- Softncss, Rigidity 221

(i.e., the length of fabric that will bend'under its own weight to adefinite extent); the stiffer the material, the longer the bending

.. _... length. The standard procedure for determining the bending lengthnay be varied with regard to the shape -and dinonsions of the-test-- - _specimen for very stiff or very limp materials. Although developed

- - -- for textiles,-the principle night be applied to the testing of paper.

622. Ricsenfold, E. H., and Hamburger, T. New stiffness testerfor paper. Papier-Fabr. 27, no. 46:709-710(Nov. 17, 1929); Zollstoffu. Papier 9, no. 12:841-842(Dec., 1929); World's Paper Trade Rev. 92,no. 25:2262(Dec. 20, 1929); Papior 33, no. 2:187-188, 191(Fob., 1930);C. A. 24:3366; T. S. 91:205; Paper Ind. 12:585.

The paper is held in a horizontal direction and supported ateach aen, or it sags in the center of its own weight. The angle ofthis bend is measured. The paper strips are 15 x 120 in., and 100 Mn.project beyond the clamp. After being in place for 15 minutes, theangle between the vertical through the point of clanping and a linethrough this point and the free end of the strip is taken as the measureof the stiffness. The weight of the paper and moisture content areinfluencing factors.

I- .- :623.. Saxl, Erwin J. Physical testing of rayon yarns and staplefiber. In Rayon and Staple Fiber Handbook, 3rd ed., 1939:554-565.

- A discussion of the Saxl tester and the Schiofor flexonctcr.22 references arc given, all pertinent ones being contained in thisbibliography.

624. Saxl, Ervin J. The quantitative measurement of stiffnessand resiliency. An. Dycstuff Rcptr. 27:P65-69(Feb. 7, 1938); RayonTextile Monthly 19, no. 1:57-58; no. 2:77-78(Joa., Fob., 1953); C. A.32:2363.

A stiffness tester is described, which was designed for cloth oryarn, but which night be applied to paper. It consists of a clampin which the test spccinon is inserted and a balance (with slidingweights) with a scnsitivity of 0.02 gram.

625. Schooller, F. Method of dctcrmnininG the bending elasticityof pliable materials, especially carton papers. German patent 646,253

-:i: (May 16, 1954).

626. Schulz, H., and Ewald, W. The stiffness of paper and its.] nmeasurenent. Papier-Febr. 23, no. 48:768-770(Nov. 25, 1925); T. S.

83:52.

!i2 .;' "A strip of paper, 20 nil. wide and 80 rr.. long, is fastened hori-zontally and a weight io added until the strip bends. The distance

Ai"& ., of the weight from the fixed end of the paper indicates the stiffnesso'' o the sanple.

N2i


627. Shamaan, C. F. The stiffness of paper. Proc. Tech. Section,Paper Makers' Association Gt. Britain Ireland 23:251-241(Dec., 1942);B.--I.-P.-C.-14:20; B. C-.-P.-A-. 1943B, II:346.

Because of the difficulty of measuring-the stiffness of paper-bythe usual static method, a dynamical method is proposed in which an -elastic restoring force derived from the stiffness of the paper controlsthe vibration of an inertia system of long period. The paper strip iscut in the required direction, accurately parallel, and of the standardwidth (2 inches); It is then formed into a ring tightly round a nandreland its t)o ends are clamped together by a screw clip, which fits intoo groove nilled out of the mandrel parallel to its axis. The clipcarrying the paper ring is screwed in position on the bob of a pendulum.The free period .of the pendulum is measured after it has been adjustedby cans of a leveling screw to a value of about 8 seconds. The nextstop is to fix the side of the ring remote from the pendulun, which isdone by means of a largo rectangular block which slides on the baseplate and carries a linear clanmp which can be slipped over the ringand screwed up tight without disturbing the pendulum. The coupled periodof the pendulum is now measured by tiring several sets of ten completeoscillations. The oscillations are conveniently initiated by means ofon air jet from a rubber bulb directed against the bob. The linearrelation between the displacement and the force applied to the paper ringwas confirmed by a static noethod for displacements up to 3 cm. on aring 22.25 rn. radius. The close correlation which exists between thesubstance and stiffness allows the individual stiffness values to becorrected to the nominal substance if the actual substance of eachsample is neasurod and the result can be expressed as the averagestiffness in dyne-cn. at the nominal substance. A linear relation existsbetween relative humidity and stiffness; adequate accuracy of stiffnessmeasurement is obtained if the relative humidity is controlled within+ 16. The nathenatical theory of the paper ring is developed.

628. Srlith,. George H., and Taber, Ralph F. Apparatus for menasur-ing the stiffness of flexible materials. U. S. patent 2,113,389(April 5, 1938); T. S. 109:149.

The test strip is mounted vertically in a suitable yieldable holder.The top of the strip is deflected by means of a pivoted pointer whichis moved annually over a suitable graduated scale to the position whorethe test strip disengages front the pointer and springs back. The scaleis graduatedd on either side of' the vertical, so that readings can betaken by bending the sane strip in both directions. Means are providedfor increasing the ronge of the instrument according to the type of materialto be tested.

t. >629. Smith, S. F. The rigidity of box board. A nethod- of measurementand some results. World's Paper Trade Rev. 99, no. 6:403-404, 406, 4o8, 442,444, 446; no. 7:4853, 486, 520, 522, 525-526(Fcb. 10, 17, 1933); Proc. Tech.Section, Paper Makers' Assoc. Gt. Britain Ireland 135, part 2:429-448;discussion, 448-450(March, 1933); Zcllstoff u. Papier 13, no. 4:158-159(April, 1933); Wochbl. Papicrfatr. 64, no. 20:342-3544(May 20, 193355); C. A.

-. g 27:5818; T. S. 98:15.


The tern rigidity is used in the special sense of stiffness--i.e.,.resistance to bonding through a snall anglo. The,present ncthod oftesting depends upon the estimation of the force required to deflectthe center of a strip of board through a definite distancewhen.the end s..-- -of -th trip are froo and rest on two rollers. The measurement is Madebelow the point at which the board takes on a sot--i.e., below theelastic linit. A strip of board 3 cm. -wide and a convenient length,usually 12 cn., rests on shoulders at the base of the supporting rollers,which are 10 cn. part. Pressure is applied to the center of the stripthrough a roller on the bottom end of a pointer, whose upper end travelsover a scal- showing the horizontal travel of the roller in rn. Thesanplo is held in place before pressure is applied by the pointer, whichis exactly balanced at the pivot except for a horizontal projectiongiving rise to a sarll sustaining force sufficient to hold the sanpleagainst the roller. Tlc pressure is applied by a weight arrm pivotedindependently on the sane spindle as the pointer, and having a stopwhich maintains it at right angles to the pointer while the weight isbeing applied. There are two positions for the weights on the weighingarm one being exactly twice the distance of the other fron the fulcrun.Four weights nay be used, 3.33, 12.5, 50 and 100 grams. Details aregiven of the ncthod of conducting the test and calculating the results.Certain precautions are outlined. The pressure on the sample is indc-pendent of the readinC of the pointer. The construction of the appara-tus is such that the pressure is applied only on the center line ofthe test strip when the scale reading is zero. At any other reading,it takes affect at sonm point above the center line and at the highotreading coinonly obtained, (at 6 nr. ) tho point of contact has risen0.48 rml. At least four sannple are used for an average result. Therigidity of a board is proportional to the cube of its thickness, thedensity being constant. It is also proportional to the square of thethickness, the substance being constant; at a given thicmknss, theri-idity is proportional to its density; nathcrmtical proof is offered.Fron these orlations nay bc derived the equation: Rigidity = K x(thickness) x density, in which K is tcmed the rigidity constant.Values for K have been dotcrmined for a variety of boards; it has acharacteristic value for each distinct class of board. Fron the op-proximntcly constant value of K for each type, it follows that rigidityof a board can be calculated with fair accuracy if its type, caliper,and substance are known. Practical mnthods of controlling rigidity arediscussed. A theoretical discussion of the nature of rigidity is included.

630. Srmith-Tabcr. Duo-rar:o snap tester. Advcrtising leaflet,-; - n. d 1 p.

An apparatus for ctrmininC the initial stiffness of paper frontsubstance 2°- to 15-point bristol. Toot speciEons 1.5 x 3.5 inchesarc clanpcd in the pepdului: and the pointer is ilovcd slowly across thescale tc the position whore the string slides front beneath the finger,ago anc srnps back to vertical. The overage of the right rd. left

scale rcadirgs represents the initial stiffness.

'.';. ~ 631. Snith-Tabcr. The Snith-Tabor pliability corpnrator. Smith-i-. Tabor Dull. 535. n. .

* . * ~;- a: 4-' -- ' -'


The apparatus is illustrated. The sanple to be tested is placedin the clamp and the dial rotated. The reading is taken when thesample touches the gage. Tho operation is repeated against the oppositegage. The averages show the .pliability in. one direction. -To dcterminc - ---the pliability the opposite way of the grain, the clanp is loosenedand samples turned 90 degrees. To doterdine the resiliency orelasticity, the pliability test is-carried-out; thoesanplo being allowedto remain bent from 5 to 30 minutes or until the plastic flow hasceased.. Rotate the dial until material tends to leave the gage, takereadings, subtract the average pliability and average resilience readingsfront 100, divide the basic result by the pliability results and multiplyby 100; this gives the resilience in per cent.

632. Stiffness of paper. Zellstoff u. Pepier 6, no. 2:77-78(Feb.,1926); T. S. 83:112A.

-:'; ,-The stiffness test for paper and its interpretation are brieflydiscussed. The article is a review of a paper by Crolard in Mon.

papeterie Frangaisc.

633. Stuart, W. H. Paper stiffness tester. Paper Trade J. 93,

no. 21:39(Nov. 19, 1931); C. A. 26:842; T. S. 94:191.

~S ^ The equipment consists of a Toledo scales and a Black and Decker, '.: drill stand with special vertical shaft, coil spring, collar, and test

strip holding plate. The test strips are placed between the end of thescale beam and the plunger of the stand. Pulling the hand lover on

' the stand forces the plunger down and bends the test strip (1 x 3 inches).

':; 634. Tabor, Ralph F. Apparatus for measuring the stiffness ofi^' flexible materials. U. S. patent 2,063,275(Dcc. 8, 1936); T. S. 105:104.

The invention provides a pair of relatively movable members for" ' bending the test strip with suitable means for limiting the movement

of the members in each direction relative to each other. A separate[t .' handle or lever, that may be operated either manually or mechanically,

is provided for operating one of the members. The motor used fore chanical operation is controlled so that it will stop automatically

' when the strip has been flexed the desired amount, and signalling moans. .tf,' are provided to indicate when this stage has been reached. Means are

': W provided for measuring both the initial and basic stiffness of the,'"i ' material so that the amount of plastic flow can be determined and the

. elastic properties of the material calculated therefrom. Cf. Smith and' Taber, U. S. patent 2,113,389.(No. 628).

b' "' 6535. Taber Instrument Co. Stiffness tester. Instrumcntn11:164

(1938); J. Textile Inst. 29:A554.

A very brief announcement of the V-5 stiffncss gage and triple-

/- !cut shear for mcasuremont of stiffness and resilient qualities of paper, etc.

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636. Taber Instrument Co. Taber V-5 stiffness gauge. Leaflet,1938, 6 p. Bull. 3802, Rev. 1.

The weighing system is of'the pendulum type. The face of thespecinmn clamp is mountedexactly on.the center of rotation, -insuring- --.-constant length of the moment arm. When the load is applied to thefree end of the test specimen, a torque is imposed on the holding means

-that--is-accurately weighed by-the deviation of the pendulum from thevertical. Indication is made by the simple alignment of the penduluminsot with the 15-dogrec angle graduation on the loaning disk. Undersustained loading the test specimen, especially, if it is one of thesofter materials, exhibits considerable elastic fatigue in the form ofa drift to a lower stiffness. The first registration of the linesindicates initial stiffness which should be recorded; additionalreadings are taken until no further change occurs over a period ofone minute. The last reading represents the normal stiffness. Afterthe first reading there will be noticed a residual deflection ortemporary set that slowly decreases and may eventually disappear. Thenormal oscillation of the pendulum between tests tends to neutralize'.this residual force and should be prompted, if necessary, by manuallyoscillating the pendulum weight back and forth a few times.

637. TAPPI. Rigidity, stiffness and softness of paper and paper-board. TAPPI Tentative Standard T 451 m-44. Paper Trade J. 111, no.22:125-124(rlov. 28, 1940).

Rigidity is defined as the property of a paper or paperboard ofresisting an applied bonding force, its fl.oxurcl resistance, and isproportional to El, where E is Young's modulus and I the moment ofinertia. Stiffness of paper or paperboard is its ability to supportits own weight, the inverse of flabbiness or limpness. It is propor-tional to EI/W, where W is the basis weight. The softness of a paperis the feeling of softness when a shoot is crumpled in the hand. Thisdeopnds upon the case of crumpling,together with the absence of sharpedges in the crumpled sheet. It is inversely proportional to therigidity ElI modified by a function of the thickness of the shoot. Themethod is a nodlification. of that of Clark.

656. Technical description of Smith Taber Model 'E" precisionstiffness tester. Smith Taber Bulletin E-10133. n. d. Paper Trade J.97, no. 22:22(Nov. 30, 19553).

A general description of the apparatus and its applications.

639. Thwing-Albcrt Instrument Company. The physical testingof paper--tonsilc strength of paper. Thwing'c Papor Tester 1, no. 2(1936). 4 p.

A general discussion, including definitions, significance andinterpretation of results, application of tensile strength, testmethods, cutting the test strips, home-madc apparatus and corzeorcialinstruments.

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640. Vaughan, Leonce, Jr. Device for measuring stiffness ofsheet material. U. S. patent 2,044,411(June 16, 1956); T. S. 103:580.

The apparatus provides for means to lead the free margin of a-. _ --- shcet,-which is secured along -it oppdsitoo parallel margin, by means of

a weighting chain, one end of the chain being provided with an elementby means of which it may be.readily attached -to or- detached from the - -

shcot, and mechanism being associated with the chain for rapidly addingto or subtracting from,' under the close control of the operator, thatportion or part of the chain which is actually supported by the freecdge of the sheet. The weight necessary to bring the free margin ofthe sheet undergoing toot into a predetermined position may be addedto the free margin thereof. 'he chain weight is suspended in spaceand offers no resistance to horizontal movement of the free margin ofthe shc-t. The apparatus consists of a base, sheet margin retaining orholding mcans, and weight-applying mechanism.

641. Withanm Goorce S., Jr. Papcr-Tostor. U. S. patent15,35,l64(July 19, 1922); Canadian patent 214,457(Nov. 29, 1921);Pulp Paper Mag. Canada 20:885; Paper Trade J. 74, no. 19:58.

An instrunmnt for testing the flexibility of paper comprisinga support in which a sample of paper to be tested is loosely mounted,

.''S:t1' a bending device for bonding the paper both longthwice and crosswiseof thc grain and. for moving the paper flatwisc through the support,a liquid receptacle connected with the bending device and a calibrated

;. . tube for delivering liquid to the receptacle.

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227

STRETCH

642. Apparatus for determining the effect of moisture on thestretch and shrinkage of paper. Paper Makers' Mo. J. 65, no. 1:19,21(Jan., 1927).

- - A British instrument for measuring the stretch of paper whenmoistened and its shrinkage when dried.

643. Carlson, T. A. Study of corrugated fiberboard and its com-ponent parts as engineering materials. Fibre Containers 24, no. 7:22,24, 26, 28-51, 34-35(July, 1959); B. I. P. C. 10:31.

In a test designed to show a stress-strain relationship, aTuckcrnan optical strain gage was used aomoans of measuring the stretch.The specimens of board, 1 x 6 inches in size, are clamped in a horizontalposition, each clamp overlapping the specimen by one inch. The opticalstrain gage, which measures the cxtention in an initial length of oneinch, is placed at the middle of the 4-inch portion of the specimenbetween the clamps. The rear clamp is attached to the dial scale bymeans of a flexible chain passing around a ball-bearing pulley mountedbehind the box. The dial scale is hung from the movable head of a box-testing machine and tension is applied to the specimen through the scaleby operating the movable head upward at the desired speed. Si-iiltaneousreadings of stretch and load arc made until a currently plotted stress-strain diagram shows that the proportional limit has been passed. Thegage is then removed and the application of load is continued until thespecimen breaks. With the 1-inch gage used for the tests, redings? to

0.000,004 inch can be obtained. The gage has a capacity of about 0.005inch but it c'p Je reset during the test and the stretch to naxinurcload determined. A scale of 150-pound capacity is used for testliners. Another scale of 50-pound capacity and graduated in 0.1 poundis used in testing corrugating papers.

- 644. Clark, James d'A. Some observations on burst, tensile,ana stretch tests. Paper Trade J. 102, no. 2:40-42(Jan. 9, 1953);Tech. Assoc. Papers 19:264-266; discussion, 90-94(Junc, 1936); 0. A.50:2578; 3. C. A. 1936B:186; B. I. P. C. 6:275; T. S. 103:193.

Data are given to show the effect of rate of loading or thestretch of a sulfite ledger paper and also the variation in resultsfor stretch obtained by a :iunbor of cop rating lab.jrat-oris.

645. Fcnchol, K. Manipulation of the apparatus for testing theelongation of paper in water. Papicr-Fabr. 24, Fcst-u. Auslandhcft1926:98-105; T. S. 84:279.

A description is given of the new Schopper water-elongation testerfor paper. The stretch properties of paper, either after inmorsionin water or exposure to moist air, can be ascertained with this oppara-tus. Actual tests of samples immrsed in water for one minute andthen allowed to stretch for three minutes are reported.

I . - - _ -

Stretch 228

646. Harrison, R. Paper stretch recorder. lorld's Paper TradeRev. 101, no. 21:1698,-1701(May 2 5, 1934); B. I. P. C.-4:277; T.-S.-100:78.

A brief description and illustration is given of the Nogrotti andZanbro stretch recorder. The sample strip of paper up to 6 inches longanti about 0.25 inch wide is held by a r.anll spring clip at each end andis suspondc d-from a loo6klaft the top 6f the supporting fraoe, the bottom.clip being attached to a lint connected with a crank of variable

-.... -longth on thn open-orn spindle. A small countorbalanc-c weight kccps---tho paper in tension;. Aftcr counting the sample, the recording pen issot to a suitablec position on the chart by mnans of a screw at the topof the supporting frano. This novos the top suspension hook verticallyover a small rangb. The tubular cover is then placed over the paper-supporting franc and conditioned air is passed over the sample byconnecting the top of the tube to suitable humidifying or drying appara-tus. The chart is arranged so that coach division represents an altera-tion in the length of the sonple of 0.002 inch and the full pen travelan alteration of 0.1 inch. If the sample is 6 inches long, this representsa 1.6% alteration in length.

647. Henning, Hans-Joachim. Device for measuring the elastic

properties of materials. U. S. patent 2,070,731(Fcb. 16, 19537).

A swinging pondulun acts through the modiunm of controlling neansupon the test piece by a piston. The controlling nmans connect thependulum and the piston at an adjustable Doint and sever this connectionat another adjustable point, so that the amount of work done on thetest piece during the swings of the pendulum--i.c., the work donebetween the beginning and the end of engagement of the pcndultun andpiston--is always the sCae. The power by which the nmatcrial opposesdcfornmation acts against the attacking force, whereby the total workof the pendulum is reduced, resulting in a lose in omplitudc, so thatthe pendulun approaches a position of rest noro quickly than if itswings freely. Thic decrease in caplitudc furnishes a basis for cal-culating the elasticity of the material.

648. Institute of Paper Choneistry. Mecauromnot of the stretch ofpaper. Paocr Trado J. ll8, no. 26:12-16; 119, no. 1:24, 26, 28, 30;

no. 2:24, 26, 28, 30(Juno 29, July 6, 13, 1944); B. I. P. C. 14:414.

The signlilcanco of stretch and the load-olongation curve are dis-cussed briefly. Theo nosuronent of stretch by moans of the A-r.thor uni-versal tondsile strength tester, the Clark stretch tester, the Schopperelectrically driven strength totter, a:nd the Scott Scrigraph is exaninedin sonc detail. The principle of the Scott ScriJgraph is satisfactory.T'he particular r-odel used in this study was of rather low sorsitLvity.The stretch indicating nochanicn of the Schoplper instrniment is dynamicallyunbalanced to such a degree that the indicator jumps to higher readingswhen the instrunont is jarred by the failure of the cpccimcn. This faultwas temporarily minimized by counterbalancing. The Pnthor and thecounterbalanced Schoppor instruoents agrc fairly well but indicatestrobchcs which arc seriously high, as compared with values obtainedwith the Scott instrument. The reason for the discrepancy rests inthe fact that both Anther and Schopper instruoento are so designed as

I I '.. -.- pM';s -or

Stretch 229

to include in the indicated stretch or elongation reading some of theelongation which occurs after start of the specimen failure. Stretchvalues obtained with the Clark instrument tend to be less than thoseobtained with the Amthor or Schopper instruments. The elongations

measured with this instrument also include part of the failure elonga-tion mentioned above, although a smaller part than those measured withthe Amthor and Schoppor testers. The Clark tester was not comparedwith the Scott instrument. Corroborating published results-of otherworkers, it was found that stretch decreases as the length of thespecimen increases. Contrary to suggestions in the literature, testswith two papers showed no change in stretch with change in rate of

loading, and showed that stretch tends to increase with increase inspecimen width.

649. Koester, Homnan. Paper stretch tester. U. S. patent

1,885,209(Nov. 1, 1932); T. S. 97:222.

A series of paper strips of uniform length and width are rigidly

secured at one end within a closed chamber through which suitably condi-tioned air is circulated. The free and of each strip is placed underuniform tension, which is the same for all strips, and each strip isconnected to a suitable indicating number whereby any change in lengthdue to stretching of the paper will be registered in such a way that

comparison may be mode among the various samples under test.

6_0. Mandl, K. Testing cigarette paper for elasticity. Oesterr.

Zontr. PFpicrind. 40:115-117(1931); Zollstoff u. Papier 11, no. 6:

354(Juno, 1931); Boll. stoz. sper. ind. carton 10, no. 6:77-78(Junc,

1931); Paper Ind. 15:911; T. S. 93:276.

Strips of paper of a definite length are wound around a pin whichis rotated. The strips are held fast to the end which is rot woundaround the pin. The incomplete return revolution of the pin when

it is released is a measure of the elasticity of the paper. The appara-tus consists o' a tube which is rotatable and which is clotted for in-troducin,, the paper strip, of a stopping device for the frc end of thestrip, and an indicating device for shoving the angular rotation of the

tube. In ordor to secure more certain fastening of the paper strip, asecond tubc is inserted with the outer tube. The second tubc is carried

along by the outer tube by friction and carries the indicator which travelsover the scale. The indicator is loaded with a weight which brakes the

back rotation and is so dimonsionod that the graduations on the scale

correspond to about gram weights. The crank of the instrument is turned.'.so that the indicator passes through an anglo of 360 degrees; the crank

is then released and the shaft is allowed to be rotated backwards by the

elasticity of. the paper. The cxtent of this back rotation is a measureof the claDticity of the paper.

651. Sindall and Bacon. Stretch and expansion of panors. Paper

Mnkors' Mo. J. 50, no. 5:159-160(May, 1912); Paper 7, no. 153:23-24

(June 12, 1912).-A31i1'A

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Stretch

Preliminary experiments on the stretch of esparto printing paperswere carried out by placing papers (having two lines exactly teninches apart, the weight of the papers being known) between damp.shoots of- blotting-paper for-12-hours, after-which-the distance-between -the two lines was measured and the weight of the wet strips determined.No conclusion could be reached as to the relation of the csparto contentand the amount of expansion.

652.. Stretch and shrinkage in paper. A new Schoppor apparatus.World s Paper Trade Rev. 86, no. 16:1244(0ct. 15, 1926).

A brief description is given of the Schopper apparatus which isdesigned to measure the stretch of paper when moistened and its shrinkagewhen dried.

653. TAPPI. Stretch of paper and paperboard. TAPPI Standard 457 m-42.2 sheets. Paper Trade J. 102, no. 8:132-133(Fcb. 20, 1936); 115, no. 7:39-40(Aug. 13, 1942); Tech. Assoc. Papers 19:270-271(Junc,- 1936).

The test result includes not only both the elastic and the inelasticstretch of the paper up to failure but also the small distance throughwhich the broken strip will elongate during the test while being holdtogether by protruding fibers, as this factor prevents the indicatingmechanism from being released at the reading when the break starts. Forthis reason, the test may be termed more correctly 'the percentage clonga-tion of a strip of paper up to, and partly including, rupture undertension." Details are given of the apparatus, calibration, and procedurefor making the tent.

230.

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231

TAPING AND JOIN~T TEST

654. National Association of Purohasinc Aqgents, Inc. CorruGatedfibreboarO shipping, containers. No- 19, 19341. 8r -)

Tnaphy and Joint Test. There is no established procedure fortestinc7 manufaobuzoivris-jointc- If a taped joint, the quality-and appli--

cation Ct fl tape uhoulif bo determined by a careful. inspection. If.a:iy doubt ar'-sc-s as to the quality of tape used, separate samples- ofin'uuad tone shctJld be secured, identified as the soae as that of therdcnuft-ctu~rcrs 'joint, and tooted for tea:?rin otrongth asheinfr

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232

TEARING STRENGTH

655. Ainslie, R. A. Uses and limitations of some paper-testinginstruments. Proc. Tech. Section, Paper Makers' Assoc. Gt. BritainIrclandl17, part 2i473-8RPi;-d.iscussibn, 468-492(1March, 1937); Wcrld'sPaper Tr-o.e Rev. 107, no. 13:TS8-12; no. 21:TS28-32(April 30, May 21,1937);. Paser.-Mkor 93, no. 2:TS26l31(Feb., 1937); B. I. P. C. 7:276;B. C. A. 1937B:228; C. A. 31:6876; T. S. 106:93.

When assessing the quality,of a paper for general strength, itis usually Just as important to know the tearing strength as the burst-ing and tensile strengths. The main uses of the tearing resistancetest are: (1) For controlling the quality of the product on a machine.Since a single operation on a sample tears several inches of paper, areliable result can be obtained with fewer tests than is the case withbursting and tensile testers. (2) For investigating the effect ofbeating and furnish on the average fiber length of paper. (3) Forspecifying the'quality of a paper, particularly where toughness ratherthan a hard craclkle is required. .The limitations are: (1) The moisturecontent of the paper may affect the test results more than in thecase with tensile and bursting tests. (2) The number of sheets torntogether in a'test may affect the calculated result for a single sheet.This may be caused by the friction of torn edges over each other,altcredcconditions of stress, or variations in the rate of tearing.With readings of 20 to 60, the variations are not appreciable. (3)Instruments of the Elmondorf type do not measure the initial forcerequired to start a tear but only that required to continue a tear.Resistance of the starting of a tear appears to involve a combinationof tensile strength and stretch. (4) The necessity of checking the zerosetting of the instrument regularly, preferably before each test.(5) The stiffness of the material affects the results; this is a seriouslimitation when dealing with material such as boxboard. The Thwing-Elmcndorf tester is mach easier for cutting and inserting specimens butthe Marx-Elmcndorf'appoars to be more likely to give accurate andreproducible results over a long period. The factor given by the makers

of the Marx-Elmendorf for calculating the gram-weight per single tearfrom the actual reading is twice what it should be. It is suggested thatthe unit should be orgs and not grams-weight. The ratio of the Marx/Thwing readings (in the range between 15 and 70) varied from 0.99 to1.09 for the machine direction and from 0.94 to 1.11 for the crossdirection.

656. American Society for Testing Materials. T-ctative method oftest for internal tearing resistance of paper. A.S.T.M. DesignationD 689 - 42 T. A.S.T.M. Standards 1944, part III:358-361; A.S.T.M.Standards On arper and paper products, Nov., 1943:108-111.

This is similar to TAPPI Standard T 414.

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Tearing Strength 233

657. American Society for Testing Materials. Paper and paporboard--characteristics, nonenclature, and significance of tests. Philadelphia,Th6 Society, 1944.

Tearing strength. Tearing sttrgngth is a property of the inncr structure of the sheet, but surface treatment sometimes affects thevalues to a marked degree. Moisture content of paper has a large effecton its -toring -strength.--Tearing strength is an-empirical property, andis also in the class defining manufacture of paper. This is in part dueto the fact that the test is of long standing and widely used; hence itserves a useful purpose as a nill control test. The tear test cansometimes be interpreted to reflect the general nature of the fiberpresent in the paper as well as the beater treatment to which it hasbeen subjected. For example, the test will usually provide some indica-tion of fiber length and coemnting action. Ordinarily, a dense sheet givesa lower tear than a bulky one of the sane material and sane basis weight;and long fibers offer greater resistance to tear than short ones. Thetest has great significance in the requirements of paper which is to besubjected to tearing strain in conversion or in actual use. This wouldinclude paper used for'bogs, boxes, building papers, wrapping, tissue(except creped), and nany specialized industrial fields. As a rule,converters bf paper in these industries rely nore heavily on tearingstrength than on any other single property. Anong users of paper insheets ordered to specifications in the converting trades, the teartest will be used more often than most other standard tests, with theexception of the all-important basis weight and the venerable burstingstrength test.

658. Anderson, B. Tearing test for paper. Svensk Papperstidn. 25,no. 22:t05-406(Nov. 30, 1922); C. A. 17:2783; T. S. 77:161.

An original apparatus used at Vastcras is described, with a cut.It'is graduated in kg.-cm. The specific tearing work, R, is calculatedfrom the equation R = Ru/lnd, where Ru is the tearing work read frontthe scale, 1 is the length of the strip of paper tested, n is thenumber of parallel strips, and d is the thickness of the paper, all ex-pressed in cn. R/10 tines the specific gravity gives the tearing surfaco--the area of free hanging paper whose weight will cause the paper to tear.A table shows the variable effect of temperature.

659. Borgoao, Eric. The calibration of Elonndorf's tearing tester.Svensk Papporstidn. 45, no. 4:71-73(Fob. 23, 1942); B. I. P. C. 12:290.

After briefly discussing the general principles according to whichdynamic tearing testers (such as the Thwing-Elonndorf and the Poller-Elncndorf instrunonts) work, brief reference is nade to the calibrationmethod of J. d'A.Clark CNo. 668] which enables a correction factor(determined from a table or graph) to be applied to each observed value.A simpler procedure of sufficient accuracy for most practical purposesis outlined, which is based upon the adjustment of the tearing distanceof the sample sheets, sothat the instrument will yield approximatelycorrect values for an ordinary working rang. A graph is prepared for

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each tester in which the readings on the scale are plotted against thecalculated tearing distance for the range 3.9 to 4.9 cm. of the specimens.This yields a rather flat curve for the higher readings. From thisgraph it is then possible to select the proper tearing distance to useso as--to give- approximately- correct -results-over the -chosen working . - ---range. According to the TAPPI Standard, enough sheets must be torn atone time that all readings on the scale lic within the limited rangeof 20 to 40 groms, whicl ifs advantageous in this method of calibration.The author suggests that, rather than use the standard tearing distancefor testers of this type, each instrument should be calibrated and thecorrect tearing distance calculated for each individual tostcr.

660. Booth, H. C. Apparatus for measuring the mechanical conditionsof paper. J. Sci. Instruments 4, no. 1:5-8(0ct., 1926); World's PaperTrade Rev. 86, no. 24:1842, 1844, 1846(Doc. 10, 1926); T. S. 85:102.

It scomo reasonable to suppose that a method of estimating the mochani-cal condition of paper depending upon the measurement of the energy re-quired to tear a given length, rather than the force required to rupturea given width, is. likely to bo more consistent. It will be loes in-fluoncod by local variations, since it essentially consists in themeasurement of an integrated effect. The apparatus consists of a doublepair of flat clamps which hold the sample; it is passed through a wire

::,~ - loop or stirrun which is free to move in the spaco between the clamps.The loop io connected by means of a flexible cord to the lower end of a

*^-'S pondulurm, which is raised to a horizontal .position and which, on beingreleased, drows the wire loop through the paper. The pendulum swingswith negligible friction on a horizontal axis. The connecting cord isso attached that, after the loop has torn through the paper, it becomesdctachod from the pendulum and the latter is free to continue itsswing; it rises to a height which will vary according to the amount ofenergy which has beer uxpondeod in tearing the paper. The amount ofenergy oxpcnded will blso depend upcn the breadth and thickloss of thestrip. Tosts show that this energy is closely proportional'to the width

it is advisable to use paper which is originally of the same thickness.The values arc expressed in millions of orgs. The apparatus has beenused for tho estimation of the extent of deterioration that takes placein the paper dielectric of an electric cable.

661. Brccht, W., and Irnot, 0. A new apparatus for mnnsurlig-the tearing strength of naper. Wochbl. Papiorfabr. 64, no. 43:848-853(Dec. 2, 1933); T. S. 98:296; C. A. 28:6306; B. I. P. C. 4:113.

.:'-i : A now inctremtont is described in which the sheet is torn by aplunger operated by a lever. It permits tearing the sample in andacross 'th machine directions simultaneously and records the initial

';: -. tear and the tcar-through. It is claimed that the now device corrects': C GZone of the faults of- tho Elmcndorf tester. In geonral the results

obtainod, with the two machines are the sane. The time for ten testsi'':z with the EJ]cndorf was 7.5 minutes, for the now tester 3.25 ninutos

':iB.,;' (with practice as little as 1.5 minutes). .

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662. Brecht, W., and Imset, 0. The initial tear and the through-tear resistance of papers. Zellstoff u. Papier 13, no. 12:564-567(Dec., 1933); 14, no. l:14-16(jan., 1934); C. A. 28:2529; T. S. 101:132.

The manual initial tear and the through-tear (ripping) tests aretwo fundameiitally different testing procedures. The' results are notidentical and they cannot be substituted for each other. The mathe-matical treatment of the tests is given and-the mechanics of the tearing--

-- -resistances obtained is illustrated by several diagrams.

665. Brecht, W., and Imset, 0. Testing the Elmcndorf tearingtester, its method of operation and its importance. Papicr-Fabr. 31, no.27A:46-60(July, 1933); C. A. 28:1530; B. I. P. C. 3:291.

A method of calibration of the Pollor-Elmondorf tester, based onthe operating characteristics and estimation of friction losses, isdescribed; the results agree closely with those of the Clark method

, (Paper Trade J. 94, no. 1:33(1932)). Ihen a number of sheets are torntogether, the starting cut is not the same in all, because of poor

.:! design of the knife; there is a marked tendency for the outer shootsto split, an abnormally high tearing force being required; the frictionbetween tile torn edges increases the tearing resistance abnormally.

, ~. The errors from those sourcoo are separately evaluated, and shown to'i .ji reach 15% or more. Also, the relation of tearing resistance to weight

of sheet is not linear. To obtain reasonably concordant and usefulresults, the instnaent should be calibrated often and enough shootstorn to give a scale reading of at least 20 grams; the weight of theshoots should be quite constant; and the weight and number of shots

2 .i, torn should be reported. Not enough is Inown. as yet about the mechanism7: ' ,. of this conpl.x test to permit its use as a measure of fiber shortening

r '., in the manufacturing process.

Pap' e664. Carson, F. T. Strength with reference to machine direction.,. ' Paper Tradc J. 91, no. 14:64(0ct. 2, 1930); Pulp Paper Mag. Canada 30,

no. 23:639(Dec. 4, 1930).

:: T4 rA machine direction tearing t-st involves the tearing of paper so'/ M that the tear proceeds across tlie fibers which lie in the machine direction--

;. ~ that is, so as to rupture the machine direction fibers. It would seem; ,~ illogical to Epe6k of the machine-direction tearing strength when tearing

paper so as to rupture the cross-dircction fibers. Most people designatethe direction as tilnt ir which the tear proceeds, a practice which is in

' ,- confornity with engineeriing practice as applied to the shearing strengthof wood. To make the analogy complete, one should speak of the "resis-tance of tcaring long the machine direction. " The proposition of designat-

,ing direction in connection with the tearing strength of paper is open toquestion.

ii 665. Carson, Frederick T., and Snyder, L. W. Increasing the capacityi of the ELtecndorf tcoring tester. Paper Trade J. 86, no. 13:57-60(March 29,

1928); C. A. 22:3296; TS. . 88:199.

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In--tho Elmordorf tearing tester, a sector-shaped pendulum carriesa clamp which is in fixed alignment with a fixed clamp when the pendulumis in its initial position of mnaxinum potential energy during a tent.A specimen of paper is fastened in the two clamps, a slit is made in thepaper between the clamps as a starting point for the tear, the pendulum

_ - -' - . ris-rcloased, and the specimen is-torn in two -as-the moving clamp-moves-- --away from the fixed one. As the paper is torn, work is done upon it,

-_ which is ncacured by the difference in potential energy at the beginning and the end of the swing. Dividing the work done on the paper by thedistance the paper is torn (which is constant for all tests) gives the-result as a force--the average tearing force. Since the initial dis-placement angle of the pendulum is fixcd, the work done is a functionof the final displacement angle--or the angle between the vertical andthe line from the center of gravity perpendicular to the axis of rotation.The calibration of the instrument is accomplished by means of a formuladerived from the behavior of the pendulum. friction in the instrument,most of which is in those friction sleeve of the pointer, somewhat com-plicates the calibration. The derivation of the formula is given.The determination of the instrumental constants is illustrated. A simpleprocedure for the periodic adjustment of the instrument is described.The precision of tho tester is probably not better than 1%, because of-irregular variations in the instrument friction. A method is given bywhich the capacity of the tester was doubled. This was accomplished bymeans of a brass insert which was made to fit snugly in the open sector,

; .' and was fastened in place by means of lugs placed symmetrically withrespect to the center line. The weight of the insert was 2501 grams.The use of the calibration equation in designing the modified testeris discussed. The tester has boon used in studying roofing felts. Somesuggested improvements in the tter. atorar given.

666. Case, H. N. Strength teats for paper. Description of apaper tearing resistance tester. J. Ind. Eng. Chom. 11, no. 1: 1F9-51(Jan., 1919); Paper 23, no. 19:13-15(Jan. 15, 1919); J. Soc. Chem. Ind.38:169A.

Twelve strips, 1 by 2.5 inches, are cut from the sample to be tested,six with the long dimension parallel to the grain of the paper and 6across the grain. A quarter-inch slit is made in one end of the paper.The apparatus consists of a nothod of clamping the strip and water isallowed to flow into a bucket attached to one end of the strip untilthe paper breaks; the weight of the water in the bucket in grams is

.- -- : taken as the tearing resistance. If a tearing distance of more thanth As. 'i .. 0.25 inch is used, the poling effect will have nore influence upon the

~ ! ^.. results. Satisfactory results cannot be obtained by clamping theA, F -': .. strip in a Schoppor tensile machine and measuring the load required to:' ;," separate the two pieces. The exact rate of flow of the water is not.^ -:' . important. The following ndvantagos are cited: The comparative length;,? ?j;/, "of the fiber and the peeling qualities of the stock arc shown, i the

l;Y^. result. Sizing idocs not increase the tearing resistance to suchan-r · '';: o.extent as it does other tests. The apparatus is siniple and is applicable."- S^_ , to both li.ht end heavy papers. The amount of grain in the paper is

4S 4•- shown. Tlhe load is applied with on unchanging rate of increaseoo. How-·'*yv , - over, the testing is tedious and there is a wide variation in the results

l*~ A on a givon sample. In this it rosemblec the Schoppcr folding machine.

Tearing Strongth 237

667. Clerk, TFederic C. Paper testing methods: microscopical,chemical and physical processes described, with an account of theapparatus employed. New York, TAPPI Publ. Corp., 1920. 24 p.

A photograph of the Thwing tearing tester is given, with a verybrief description of-its method-of operation.; - . -.

668.- Clark, James d'A. Calibration of Elmendorftearing tester.Paper Trade J. 94, no. l:33-34(Jan. 7, 1932); Tech. Assoc. Papers 15,no. 1:262;-discussion, 77-80(June, 1932); T. S. 94:191; B. I. P. C. 2:203.

The instrument is leveled and adjusted on a level sheet of plateglass and a known weight (W grams), the center of gravity of which ismarked with a punched dot, is clamped to the radial edge of the sectorbeneath the Jaws. The sector is raised and set as for proceeding witha tearing test and by means of a surface gage or other convenientmeans the height of the center of gravity of the weight above the glassplato is measured (h cm.). The sector is then released, allowed toswing, and the pointer reading noted. Without touching the pointer,the sector is raised until the edge of the pointer just moots with itsstop, in which position the height of the center of gravity of theweight above the glass plate is again determined (H cm.). The workdone is W(H - h) g.-cm. If f is the average force in grams to tear.a single sheet of paper through 4.3 cm. (d) in the case of the Thwinginstrument or 4.4 cm. in the case of the Marx instrument, then the workdbne is 2fd. Thus W(H - h) = 2fd, or f = W(H -h)/2d grams. If theinstrument is designed to tear a single sheet, f should equal thepointer reading r. However, the Thwing instrument is calibrated so as toroad the force required to tear 16 sheets at one time through a distanceof 4.3 cm. or a total tearing distance of 68.8 cm.; thus, r shouldequal W(H - h)/137.6 grams. With the Marx instrument it is W(H - -s)/52.8grams. The difforoncc3 in results given by the. two instruments arcdiscussed; the Marx instrument at prosont is not calibrated so as togive grams force to tear a single sheet when 6 double tears or made,as roconmondcd by the makers, but half that nunmer; thus, six singletears should be made to obtain a direct reading.

669. Cottrall, Leslie G. Tearirn resistance of paper. Papor-Maker83, no. 3:TS127-132(March, 1932); C. A. 26:6130; T. S. 96:136; B. I. P. C.2:246.

Bursting and tensile tests may be carried out in what may be termedeither a static or ballistic manner. Previously the question of staticvs. ballistic conditions of testing has not been important in the case oftensile tests because static condition can be approximated and areinvariably used. Hovover, with tearing testers of the type of theElmondorf, in which the test is completed. in about 0.1 second and,therefore, these instruments test the tearing strength under conditionsapproximating to ballistic conditions ard may be termed 'ballistictcaririg testers." The ballistic condition of testing gives higherresults than the static condition; this has been investigated byCarson [No. 56] and an explanation has boun offered. The applar-tus fordetermining the tensile test of paper can be adapted to cnrry out a

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674. Elmendorf, Armin. Tearing tester. U. S. patents 1,423,841and 1,423,842(July 25, 1922); Paper 34, no. ll:484(July 3, 1924);Pulp Paper Mag. Canada 22:667.

. -- A-pendulum with a pointer attached is swung to its extreme leftposition. While it is in this'position, the paper to be tested is placed in the jaws-of the instrument, one of which is fixed to the framoand the other to the pendulum. On releasing the pendulum, the paperis torn for a length of exactly two inches and the work done decreasesthe distance to which the pendulum swings to the right, which is auto-matically measured by tho pointer. If the dial is graduated in degrees,the work can be calculated from the weight of the pondulum, the die-tanco of the axis of rotation to the center of gravity, and the initialand final angles which the pendulum makes with the vertical; or thedial mny be graduated to read the work done directly. The differencein the two patents resides essentially in the design of the pendulumand jaws. In the first patent the pendulum consists of a weighted armattached to a wheel and in the second it consists of a sector of a

4. -circle which is suitably graduated.

675. Elunndorf tester. Wochbl. Papiorfabr. 63, no. 15:286-2870 .. (April 9, 1932)..

A brief description is given of the Elmondorf tearing toster andsone of its advantage. In Germany it is handled by Firma F. R. Poller,

, ' .--". Leipzig and is known as the Pollor-Elnondorf tooter.

::;- ~ 676. Finch; J. M. Simplified tear test. Boll Labs. Record 21,:,A - no. 2:58-59(0ct., 1942); B. I. P. C. 13:111.

".P- ~ The Firch cdge-tear stirrup consists of a motal plate, roughlyY-shapod and abcut 6 inches long. This serves as the suspension bar andsidos of the stirrup. The transverse rmmber is a metal plato 0.025

Jl: inch thick cnd cut in a shallow V at tho-top. The upper edges of this Vare recessed and short lengths of 25-nil rod are inserted to give the

.,- s. ides of the V a smooth cylindrical surface that will not cut thematerial under test. A 1-inch strip of paper is passed through thestirrup and its ends bent down and fastened to the lower jaw of any

i"t convenient forn of tension testing nachino. The suspension bar of thestirrup is fastohcdo to the upper Jaw of the testing machine and forceis applied. Because of the V across which the test strip lies, theforce is applied to the strip at its two edges. As the force is in-creased, the strip ultimately tears from the edges toward the center

, -, and this force is used as a measure of the tear resistance.

i(% " 677~. Griuncwnld, --. The Elnondorf tearing tester. Zellstoff u.. S K Papicr 1, no. 8:232-233(Nov. 1,. 1921).

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onn narplo in torn four or noro tinrs. The text is given, without thedata, in Pulp Paper Mag. Canada 20, no. 16:320(April 20, 1922).

681. Houston, Paul L. A preliminary study of tearing instrumentsand tearing test methods for paper testing ..Natl. .Bur. Standards,--- -

. Toch. Papor o.' 194. July 27, 1921. 18 p.

.- - The first part-of-this-paper gives results showing that it isnecessary to cut test samples the same size in order to compare thetearing strength of papers. Three sizes were used: 1 x 8 inches,2-3/4 x 1-1/8 inches, and 4 x 10 inches. If the test samples are cutthe same size, very good check results arc obtained. From a study ofthe action of the paper as it was torn, it was evident that each fiberin the path of the tear receives assistance from all the adjoiningfibers as far as the edges of the test samples. The larger the testsample, the greater the amount of this assistance, provided that thebeginning of the tear was always the same distance from the end of thetest sample and just halfway across the width of the test sample. Thisis used as an explanation of the fact that the larger the test samplesthe grcoter the values of the tearing strength. Three instrumentswere used in this study; one was a tensile strength instrument; thesecond was tho'Thwlng tearing tester (termed a recording instrument);the third was a nonrecording instrument. The Thwing instrument isconcluded to be neither delicate, sensitive, nor accurate, since theamount of friction in the pin-slot bearing and the friction betweenthe pen point and the paper chart do not allow careful accurate cali-bration. Because the test results obtained by using different factorswill not check, there appears to be a defect in the mechanism of theinstrument. The paper sample is cut by means of a die in such a wayas to give five initial tears and a curve showing the maximum andminimum tear. There is greot doubt whether the five peaks in the curveactually represent five initial tears. The fibers very near the edgeof an angular slit in the test sample (or perhaps halfway betweentwo angular slits between which the paper is torn) may be strongerthan those fibers at the very edge. In such a case the result wouldbe a rising curve and the peak would not represent the initial tearbut the tearing strength of the fibers near the edge, or halfway be-tween two slits of the paper. The nonrecording type consists of abeam balancing on a knife edge (the two arms of the beam being equal).One end of the beam holds a 300-cc. glass into which water as the loadmay be poured from a 500-cc. burette until the paper tears. At theother end of the beam one half of one slitted end of the test sampleis clamped; the other half and the other end of the test sample areclamped against a vertical plate opposite. A special die is used forcutting a slit and eyelct hole at each end of the middle of the testsample. The force at the tearing end of the beam is equal to the

weight of water in the glass. This instrument gives merely the mnxirmatearing strength of the paper. The error caused by the bean positionand that resulting front the impact of the water are discussed. It isbelieved that the second instrument will give results within a 5% erroron those -mority of papers. Because butter comparative results arcobtained by tearing paper in the machine direction, it would socn thatall tearing tests should be nade in this direction. 3Further, because

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682. Houston, Paul L. A supplementary study of-oormercial in- --struirits for determining the tcoring strength of paper. Paper Trade J.74, no. 10:43-46(March 9, 1922); C. A. 16:4059.

-Supplementing the work reported in Technologic Paper rNo. 194 of theBureau of Standards, a study has been nade of the Elr-ndorf tearingstrength tester. A brief description is given of the instrument' and aformula is developed for the calculation of the tearing strength, andalso for the calibration of the instrument. Tho particular instrumentstudied was found to be graduated correctly. Tests indicated that thorewas a slight variation in friction in the ball bearing which mightresult front imperfect balls. However, any error that night be causedby slight variations in friction in ball bearing or indicator sleevewould be too small to be considered in cn instrument of this type,which is not a precision instrunont. Tests with writing and bag papersindicated that check readings could not be obtained by using differentplies; 1 to 32 plies wero studied. It would seem necessary to reconmondthe number of plies to be used for certain grades and weights of papor.The manufacturer has rocomncnded that readings be taken between 10 and

'20 on the scale; this ranie is small enough to allow the use of notnoro than two different numbers of plies. In the case of some papers(ledger in this study) both one and two plies gave readings between10 and 20. The tests with the majority of the papers showed that oneply gavo higher results than the other plies. Therefore, it night bewell to eliminate the use of one ply where it is possible, oven thoughit should give an initial reading between 10 and 20. It is concludedthat the instrument is built on sound principles of mechanics, is cali-brated correctly, and will perform satisfactorily provided certainrccornondation- are made mandatory.

683. Improved Elnondorl' paper tester, with a sinplo moisturecontent indicator. Paper 28, no. 10:16-17(l(oy 11, 1921); Pulp PaporMag. Canada 20, no. !6:326(April 20, 1922).

Thc inprDvermnt appears to be the addition of a knife for cuttingthl slit which starts the tear after the specimen is in place. A simplemoisture content indicator has boon devised front which the percentageof contained moisture nay be read. This consists of a balance, graduatedto read from 0 to 20; comparison of the sample is made with a shoot ofknown moisture content . Data are given showing that at noisturc contentsof 0, o.06; 0.10, 0.13, and 0.16%, tihe tec-?ing strength of a bond paperwas 60, 76, 88, 96, and 105 grams, respectively. With a kraft paperof moisture content of 0, 0.066, 0.09, and 0.15, the values were 300,400, 416, and 500 grams.

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- Tearing Strength

684. Institute of Paper Chemistry. Tearing strength of paperPaper Trade J. 118, no. 5:13-16, 18-19(Feb. 3, 1944); B. I. P. C. 1

- - Elmendorf's method f- testing- paper for tearing strength satisa long-felt need in a very simple and effective manner. However, sthe advent of this satisfactory method for-measuring tearing strongmany data on this property have been obtained which ore not well unstood. Many practical facts regarding the behavior of tearing streare known, such as: the negative correlation between tear and tensiburst; the usefulness of tear in controlling beating and other rofias regards cutting,'when considered in conjunction with tensile orbursting strength; similarly, the usefulness of tear in comparing dtypes of beating actions. Very little work appears in the litcratuthe theory of tearing strength. If a theory is to be useful and coprchensive, it must account for such facts as: tho'variation of teastrength with degree of beating (slight initial rise to a narrow mafollowed by a decline); the dependence of tearing strength on fiberlength (positive correlation); the increase in tearing strength accing a decrease in bonding strength brought about through the use ofadded to the furnish, and the inverse effect. A new theory is prosby means of which a careful analysis is made of the manner in whichenergy expended in tearing a sheet is dissipated in the paper. Whoshoot is torn, _m fibers are ruptured in tensile failure and n fiberpulled intact from the mesh of contiguous fibers. The average workquired to break a fiber is ordinarily insignificant in comparison Vthe work required to pull a fiber intact from the mosh, the force ivolved .in the latter case being somewhat loss. Since the average tforce is equal to the sun of these two works divided by twice the 1of line of tear, discussion of tearing phenomena with theory reduceto consideration of the effects of various treatments and pulp propon (a) the relative numbers of fibers ruptured in tension and pulleintact from the fiber amesh, and (b) the average work required to pufiber from the mush. The initial rise in the tearing strongth-boottime curve is due to the fact that, in the initial stages of beootithe "frictional drag work" increases by virtue of tighter onmnshmorcaused by clightly"incrcased bonding, during which timo only 6 ncglnumber of-fibers fail in tensile rupture. As"thc boating continueshowever, more fibers fail in tensile rupture and, therefore, fewerarc pulled intact from the ncah. Since the frictional drag work pcfiber is very nuch greater than the rupture work, this decrease in.number of fibers pulled intact from the mnosh causes the tearing atrto decrease. Similarly, the addition of a matcriol which reduces Istrength will increase the tearing strength by increasing the nunbcfibers pullcd intact from the sheet, and it is frequently observedthe addition of a bonding agent will ccuse a decrease in tearing st

, ,. The positive correlation between tearing strength and fiber lengthduo to the fact that the frictional drag work depends directly on taverage fiber length, boing theoretically proportional to this lengThc Elmondorf-Thwing inotrunent is based on a uniquely simple, atrtforward, and intrinsicolly accurate method. Excepting certain obvJmnladjuotnonta which could be noted by any observant operator, this

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checked and calibrated. A theoretical error arising in the manner ofallowing for friction in the pointer mechanism and bearing has been - -studied,- and-lt is shown that this is-of io-real significance, provided,of course, that the pointer stop adjustment is properly made. An errordue to multiplicity of specimens simultaneously tested is brieflydescribed.

685. Institute of Paper Chemistry. The Thwing initial tear tester.Paper Trado J. 113, no. 4:21-26(July 24, 19111l); B. I. P. C. 11:457.

The Thwing initial tear tester was designed to measure the forcerequired to start a toar on the edge of a specimen, which approximatesa failure frequently appearing under use conditions. From a considera-tion of the mechanics involved, a tear should be caused by a force whichis pure shear. In other words, the forces acting on the specimen at thepoint of rupture should be perpendicular to the surface, resulting ina compression on one side of the sample and an opposed compression onthe other side. In testing a specimen, such as heavy paper or lightboard, the stiffness of the specimen is not sufficient to result in pureshear, so that some tension will be set up in the sample. The fartherapart the jows holding the specimen, the greater will be the tensileresultant of the force applied. Under such conditions, the test becomesmoro of an edge tensile than an initial tear. The Thwing initial teartcstor has two jaws, each with a surface 3/4 by 2 1/2 inches, mountedone inch apart on horizontal shafts hold in a rigid supporting framework.The jaws are so mounted that their surfaces are horizontal and one edgelies along the center line of the shafts. The back of each jaw is threefourths of an inch from this center line, allowing spcciricns to beinserted accurately before applying pressure by moans of the tighteningnute. A ratchet is attached to tile shaft supporting the rear jaw, anda crank and paDwl mechanism is provided to act upon this ratchet. Intho starting position, a nctal pin on the ratchet rests on the framework.Tho shaft carrying the other jaw supports a weighted pendulum and isconnected by mcans of goars to a noodlo mounted on a dial at the frontof the instrunont. Those gears amplify the notion of the pondulun sothat the noodle travels through a greater arc than that through whichthe pondulur- passes. Riding on a small shaft of the gcar assemblybehind the dial is a strip of spring nctal which, through friction,holds the needle in any given position. A stop engages the pendulumin n vcrbiccl position before each test, allowing the noodle to bereturned to the zero reading. The specinmn to be tested is clampedfirmly in the joaws. The pendulum stop is released, and tho crank is turned at a uniform speed, causing the roar jaw to rotate. Throughthe co-nroctjng test strip, the front clamp and the pendulum rco alsocaused to rotate. The indicating noodle moves until at the instantof fi:Lure, the pendulum recedes toward the vertical position, thencodlo rencining at the position of naximn-n displacement. A readingis taken, the ratchet returned to the starting position, the stop'insortod in tho pendulum, and the needle moved back to tho zero mark.Thc following conclusions aro drawn front a study of this I[nstumcnt:


The Thving initial tear tester gives reproducible results. The nagnitud - - -of the results, in general, is incroased'by increasing the width of thespecitridn. Within reasonable linito, the rate of loading does not appearto hare -a significant effect on the results. Inconsistent results 'areobtained by testing several strips sirnltancously. Initial tearing strengthcorrelates in a general way with Elnondorf tearing strength and withtensile strength. Initial tearing strength ns determined by the subjectncthod is largcly dependent upon tensile strength and stretch, the natureof the depcndcncc being such that an increase in tensile strength and/orstretch causes an increase in initial tearing strength. The followingchanngs arc recommended. (1) The adoption of a means of loading at amore uniform rate. (2) The calibration of the dial in terns of actualpounds of force exerted on the specimen. (3) The installation of awing-tipped pointer on the dial to reduce error in reading the scale.(4) The provision of variable pendulum weights with corresponding dialcalibrations to zepand the ronge of the instrument to cover lirhtor andheavier materials than those covered by the present range. (5) Thedesign of supporting rmebero so rigid as to ensure constancy of separa-tion of the two pairs of jaws.

686. Jacobsen, P. M. H. Paper texture. Wochbl. Papierfabr. 56,no. 46:1398(3,ov. 14, 1925); T. S. 82:501.

The ratios of the breaking length of paper samples with and acrossmachine direction are given for strips-of length 0, 1, 2, 5,'and 180 mm.;the values for a kraft wrapping paper are 0.55, 0.57, 0.57, 0.56, and0.53. The percentage adhesion is defined as the breaking length with180 cc. free length divided by that at 0 m. times 100.

687. Jacobsen, P. M. B. Strength tests on paper. Papier-Fabr.23, no. 45:717-718(iTov. 8, 1925); Wochbbl. Papicrfabr. 56, no. 48:!54'-1456(Nov. 28, 1925); T. S. 82:301; 83:52.

The so-called zero breaking length (at 0 mm. free length) of paperrapidly increases at the beginning of the beating process and thenslowly decreases. Possible reasons for this are discussed.

688. Johnnsson, David. Testing methods for chemical and mechani-cal pulps. Svensk Papperstidn. 40, no. 9:210-21 8 (.May 15, 1937);Zellstoff u. Papicr 17, no. 7:286-289; no. 9:389-392; no. 10:436-458(July, Sent., Oct., 1937); B. I. P. C. 7:359; C. A. 31:4812; B. C. A.1937B:1321; T. S. 106:91, 94.

A comparison between the values of the Thwing-Elmondorf, the-Iarx-Elmendorf and the Brecht-Inoct instruments for determining the

tear-through strengths of papers has been carried out at Ocstrand.For beaten papers, the instruments are of equal value; for unbeatensanplos, the Thwing-Flmondorf values ore considerably higher. TheBrocht-Imact apparatus permits accurate testing with a single paper.hcet.

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.-. ...... Tearing Strength 247

6S9 . Mallett, E., and Marx, R. The calibration of the Eimendorftearing tustor. Proc. Tcch. Section, Papernakors' Assoc. Gt. BritainIreland 4,_part 2:212-222(March, 1924);C.. A. 18:1907; T.-S.-79:219.

The initial step is to determine the first moment of the pendulumor sector about-its axis; the next -stopis to determine tho dffoct offriction in the instrument and the low which it follows. The -differencein the angle at the conclusion of various half swings was found to bedue to energy becoming stored in the pointer. The method of graduatingthe sector is outlined. The operation of the instrument dependsprimarily on the tine period of the sector when swinging freely andthe friction of the pointer. It is therefore possible to formulatethe following two conclusive tests for its correct operation which aresufficiently accurate for all practical purposes: (1) The sector whenallowed to swing freely from its initial position should nake notless than 180 complete swings before coning to rest. (2) The sectorwhen allowed to swing fron its initial position but with the pointerheld securely against the stop should nake not loss than 12 conploteswings before coning to rest.

690. Marx, R. J. A new tearing tester. Paper Makers' Mo. J. 59,no. 4:151-154(April 15, 1921); World's Papor Trade Rev. 75, no. 2:172,174(Jan. 14, 1921); Zollstoff u. Papier 2, no. 2:35(Feb., 1922);C. A. 15:2185.

A brief description is given of the principle of the Elnendorftester as modified by Marx.

691. Nagl, Hans. A study of the nochanisn of the rfllnondorf tearingtcet. Pnpior-Fobr. 27, no. 27:421-424(July 7, 1929); C. A. 23:5589.

Th_ tearing test is especially valuable in showing the oxtunt towhich the fibers have bococr shortened in processing. The sanm pulpboaton t- S0 dogreos Schopper slowness in bcaters- with store and withiron tacklo gave, respectively, 190 and 111 grams tear. In sgncralt$c1ic strength and tear vary inversely. Calondering docreascs thetear, whereas normal moisture variations have no definite effects.iTh basis weight and the number and width of the strips torn affectthe results. Data are given to substantiate those conclusions.

692. National Association of Purchasing Agonts, Inc. Corrugatedfibreboard shipping containers. No. 19, 1934. 8 p.

Tcarin, Strength (Elnondorf) Toot. This test is only applicableto individual shots of lincrboord and corrugating nediun and to piecesof unused tape. Tost specineon should be cut from unwrinklod, uncrcased,and unblemished stock, four each with the grain running the long artshort way of the specimens (in the case of cloth tape, the long or thecross throads-). The spocimons shall be not less than 6.3 cn. (2.5inchcs) in length (on sanplos cut along the cross tircoads of two-incl

-. E: tape such lornth is acceptable) and of such width that the distancefrom the apex of the starting cut to the top edge of the specimen inposition in the tester shall be exactly 4.3 cn. (1.69 inches). The

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Tearing Strength '248

specimen shall-be placed in the Jaws of the tester with the bott-o cdgerooting upon the bottom plates and so that not loss than 2.5 cn. (1.0inch) of the specimen extends into the novable jaws, the initial slitnade, and the pendulum arc released tearing the specimen. Tests inwhich the tear deviates noro than 6.3 rn. (0.25 inch) from the lineof the initial cut shall be disregardd. -The tcaring-strongth- shall becalculated in grams by multiplying the readings on the inotrunent by 16.Not more than one of the four tests in each direction nay fall below thespecification, with- the-average of the four teots meeting the requirement,for conpliancc. Howovcr, if the initial tests'in either or both direc-tions fall to comply, a series of 12 re-tests of either or both (accord-ing to tho'failurc) shall'be node, of which not more than three tests nayfall below, with the average of all 12 tests complying with the speci-fication, for acceptance.

693. New tearing machine measures strength of paper. Paper 26,no. 26:11(Sopt. 1, 1920); C. A. 14:3319.

The samples of paper to be tested are about 5 inches square and twoparallel cuts, about 1.5 inches deep and about 2.5 inches apart,. are nodeon one edge. The resulting center tongue is then turned up at rightangles and the paper is clamped to, the base of the machine with thetongue projecting vertically along the side of the flat metal clamp.The tongue is then gripped by means of the '"vor Handy" letter clip,front which a wire rnus up over the wheel. The counter weight on theother end of the wire balances the weight of the clip. The wheel, whichis graduated in dogrcos, is mounted upon a ball-bearing bicycle wheelhub and a lever is connected to the near side of the shaft. This lever,which is much in the nature of a pendulum, is provided with an adjustableweight. When the pendulum is released, it swings downward, carrying withit the wheel and the wire, thus pulling the letter clip upward andtearing the sheets of paper. This is an early forn of the Elnondorfteeter.

694. Ncw tearing tester. Paper Trade J. 83, no. 26:40(Doc. 23,1926); T. S. 05:162.

The Thwing tearing tester consists of a support front which issuspended a pondulun that swings on a ball bearing. On the rilit armis a clamping joer. On the supporting frame is a similar jaw, at thesane level as the one on the pendulum armt, when the latter is in Craised position. 'The paper to be torn is inserted into these jaws and,to start the tear, a slit is node in the paper by raising a knifo edgewhich is attached to the franc. The ponduluw, when released front itsraised'position by lifting a simple catch, tears the paper until theresistance offered by the tearing paper bring the pendulum to rest.This resistance is designated in grarn on a large dial, by a needlepointer which is actuated by a pinion in ncah with a larger gearwhecl which rotates with the swing of the pendulum. The needlepointer travels almost completely around an 8-inch dial, for thefull swing of the pendulum, making the scale reading very accurate.The most valuable characteristic that the machine has is its oscsi-tivoncso in tearing one sheet of paper at a tiio, whether tissue orledger, thus allowing the paper to tear as naturally as when tornbetween the fingers, in which case nore than one sheet is never torn todetorninc tearing quality.;

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695, Nichols, Lorrel BU. S. patent 1,989,625 (Jan.

A test strip of paperi.. apart along its straight fre

in shape with their centersincreasing tensile stress ispaper between the centers oftakes place; the centers andor permitting the secured oroubotantially uniform rate.recording the tensile stress

i. Apparatus for determining tearing strength.29, 1935); T. S. 101:238.

o secured at two areas,- whch are spacede edge and which are preferably semi-circularat the free edge of the paper;-progressivelyapplied along the marginal edge of thethe secured areas until initial tearing/or torn edge arc then separated by causingoes to rotate about their centers at aMoans are provided for measuring and

as applied throughout the operation.

696. Oliver, Cyril V. Variability in results- rt with in paper strengthtesting. World's Paper Trado Rev. 93, no. 8:660, 662, 714; no. 9:754,756, 758, 796, 798; discussion, no. 11:938, 940, 942, 994, 996, 998(Feb. 21, 28, March 14, 1930); Paper Makers' Mo. J. 68, no. 3:103-109(March, 1930); Paper-Maker 79, no. 6:595, 597, 599-605(Juno, 1930);Proc. Tech. Section, Papor Makers' Assoc. Gt. Britain Ireland 11,port 1:53-74; diocuosion, 74-84(0ct., 1930); B. C. A. 1931B:582; C. A.24:3366, 5484; T. S. 92:157.

The Morx-Elmondorf tearing tester was studied. One disadvantage ofthe tearing test is the fact that some papers "skin" during th' test; thisis especially true of thick papers. Another point about the tearingtester is the fairly frequent alteration of the zero; in two sets of50 tears, the zero altered four times in one set and three times in theother and the maximum alteration was two points on the actual graduations,or an error of about 7% on one of the sats of results. In those teststhe average toar was 57.8 and 30.3; maximum deviation 5.2 and 7.25%,average deviation 1.6 and 3.4%; maximum zero alteration 2 in each case;tooar which okiuicd 24 and 15%. The result of tearing two shots ofa paper together is not always double the single sheet tear. Resultsprove that the tearing tester is more accurate when the reading registersabove 20 or o-er than -hen it is 10 or under. If four or more shootsare torn together, very consistent results are obtained (data for 1 to10 shotss. Readings above 70 arc not very reliable. The one largevariable in the tearing tester is the pointer.

697. Paper Makers' Association of Great Britain & Ireland. TechnicalSection. PoarE Testing Committee. First report; London, The Associa-tion, 1937. 85 p. Also issued, with discussion, as Vol. 18, part 1A, of theProceedings of the Technical Section. Soo also World's Paper Trade Rev.,Tech. Convontion No., March, 1937:4-72; B. I. P. C. 7:350.

Specifications are given for the tearing test, using the Marx-Elmondorf tester. Those include the preparation and dimensions of thetest oamplo, the checkinn and adjustment of apparatus, and the- operationof the instrument. The tearing test is most significant for those paperswhich, in actual use, are subjected normally to folding and twisting andin which the rupturing forces involved are relatively small and arc notvcry variable; these include cigarette papers, waxed tissues, envelope

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699. Poultor, A. C. An initial tear tester. Patra J. 8, no. 1:.14-22(Aug., 19,4); B. I. P. C. 15:103.

--A-clothod is deocribed-for-adopting the Schoppor tensile tester toanouiro the initial tearing resistance of paper, boards, and film.

The Marx-Elmordorf and the Thving-Elmcndorf testers measuro the forcc-rcluired to continue a tear which has already been started in the material*under test; this is usually termed the tearing resistance but shouldproperly be called the internal tearing resistance. These instrumentsdo not reproduce the condition when the break or tear starts from theedge of tile shct. The ratio of the initial to the internal tearingresistance is not constant for different materials but varies withthe extenaibility and structure. The Schoppor tester (selected be-cause the pendulum system can be used to record the tearing resistance)has boon modified by the addition of a clamping unit to act as aninitial tear tester. aro clamps are used; the left-hand clanp isfixed to the base of the unit, whereas the other is mounted on ballraces and is free to rotate about an axis along the front edge of theclamps. Details are given of the method of operation of the instrumentand of carrying out the test. The fixed clamp can be adjusted to givedistances of 1/iO, 1/4, 1/2 and 1 inch between tho clamps. The depthof the paper held in. the clamp can be adjusted to 1/4, 1/2, or 3/4 inchby positioning pins. Friction in the clamp bearing is compensated bysetting the pendulum zero for each range. The force measured is notsimply rlatoed to a fundamental property of the nmatcrial but dependsupon its tensile strength, extensibility, and rigidity, and alsoupon the distance between the clamps and depth of material clamped.Although increase in the distance between the clamps has the sane generaleffect on all natoriola tested, the magnitude varies so that testsmade witl a i/10-inch spacing nay grade the materials in a differentorder from those rmado with a l-inch spacing. The sacm is true of thedepth of rmtcericl in the clamp. Over the practical range of the in-struniont, the tcorirp resistance is independent of the rate of tearing.This test is empirical and the results depend upon the test conditions.Data are given Cfor cotton fabric, vegetable parchmenont, filter paper,and several plastic films.

700. 'Rcnniclcs, Norbert G. Mbnufacturc'of paperboard. Chicago,Fibre Containars, 1939. 47 p. Chapter on paperboard tooting in FibreContainers 24, no. 9:20, 22, 24, 26, 28, 30(Sopt., 1939).

Tearing streonth. The Elnendorf tester is used. This test io appli-cable to individual heots of paperboard. Samples nust not be loss than2.5 inches in length. The width of the sample nay be explained by sayingthat an initial or starting cut is nade in the sample, and the widthnust be such that the apcx of the starting cut is exactly 1.69 inchesfrom the opposite sido of the sample. The spocincn is placed in the jawsof the toestcr with the bottom cto resting upon. the bottom plates, sothat not less than 1 inch of the specimen extends into the movablejaws. The initial slit is then made and the pondulun arc released whichtoars the sanmlo. Testo are ignored in which the tear deviates morothan 1/4 inch front the line of the initial cut.

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701. Rieth, I. Strength determination. Papier-Fabr. 27, no. 45:693-6941Nov. 10, 1929); T. S. 91:205. .

_.--_ _- - Thc-rclativo-huidifty, -upon vhich the noisturc content of the.- - . -- . papor is dependent, is of groat importance in papor tosting. -- In passing -

fron 5.8 to 9.? 1%oisturo content therc-i-a-diffoernco of 25% in -..- -. - -- -- the tearini strength.. -

702. Sanmot, Charles F. New tearing tester.. Paper Trade J. 83,.| ' -no. 2T:40(Doc. 23, 1926); T. S. 85:162.

A brief illustrated description is given of the instrument builtby the Thwing Instruncnt Co., consisting of a support fron which issuspended a pcndulun that swings on a boll bearing. On the right armof the pendulum is a clamping jaw and on the supporting franc is asimilar jaw at the sane level as the one on the pendulum arm whenthe latter is in a, raised position. The paper to be torn is inocrtodinto those jaws and then to start the tear, a slit is rado in thepaper by raising the knife edge which is attached to the froac. Thencchanisr. is oxtrcmcly siriple and sensitive to slight differences inthe tearing strength of the paper. It con bo used equally well fortesting tissues or ledgers and a single shcct can be.used for the testin either case.

703. SaOmlot, Charles. Testing tearing resistance of paper. Paper25, no. 22:17-l8(Fob. 4, 1920); J. Sec. Chcn. Ind. 39:330A; C. A. 14:1217.

The instruiont used was a Trodificd Schoppcr tensilt strength tester.The toot as a-ppliod is to allow the lover arm to owing from a definiteraised position after there is clamped betwoon the jaws a piocc of paper,so slit that one end fastens to the upper and the adjacent ord in thelower' jaw, and the strip is brought to a tout condition by the handwhcel, tearinG it slightly--n distance of about 1/8 inch. The loverarm is then released front its fixed position and the resistnnc in tearingoffcrcd by the paper prevents the arm from falling its total: distance,nakiDn it cono to rest at that point on the scale wherc the tceringresistance balances the force of the. falling arm. A wooden arm wassubstituted for the mntal arm of the machine and waa so weighted that,when it is allowed to fall from the 30 nark, it will swing to rest atzero on the scale. The method of calibration is indicated. Resultsore given for 100% rag bond, artificial parchncnt, M. F. printinG,Manila wrapper, Icraft wrapper, and newsprint. An avcrage of 5 testswill g'ivo a practical working value and, for more accuracy, 10 or moretests nay be averaged.

704. Satact, Charles F. Tcaring tester. U. S. patent 1,447,185(March 6, 1923); Pulp Paper Mag. Canada 22:62°.

The invention consists of two jaws for grippinG tho papor, onebeing fixed to the frano and the other to a movable clement (preferablyin the forLi of a weighted swinging lover) which moves under the actionof g-ravity until the resistance offered by the paper to tearing, balances

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the pull of 6-rovity. Throe forms of instrument embodying the principleare doscribcO.. In each one the two portions of the paper remain inthe cane plone during toorina, thus ensuring equal tensiontltbacuhoutt

--- tho- operation. - T126 thlcory of the Instrument is outlined. The scalecan be Graduated to give the tearingj resistance directly in grams- -The range of the instrunolnt can be mado to embraco papers havingeithlcr hic~ or low tearingI resistance by chalL~inCr the weight or byadjuatin3: its position on the lower era.

7- Ctt HCrfry L. New toorina strength tooter. Paper 29,no. 99" -412ott'2 1921). .

The wall-Imowun theory of the slidinC or rallied-, weigt upon. aninclined plane is the basis of thle Invention and by this novel design~all difficulties encountered through machine design and constructionin other models have boon overcomIe. An Iron base nupportitiU twoside franca contains the entire mchanism. Twro bearings mounted uponthe top of the side frames carry a walking boom or inclineablo plansupon which root two round voichto connected together by a ball-boarinccarrinac. Fastened to a cross bar in this carringne is a chain whichpaseo over n screw and Is adjustoble for different lon~ths of thespecimen. The inclined plane is operated by slidine across hands on

A either aide which In turn arc lowered by maons of'o vertical screw: upon which a worn Goarp acting as a nut, revolves. The worn drivine3

this gear is operated by a train. of change ,-csrs driven from thenochanion below. 'ihe machine is fitted with a chart, the verticallines &cnotinc, strength and the horizontal lines Otretch., The chartTroves horizontally from right to loft and the pon, supported from therider on the scale, moves upward as the specimen clon~atco. Ad-vnn-togas of this typo of tooter arc pointed out.

706. Sol Ius, N., and 1,audonbak, W. Mechanical stron~th of paperin relation to- the composition quality and degree of boatine of thep -~ Tsonlu~ol Nauch.-Ioalcdovatcl. Inot. uoh rn ncil1934, no. 4:2~3-265; C. A. 29:7650.

The tcnrlnnS stron.,,th of paper produced fron a mixture of chLenicaland nechanical pulps depends on the tcerinC strength of the twocomponent pulpc.. It is ;lossible to clccrease tho contents of chemicoliulp in the compositiono of paper without impoiring its n~charnicolpro-portics by o. Horo cfficient boating of the chemical pulp or by

'in. :proving the quality of the mechanical Tralp.

1. osifications for white, unbleached, and colored Papcrsfor railroad ;7rintings and writings. Papaterio 56, no. 21:1118,1121-1122(Nov- 10, 1934); B. I. P. C. 5:1-57.

The official method for &otcrr1JninC the breaking loagth is -ivan.

708. Ouornoistr, Erwin. The Elmondorf tearing test anrd itsrelation to the burotinjn test. Paper Indl. 5, no. 3:477-479(june) 1923);C. A. 17:2645; T. S. 77:161.

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710. Szoeko, P.,, and.Fraonkol, 0. Tearing strength and stretch.Papier-Fabr. 33, no. 25:213-214(June 23, 1935); B. I. P. C. 6:578;T. S. 103:192.

- With reference to an earlier study by Reito, the authors showthat neither tearing strength nor elongation stretchh) -alono-definesthc quality of b paportor its-resistanco to nechanical stresses,but that both factors are required for determining those properties.They illustrate their theory by grapha and equations.

711. TAPPI. Internal tearing resistance of paper. TAPPI StandardT 414 n-42. 1 sheet. Paper Trade J. 84, no. 4 : 4 9-50(Jan. 27, 1927);86, no. 8:209, 211(Fob. 23, 1928); 94, no. 18:43(May 5, 1932); Tech.Assoc. Papers 15:162(June, 1932).

This method is adapted for detorining the overage force in gransrequired to tear a single sheet of paper after the tear has beenstarted. This is distinguished fron the initial or cdge tearing re-sistanco. The Thwing-Elnondorf teotor is used.

712. TAPPI. Connittcee on Paper Testing. [Tearing test. PaperTrade J. 75, no. 4:4 7-48(July 27, 1922).

Includes the Knife edcg nothod developed by A. D. Little, Inc.,the Withan and Case testers, the Schoppor tester and the Elnendorftoster.

713. Toating tearin g strength. Paper Ind. 2, no. 9:1393, 1438,1440 (Ioc., 1920).

This is a reply to the article by Elnendorf which appeared inthe J and ust is s of this Journal, in ohich the author dis-acgrocs with the viewpoint that the tearing strength is the nost in-portant Droporty of wrapping and bag papers. It is pointed out thatthe consumer of paper is norc interested in the initial tear thanin thc continuance of that tear.

714. Thing, Charles B. 'Initial tear testing apparatus. U. S.patent .,364,388 (Oct. 25, 1932); T. S. 97:222. Cf. Instrunonts 7: 168(Aug., 1934).

The instrunont is designed to give on accurate indication of thetorsiono- strain applied to paper or cardboard at the nooant of initialtear. The construction is such thathe e graduations of the scale arcspaced so as to provide larger spaces at those portions at whichinitial tear ordinarily occurs, and the indication of the pointer onthe scale is maintained after recession of the drive shaft duringthe tearing operation.

715. Thwing Instrunmnt Co. Tearing tester. Mclliandi Toxtilbor.2, no. 7:985-986(1930); J. Textile Inst. 22:A203.

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This apparatus, known as the EImendorf tearing teter, has beendeveloped for the paper industry and is used to measure and indicatein grams the resistance to tearing of fabricated materials. Anattachment to augment the capacity of the apparatus, so-that it vlllaccommodate stronger materials, has recently been perfected. Itmeasures the actual work done in effecting a tear; the personal --element does not come into play and-no calculations are required.

- --- tIts chief structural details are described and illustrated.

716. Tachudi, H. The Elrendorf tearing apparatus. Wochbl.Papierfabr. 57, no. 35:964-965(Aug. 28, 1926); T. S. 84:278.

A brief description is given of the Elmendorf tearing testerand its theory. This does not give values comparable with theSchoppor apparatus, because the latter gives a mininum value with astrip 18 cm.' wide.

?717 . U. S. National Bureau of Standards. The testing of paper.Washington, Govt. Print. Off., Feb. 12, 1921. 37 p. Circular No.107.

A brief description (page 18-20) of a modified tensile testingmachine, in which the weights have been removed to give it more sen-sitivonoss.

718. Wallin, S. Tearing strength of paper. Svensk Poppcrstidn.24, no. 18:356-357(Sept. 30, 1921); C. A. 16:645; T. S. 75:206.

A hook is substituted for the pan of the balance and the tearingis accomplished by adding weights to the other pan. The authorsuggests the concept "tor surface, " meaning the surface of the paperbeirg tested whose weight is the same as the force needed to tearthe paper. Ho also suggests "longitudinal tear surface, " crosstear surfacc," and "average tear surface." It is more difficult toobtain accurate figures for cross tearing than for longitudinaltearing.

.7j9. oells, Sidney D. Report of the Paper Testing Committeeon the tearing test of paper. Paper Trade J. 76, no. 26:49-54(June 28,1923); Tech. Assoc. Papers 6:102-106(1923); World's Paper Trade Rev.80, no. 5:416(Aug. 3, 1923); T. S. 77:161.

Bosults obtained by 16 testing stations (14 with Elmendorf,1 with Withan, and 1 with Eastern Manufacturing Co. testers) on 12sets of sanploe arc tabulated. Tlle factors influencing the testsseem to be related more to variations in the paper than in the in-.trumonts. WVhorecvr more than two sheets wore tooted, the results

,·B ~ checked very closely and a deviation from the average of more than' -'10~% vm exceptional. The ncan deviation is usually less than 5%,S'~ indicating the reguJority of the instrument. The fact that the mean

deviation for the station averages usually greatly exceeded the meanvariation of the individual tests would indicate variations in theinstruments or in their setup or operation. The following causes

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723. Williams, F. M. Resistance to tear and the measurementof surface friction or slip of paper. Paper Trade J. 114, no. 15:16-17(April 9,1942);C. A. 36:3356. ..

The instrument is of the pendulum type and consists of a rovolv-ing drum mounted on ball bearings with- a suitable stand, withaccurately counterbalanced pointer not rigidly attached to the drumbut moved forward by contact with a pin projecting from the back ofthe drum. The load is applied through a similar revolving drumdirectly attached to a motor, which through a reducing gear appliesload at the rate of 1 r.p.m. The two ends of the sample (1 inch wide)are attached to the revolving drums by placing the sample in slotsand folding over ends by means of a spring clip arrangement, whichholds the sample firmly in place. The load is applied by a pressingswitch; as th pendulumm weight rises, the noodle is moved forward overa graduated scale intil tearing takes place. This reading may betaken as initial tear, but the test may be continued to determine thc.presence of hard spots which will advance th' noodle slightly further.This nosureos the tearing resistance of the sample in grams direct pulland not by the indirect method of indicating the absorbed energy of afalling weight. The results obtained are somewhat lower than withthe conventional method of measuring tear. However, when this direct-weight method is checked by lifting a known dead-weight attached toone end of a slitted sample, the results indicate that tear testsmeasured by the direct method, although lower, give a more accurateindication of actual tearing resistance, because the other methods ofmeasuring tear involve a certain amount of tensile strain as wellas pure tearing resistance.

724. Winterbottom, Marion, and Minor, Jessie E. rlic test fortearing resistance. Paper Ind. 18, no. ll:928-930(Feb., 1937);B. I. P. C. 7:234; 0. A. 31:3268; B. C. A. 1937B:770; T. S. 105:371.

The number of sheets torn at one time in an Elmondorf tearingtester has an effect on the final results. The instructions "enoughshooeets shall be torn at one time so that the reading on the scaleshall be not less than 20 grams nor more than 40 grams" provide a toolarge working range. A modification is suggested to read that alltests shall preferably be made on single samples, except in thosecases where such values are too low for accuracy. In no case shouldsheets be doubled to give a value of over 30 on the scale.

M72. Within, George S., Sr. Paper tester. U. S. patent 1,298,138(March 25, 1919); Paper 24, no. 5:22-23, 40(April 9, 1919).

A ppoer' tester comprises noons for supporting a trip of papcr,means for fastening one side of one end of the strip to the support,a weighted lover provided winh means on one side of its fulcra 'forengaging the other side of the paper, mneoans for adding weights tothe opposite side of the lever, and neons for indicating the forcerequired to perform the tearing operation.

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direct tensile stresses. In thle casa OfPrinting papers, tensilestrenztbl neasv"rements indicate the potential reoistanc0 to breakingwhen subjected to strains during travel from the roll through the webPreos nechatsno In the process of printing. In general, totiil~e strengthtests ':rate n~Pers in -the sma order as the burstinge otrengh tests,sthich,' deo&pz 3t es~ladsrtch. OMo advantage off tensilestoc-h over bursting strength is that the st-eng~th Of' tile shoot inthe tesef )n test can-be lnees'red and reporte-d for each direction.,thereby d Etecting any nbnormal differences bet7,1cn the two direction1.In' mI control y-orlk the termi-le strength toot may be usdfod-termmingl the gone:'sl strength properties olf paper, but it is0 not noconvention, nor as rapid us -the bursting Stren~gth toot. Allth:ough thetonuil6. st,'r~ngth tost aoes not usually give such a good indicntiIon ofthe pi-ac icaj. 'Yitrenigthi" off parer as the bursting strength tent does,it fil.ls - -special need in the tooting of' paper subjected to tensilectrossec, _.22 Use.

72 - Anrther TC 5AnG Inntrrsaent Co.,Ic ThilrtothesrsCiro. No. 107. n~. ci..tsoo

T Veetpe or listed portable dial typo 269, bonchj dial type27'0, Pendulum benhal dial tYPe 271, and precicion mote driven 'type 250.~ypc 20 ed. 70 re Iustrotod. Type 271 la const:7ructd in accordanceto the TAPPI Standard P~ 404.

129. A-rcno~.t Albert, and Wathelot, Rnmanucl. Effect of' atmospherichumldity on the tensile strength of? writing and Dri-nting pano(rs._ Mon.pPapeterie belge 1-2:105, 1tO7-113(rcb., 1932); T. S. 95:77; C.A 26:5664;23 . P. C. 2:_326.

A gecnorol discussion of' the effect of hyd-rortetric conditions onthe break-Ing lenGth Of wrTitiwi and prir-ting papers.

Jj. Arneula; E. Strength and. rosictanco of' paper. Dreokinglength. Paplar 25, no. 5:209-2 12(i4ay, 1922); C, A. 16:3205; T. S.75:109.

A. discussion is given of the factors affecting the tensile strengthOf paper, off the. precautions to be token in. using -the Schiopz)rrteiltes~tor,.cand of. the strength tests to be applied to various ,radea off paper.7.Attainment of perhection in toting mochincr. World's PaperTrade -Bov. 1,22, no. 22:1.426, 14083(ncc. 1, 1939); 23. I. P. C. 10:2071.

1?sferenco is raido to the paper, testing mnchinec manufac Luared byGoodbrand and Co. for determininE the breaking strength anid elongationof allI classes of paper. The arparotus is described and. iflustrnted.

732. flaosbrg, A. The influence of' moiatur-e and tempsratm'e onlthe streng~th and, elasticity of paper. Panir-J. 21, no. ll:l05-i05;no0. 22:!14-12.7; no. l5:123-lP6; no. 14:i36.139(JUly 6, 25, 3.1, Aug. 11,1933); C. A. 28:318; n. i. P. C . 4:i6; T. S. 98:156.,

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Tensile Strength 262

Theories of paper strength are discussed. The strength of paperreaches a maximum at 50° C. and decreases with further heating. Ata constant temperature of 20° C. the maximum is attained at 1-2%moisture. At constant temperature elasticity is practically independentof the moisture ofthe papor.- When o-load-is applied in the-Schoppor itester, tle strip shows permanent elongation or slip before rupturing.This slip does not increase with time._ Paper heated for some time.

- - - at-100° C. will not recover its original moisture content. The higherthe heating temperature, the less moisture is reabsorbed. This per-manent loss of moisture is accompanied-by a permanent looss of strength.

733. Borcsi, Joseph G. New method of testing paper. Method oftesting and recording physical properties of paper and descriptionof machine invented by A. Retjo. Paper Trade J. 84, no. 7:39-42(Feb. 17, 1929); T. S. 85:141.

An instrument is described for making tensile and elongationtests and automatically registering the force-elongation diagram; thetechnique for its use, together with the precautions to be observedand the method of calculating the quality, is explained. A triangularrule has been devised for facilitating the measurement of the area ofthe diagram and the calculation of the quality of the paper.

734. Dosco tensile tester for paper. World's Paper Trade Rev.61, no. 19:912(±May 8, 1914).

testerThe Bosco / operates on a strip of paper rolled into a cylindrical

shell.' The two circular edges are fastened in two ring-shapedclamps, exactly concentric and located vertically above one another.If one of these clamps be turned slowly in one, the other just asslowly in the opposite direction, the paper is subjected to a torsionstrain, which is strongest in the center of the cylinder. The resultof this turning is a strain on the paper from every direction. Thedevice is so constructed (along the lines of the Schopper strengthtester) that the direction of revolution of the clamps can be reversedand the rotation in opposite directions is continued until the papertears. This figure comes very close to the power of the paper towithstand crumpling.

735. Breaking length. Wochbl. Papierfabr. 70, no. 21:454; no.27:603(May 27, July 8, 1939); B. I. P. C. 11:29.

Mean breaking lengths arc given as follow: Writing pbper ofbleached puln 50 to 100 grams per square motcr; wrapping paper of un-bleached pulp, glazed on one side, 13 to 100 grams; lkrft paper,either unglazed or glazed on one side, 40 to 100 grans. Average valuesfor writing papers range from 3000 to 5000 motors, for wrapping papers4000 to 6000 rcters and purc kraft papers 6000 to 7500 meters. Thetests were carried out vith a Schoppor tester at 65% relative humidity.

736. Brecht, W., and Blikstad, F. The tensile strength of paperperpendicular to the plano ol' the sheet. Papier-Fabr. 38, no. 8:50-51(Feb. 23, 1940); B. I. P. C. 10:347; C. A. 34:7603.

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Tensile strength is measured in either the machine or cross machinedirection of the paper' web but very little is knovn about this propertyin the third .ircction.--in the direction perpendicular to the planeof the chcct. Pcpt,-r· sarlJes, 20 mm. in diameter, were glued betweentwo wode._blocksl_Qf identical size and the adhesive -wrc allowed to---set for three houis3. ifte' this period, the blocks wore clamped ina Sciopper tensilc tcste r cnd the breaking strength wct dotormincd.-When the tr-o wDur-en blocks we're-glued together rithoulr, a paper'sheet in bc-trvcn, thc bocdiinC strength of the adhesive Wo sc gro at thatthe blocks cou d not be separated in the largest model for boardtesting witi a maxibvm breaking load of 150 Ikg. The tear alwaysoccurred, with..! the fibrous and never within the adhesive layers. Thestrength porgnndtcular to the plane of the sheet is always uxtremclylow. 0- the toon Esa3np1 tested blotting paper with values of 108,59 and 2.3 f'oa machine, cross machine, and perpendicular to plane of thesheet, and glassinc with 1090, 600 and 24 for the same direction repre-sented the lowest and highest values. Slack-sized papers from freepulps gave consistently lower strength figures than stronger and hard-sized papers from slow-boatcn pulps.

737. Coapbell, W. B. The tensile strength of single fibers.Forest Products Labs. Canada, Quarterly Rev. No. 2:70-71(April-June, 1950).

Following the technique of the Shirley Institute for measuringthe tensile strength of single cotton fibers, similar measurementswere nade on wood fibers. Difficulty was encountered in mounting thewood properly. Ruhloman (Paper Trade J. 82:168(April 1, 1926)) givesas the breaking load of wood fiber, around 13 grams.

738. Canadian Pulp and Paper Association. Technical Section.Tensile breaking strength of paper and paperboard. Official StandardTesting Method 10. July, 1942. 3 p.

This is practically the same as TAPPI Standard T 404 n-41.

739. Carson, F. T. Some notes on the revision of methods formeasuring the strength of paper. Paper Trade J. 102, no. 19:59-42(lny 7, 1935); Tech. Assoc. Papers 19:172-175(Juno, 1936); BritishPaper 4, no. 3:29-52(1936); C. A. 30:5034; B. I. P. C. 6:410; T. S.103:269.

A discussion is given of the proposed revision of the TAPPImethod under the headings: Dimensions of specimens, rate of testing,and report..

740. Clerk, Frederic C. Paper testing methods. New YorkTAPPI Publishing Corpn., 1920. 24 p.

Tensil strength is discussed on p. 15-16. The Schopper tester ismentioned. Relationship of other strength properties is illustrated.

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744. Costello, Coleman J. Comparison of tensile testers for paper..Tech. Assoc. Papers 7:68(June, 1924); Paper Trade J. 78, no. 15:189(April 10,1924); Paper 33, no. 26:136(April 17, 1924); T. S. 79:147; C. A. 18:1906.

Four machines were used. Two of these were of the inclineable balancetype, operated on the deadweight principle and best suited to test strips

... .. of-paper about 4 inches long and 1 inch-or-15-rm.-wide. A third machine was --hand-propelled and tested strips 1 inch wide and 4 inches long. The fourthmachine was best fitted to test strips of paper about 2 inches long and 15

- -am. vide; it was operated by a hcnd lever.- Twelvc lots of paper were tested,-the average of 10 tests being taken to determine the tensile strength of eachsample; duplicate tests wore made in each case; 1900 tests wero made in all.Considering the amount of variation between individual tests made on thesample, two of the machines gave results superior to those obtained with theother two. All four machines gave good results as regards comparisonofaverage obtained for duplicate tests on the same machine. That is, as re-gards duplicate determinations mado on the same machine, very close checksmay be obtained. When the average results obtained by the different machinesanr compared, however, there is quite a wide variation. This is duc, probably.not only to differences in the mechanical accuracy of the machines, but also'to differences in the size of the paper strip tested and the rate of theapplication of the load. It is apparent that tensile testers of differenttypcs cannot be used for strictly comparative results and therefore, in re-porting results of tensile tests, the kind of machine used should be specified.

745. Dalon, Gustav. A new strength tester for paper. Mitt. kgl.Material. 1911; Erga'nzhoft 2:12-22; Papior-Fabr. 10, no. 25:713-714(June 21, 1912); Papior-Ztg. 37, no. 39:1428(May 16, 1912); Paper 8,no. 10:17-18(Aug. 21, 1912); Wochbl. Papiorfabr. 43, no. 22:1894-1895(Juno 1, 1912); C. A. 6:2525.

The rapid paper tester is described. The strip to be toted is 50 m.i.(2 inches) long and 10 mmn. (3/8 inch) wide. The methods of testing thestrength scale, the expansion scale and the defects in the mechanical con-struction arc discussed. Tho values for the tearing length agree fairlywell with the larger apparatus (30 kg.) but the expansion values arc higher.

746. Doughty, R. H. The relation of shoot properties and fiber prop-crtics in paper. I. A qualitative study of the tensile strength-solidfraction relation. Tech. Assoc. Papers 14:243-248; discussion, 90-91(May,1931); Paper Trade J. 93, no. 2:39-44(July 9, 1931); T. S. 93:195; C. A.24:5022; B. C. A. 19323:718.

Tensile strength at rupture in p. s. i. of original cross sectionis calculated from thc breaking load on a sample of known dimensions.Solid fraction by volutnm is defined as the ratio of the volume of solidfiber in the sheet to the volume of the shoot. The value of fiber wascalculated from the sheet weight and an assumed density of 1.5 forfiber substance; the vblumo of the ahect was derived from its measureddimensions. The general procedure, was to prepare a number of shootsunder rigidly standardized conditions, employing the most advancedtochriquo available. Those Gsheets were subjected to different wetpressures, dried, conditioned in a humidity room, and the solid frac-tion and tcnsiie strength accurately determined. The solid fractionrange studied was 0.15 to 0.5. The following conclusions arc drawn

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from the data presented. Tensile strength increases in a regular mannerwith increase in solid fraction in the test sheet, the relation approach-ing a power function. The curves of tensile strength plotted againstsolid fraction change in an orderly and rational Tanner when a pulpis beaten or when it is dried, the two treatments producing changes inopposite directions. Tearing and bursting strength and folding endurance

..-. - - in-an-unbeaten. pulp vary- with -solidfraction in thesame-way that they - 'vary with.time or freeness on beating. The beating process may bedivided into two parts, one in which strength increases are due to an _

- .-actusl change in the surface conditions of the fibers, and the otherin which such increases are due partly to solic fraction increasesdependent upon increased shrinkage and, therefore, upon decreased fiberparticle size. The second of those effects can be duplicated by wetpressure but the first cannot. A means is thus provided for studyingr-c;arately the effects of fineness in boating and of some other factorapproximating true hydration. The regular nature of the changes observedsupports the hypothesis that this sheet'strength is a function of sheetstructure and fiber properties, which can be expressed mathematically.

747. Doughty, R. H. Tnc relation of sheet properties and fiberproperties in .ppor. II.' The variation of ultimate tensile strengthwith basis weight and related factors. Tech. Assoc. Papers 15:361-367(Juno, 1932); Paper Trade J. 93, no. 15:44-49, 54(0ct. 8, 1931); T. S.93:275; B. I. P. C. 2:135; C. A. 25:5987; B. C. A. 1932B:718.

In socking an explanation of the fact that the breaking length ofpaper (ordinarily used as a measure of ultimate tensile strength) is notproportional to basis weight but, on the contrary, reaches a maximum asbasis weight is increased from a low value, a series of test shoots ofseveral basis weights, wet pressed at several pressures in order toproduce various fractions for each basis weight, have been preparedand analyzed. The variation of ultimate tensile strength with solidfraction at constant basis weight and with basis weight with constantsolid fraction and the variation of solid fraction with basis weightat constant wet pressure wore studied. The results indicate that thecommonly observed relation between, breaking length and basis weight isgoverned by uncontrolled combinations of the three variables considered.Variation with basis weight is due primarily not to variation of basisweight as such but rather to fiber orientation as a manifestation ofthe variation in consistence when sheets of different basis weights aremade, using equal volumes of stock. The following conclusions may beapplied to paper sheets in general. Shoots of constant basis weightshow a mathematically regular increase in tensile strength with increasein solid fraction; the increase in solid fraction is obtained by in-

crease in wet pressure. Sheets of the same solid-fraction values showa regular decrease in tensile strength with increase in basis weight whenthe volume of stock used in their formation is kept constant and, con-scquently, the consistency is varied in proportion to the basis weight;this strcrgth decrease is primarily a result of the consistence changerather than of the weight change. Sheets made up under constant wet

pressure show a'continuous increase in solid fraction with increasein basis weight, as a consequence of greater shrinkage on drying. As oresult of the-two effects just noted, sheets made up under constantwet pressure and with a constant volume (variable consistence) of stock

I IMWAMMO

tTensile Strength ;26

first increase and then decrease in tensile strength whon base wight -

is increased from a low value. The relations involved may bo oproCoi

as S = tCll-', whore k is a characteristic of the pulp that is doeiBatod

"fiber strength at unit consistence," and m and n ngy mrr naot bo ecrt0- s

istic. Shebts of low basis weight (e.g., 21.5 pounds)-show an onarnlol fl'

---behavior that nay bo citheor specific or an effect of inaccuracy in

thickness moesuremcnts. The various effects of basis weight appoor to

be explainable from the.standpoint-of the fiber arrangement, porti-

cularly the concept of orientation of fibers perpendicular to the

surface of the shoot.

748. Doughty, R. H. The relation of shoot properties and fibor.

properties in paper. III. The effect of fiber length on shoot propertioB:

preliminary oxperioents. Tech. Assoc. Papers 15:137-142(Jtme, 1932);

Paper Trade J. 94, no. 9:29-34(/arch 3, 1932); C. A. 26:3108; T. S. 95:

75; B. C. A. 1932B:718.

Two unbeaten pulps--a spruce and a black gun sulfito--wore separated

by vet screening into long-fiberod and short-fiberod portions; tho

fractions paosing a 60-mosh screen and that retained on the 32-mosh scroon

were used. Thcsc two fractions, as well as the whole pulp, were mnde

into sheets which wore subjected to various pressures while they wore

wet and the tensile strength and solid fraction values of tho dry sheets

were determined. Toc moan fiber lengths of the short fiberod portions of

the spruco-anti gum pulps were 0.2 and 0.07 rmn.; of the long-fiborod

fraction, 2 and J.5 nm. The mean lengths of the wholc pulps wore 1.3

and 1.1 amn. hects mado under any given pressure while wet from tho

ehort-fibored portion are front 25 to 200% stronger than those iron

the long-fibeord faction. The short-flbered fraction givos a shoot

of higher solid fraction and, therefore, of greater strength than one

of the long-fibered pulp. HowevCr, fiber length does not have a vary

grcat influence upon the strength of sheets at any given solid fraction.

Theor is a fundamental difforenco in the interrnl structure of sheeto

nado of fibers of different lengths, manifested in this work by the

porosity test, that nay be more evident by strength tests other than

tensile strength. There are also differences in heeot-producing

properties between pulps that cannot be oxplainedl by fie'cr length

differences alone; possibly these are ascribable to the chemical nature

of' the material.

74,. Fournicr, Raynond. Determination of' the tensile strength

of paper. Pap)tcric 53, no. 17:1066, 1069-1070, 1074, 1077(Sept. 10,

1931); Pulp Paper ang. Canada 31, no. 44:1193-1194(0ct. 29, 1931);

C. A. 25:5987; T. S. 93:276; B. I. P. C. 2:136.

When cutting out a test strip for the dotermination of tonsilc

strength, the edges of the strip nrc mutilated and therefore weakened.

The results of the test, therefore, are too low and represent the actual

strength of the original papor - les the decrease resulting from the

rntilation along acah edge of the strip. 4s the latter is inelopondnt

of the width of the strip, the results obtained with wide strips arc

proportionally higher .than with :nrrow strips, up to a certain width,

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abo-e wnich the results are practically proportional to the width.

... --. s the construction of instruments with wide Jaws offers certaindifficulties, Fournier proposes that the instruments at present In use be retained but that the strips be at least twice and prefrablythree or four timed as wvie as the Javw (15 in.). The toet would besimplified (less care required in preparing the stripo), the results

would be higher and would more truly evaluhtfethe quality of the paper-- - . .undole th conditions of use.

- 75. -Fournier, Raymond. Dotermining the tensile strength ofpaper. Papicr 25, no. 10:457-440(0ct.,'1922); Paper Trade J. 75,no. 23:50-51; no. 25:58(Doc. 7, 21, 1922); C. A. 17:208; T. S.75:306.

Fournior, after briefly discussing the shortcomings of theinstrument generally used for measuring the tensile strength of

paper (Schoppor), advises using a machine which could take a imchwider otrip--c.g., 15 cm. instead of 15 mm. This would necessitate

the use of forces up to about 300 kg. and Schoppor typo instruments

of this capacity would be too heavy, cumbersome, and expensive. A

simple and efficient hydraulic type of instrument is doscribed,in which the tension is exerted by means of a piston displaced by

screwing a rod into the cylinder carrying the piston.

751. Goodbrand & Co. Ltd. Goodbrand tensile testing machine for

paper. Circular with no number or date.

Trnrce types are illustrated. SoC also World's Paper Trade Rev. 112,

no. 22:143', 1488(Doc. 1, 1939).

752. Griffin, Roger C., and McKinlcy, Rusosll W. Studios of

tensile and bursting tosts. Paper Trade J. 102, no. 2:34-55(J-n. 9,

193;); Tcch. Akssc. Papers 19:222-225(Juno, 1936); B. I. P.. . :275;

C. C . 1953oB:lo; C. A. 30:2378; T. S. 103:191.

TAPI Standnrd T Il4-m specifies that the stressing Jaw shall bc

onrat,,l-ct a ns aod of 12 inches per minute and that the testing in-

strimnnt shall be of such capacity that the tensile strength of the paper

tctoed &;ill not beo svrotr than 90 nor loss than O1d of its capacity.

Clar!k has proposed that the break shall occur within 10 to 0' seconds

from the tine tho load is applied. Using a Schopper tensile machine

(powor driven), a series of tests wra made in the machine and cross

directions of seven samples. When the TAPPI method was employed, only

four of 11 groups of strips tested gave results outside the time

limits of 10-30 seconds proposed by Clark. Of the 11 groups of

duplicate tests, the overage deviation was 2.8%; in only 2 casco

was it -over 5%,. eIcn all 11 groups were run within tho proposed time

(10-'0 seconda, the avcraec deviation was 2.6%. The tests indicate

that rapid application of the load tends to give somewhat higher

toenilc strengths. The quantitative effect, however, apparently varies

with the type of acpor. From present data, there do not scene to bo

sufficient advantageo in the proposed modification to warrant incor-

porating into the standard procedure, except as a sugcgstion. It is

Esugcosted that the method require the recording for each break the Lime

in seconds frao the application of the load until the break occurs,.

-I IC�C�ar�c�mnr�ar�r�-�···me


73. Grund, E., and Weidcnrmnllor, H. The zero-breaking lengthof pulps and papers. Popior-Fabr. 30, no. 24:397-04( Juun 12, 1932);C. A. 26:4714; T. S. 96:136.

The breaking length of sheets rade from certain pulps. and- of ...various cormorcial papers wao determined by the use of the 'bintherzero clamp" on strips of zero length. The zero-breaking length valuesof pulps change only slightly between 30 to 0O degrees Schoppor, .but from 90 and above it begins to decrease. Tne zero-breaking longthof pulps is independent of the basis weight of the test shoot. Byshortening the length of the strips of paper tested, the breakinglength incrcascs. By means of these tests, the actual fcltingproperties of the fibers can be separately determined.

7j4. Harrison, H. A. [Tensile strength]. Prcc. Tech. Section,Paper Makcrs' Assoc. Gt. Britain Ireland 11, pert 1:77-79(0ct., 1930).

In a discussion of Olivcr's paper, Harrison gave figures'on thetensile strength for strips 1 inch and 15 m. wide and calculated thestrength of. a strip 15 mm. wide from the values for the inch strip.The data confirm the results of Houston that decreasing the widthof the strip increases the relative strength, yet this applies onlyto tests carried out on papers cut in the machine direction. Withcross direction strips a decrease in the width of the strip causespractically no difference (in one sample of unglazed kraft a do-croase of 11.3% was observed when the narrow strip was used). Thereis no general agreement on the effect of the length.of the test strip.The rate of movement of the lower jaw of the Schoppor tester is men-tioned but no data are given.

755. Harrison, V. G. 11. Papcr testing. IX. Tensile strength.Patra J. 2, no. 3:l19-122(Nov., 1938); B. I. P. C. 9:254.

The Patra laboratories usc t.hc Schopper tensile strength tester.The samples arc 5/8 inch in width and not less than 8 inches long.Tosts arc made in both machine and cross rlirections. The method ofmaking the tcot is reported in detail. The procedure follows thereconnmrndationo of thre Paper Testing Corrmittcc of the TochnicalSection, Paper liakcrs' Association. It is rocormonded that thedriviDg handle of the apparatus should be turned at the rate of 150r.p.m. when the smaller wi'ght is in use and at 50 r.p.m. with thelarger weight. The average of ton readings is taken. Thin or weakpapers may have several strips broken together.

_76. TIoritage, C. C., and Doughty, R. l. The relation of shootproperties 3to fiber pronorties through a shot structure. Tech. Assoc.Papers 13:21-25(Moay, 1.930).

This is a briof discussion o"' tho work of Doughty (Nos. 746-743).

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. Hcrzbcrg, W. Influence of folding and printing on thestrength of papor. Mitt. kgl. nech.-tech. Versuchs. 1899:269-284;J. Soc. ChCan. Ind. 19:267.

The apparatus used consisted of a heavy (7.5 kg.) iron roller - -

(150 rnn. dianctcr) provided with a central flange fitting exactlyinto a groovcd rail, along which the roller runs. A strip of paper, 15 r. wide, likewise exactly-fitting the-groove, is folded backupon itself, laid in the groove, and the roller run over it, inboth directions. After rceloval the paper is tested for tensilestrength. The difference between these numbers and those obtainedwith the original unfolded sample expressed in percentage of thelatter gives the "loss in breaking strength" and "loss in stretchingpowcr" of the paper on folding. Some 87 papers wore examined. Theloss in stretching power was greater, both in machine and cross direction,than the loss in breaking strength. The loss in breaking strength in thencchinc direction is greater than in the cross direction. The loss instretching power in nst cases obeys the sane law. The lowest ncanloss in brcn!-ing strcrgth observed was 4.7% and the greatest was 48.5%.The lowest loss in stretching power was 14.3% and the greatest was 78.7%.

758. Icrzberg, W. Influence of weight per square notor on thestrength of paper. Mitt. gl1. Material. 31:318-320; Papicr-Ztg. 39,no. l:3(Jan. 1, 1914).

759. Hcrzbcrg, W. Strength, stretching and folding numbers ofpapers in both directions. Mitt. kgl. Material. 27:172; C. A. 3:2870.

Drcaking strength, stretch and folding numbers of paper vary ac-cording to the direction in which the test is nade on the paper. Acomparison of tests rado in machine direction with those in the crossnrchinc direction gives ratios front 100:18 to 100:31 between the twodi'roctions in breaking length, front 100:290 to 100:455 in stretchand fr'on 100:21 to 100:1.5 in double folding tests on certain Manilapcpors. IIfrzborg advocates classifying papers, not on the averageof tests ilndc in both directions, but on tle lower value found incither direction.

760. Iouston, Paul L. Effect of length and width of test specinonon the breaking strength and elongation of paper. Paper Trade J. 76,no. 12:54-55(i;1rch 22, 1923); Tech. Assoc. Papers 6:72-73(June, 1923);T. S. 77:1.

This study was .adoc of a breaking strength machine of' the inclinablety-re wi th a cuapcity of 50 kg. Ten different lots of paper wore tested;sc:-nles wcre cut 0.25, 0.5, 0.75 ond 1 inch ir width and of such lengththct tlho distarnc between thc jaws of the machine was 50, 90, 100, 150,anl 180 rm. The machine was so set that the lower jaw descended, at aspeed of 6 inches nor ninutc. Thc test results vary when differentlengths of the salue width specimen are used; however, this variation

I.0 -.S;

Tensilie Strenglth 271.

was never greater than 1.5 kg.-, which is domparablo with the experi-mental error of-the machine. The percentage elengotion varied withboth the width anid the length of the specimens. The elongation, ishighest for the 0.25-inch strip and lowest for the 1-inch strip--i.e., in the inverse order of the width; the some, isejtruo-of tc-------

__ lngt.- -Whz--c- xn~ineb~t~h~ecttha thre is a differencein stressed area as well as fiber adjustment to stresses. 'The rateof stress per unit arca _decreases nos-the--stresrjed arcw- docro"666s

- -- - 1t ism-ohalulie&d that t~he !length of test spocinen t is nt important-hn- only the breaking l1enth is desired. However, fteprbty

elongation is desired, the-length and w~dth Tait bo controlled andstandardized. It is suggested that aI l-enth of 3.5. inches (about 90 mm.)and & width of 1 inch (about -25 mm.) be adopted ns a standard.

761. Houston, Paul L.. Rfleltionship between breaking strengthand bursting strnenth, of paper. A possible calibration of the Mullentester. Paper Trade J. 70, no. 13:47-48Q11arch 29, 1923); Paper 1.-kors'14o. j. 61i, n6. 5:128-189(May 15~, 1923); Tech. Azsoc. Papers 6:100-1o1(Juno, 1923); T.~S- 77:1.

The apparatus employed was a 50-kg. breaking strength machine anda Yzzlien toster with anil attachment for measuring deflection. Jaws forthe breaking strength machine were made to) use test specimens oneinch in width. T1he attachment for the Matllon touter consisted of adrum, which wan gearedt to the hand wheel. A recording pen was attachedto a very small rbd in such a way that it could move up, and down anddescribe a curve on a chart clamp-ed to the drum. A thiclamcss gagewas also fastecnud to the Mullen tes2ter. flet~riminations we~re made ofthe brerkLng stirength, elongzation, and bi'xsting, strength. As thebursting strength wans dotermmnedi, the increasing Jciloctirn of' the paperwas recorded on thel chart, fvmion which the blengantion At the~ breakcingpoint was calculatoti. PesuLte arc ren~orbd for eight kin-ds ra aper.They- shlow that the oietg vorntioton, of' ratio of break-ing- strengthto elo~iigtien and, of' rcmtib of bursting streOnLgth t- o, eongation f'_romthe mean value is vc~i'y smn1 f or each gradeo of' paper (this can be, ox-tlaifrod by experimo.nta' error~s in the initial Lest~ reandings. Tihu, itappears that there is a direct. relationship betLween breaking ami-dburstinG streng-ths. If' the rlto (break-ing; strength)/olongo1tion

(bursingotrong~th)/elongatlon c-ar be checked, it th,.-1t be used. as apossible moams of' calibrating; the IMulln tester and creat'ing1 a standardbursting streng-th machine.

762~. Influence of the thickness unpon thntreng~th of paper.Wochbl. Papio:rfhbr. 49, no; 52:26&1-2682(Doc. 28,, 1918); 50, no. 3:136-137(Jan. 18, 1919).

The tenscile s-trengths of papers, 24, IL5 and 92 -. /sq. cm).,were 2350, 3470 6n'l 3810 meters, respectively. In the second article

values for panors of sp. Fr. 1.225, 1.300, 3.tO3, 1.160, 1.120 rniV- 1.1d3 xrerc;4604, 4734, 3233, 2809, 2881 anid 2464.

4

____ - -------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1 1r"

Tensile Strength27

-~~~~ Institute ofl Peper Chemistry..- Measurement of the tensile --

o trengbh rif rarer. I. General considerations of the factors affectingthis measurement. raper Trade J. 115, no. 5:12-18; no. 7:13-22; no.19:16-221(July 30, Aug.- 13,.Nov. 5, 1942); Paper-Maker 104, no. 4:TS253- 60o(ot., 1942); B. I. P. C. 13:154; C. A. 37:530k

in, the sneciseon. TFolletving this clasoif'ication, pendulun, inclined-olone, hydraulic, and spring types -of instruments are described - The-

. I o clirating the severaltyoofI -u sis- t p e i n tr u m n t

discussed. It is bhetni that pcoidulum~-typo testers should not becalibratedd by al-lowing the test weight- to ride down on, thle lower clbmp

because the follow-through of the loaded pendulum causes a seriouserror, porticulanily at small loads and high clamp speeds. Calculationof' the 'follow-through of the pendulum of a typical inztruncnt intheactual testin.- of a spocirien shows the follow-through t~o uob rnchsmaller than that of the pendulum. leaded with the dead weight and tobe neglig-ible except when. weak papers are tested at hig~h speeds. Theeffects of rate of loading,, opecimon length, and specinon. widthare reviewed nnd additional dataonre presented. Tensile strength in-creases as the rote of loading increases and docreasos as the specimenlength inc~resces. It appears that the relative tensile strength(teonsile streng~th- per unit width of specimen) should be Independentof pecimen width for wide specimens but that it should decrease

rapidly for widlths less thanr approximately half can inch. Data aregiven for rates of leading of 3, 6, g, 12, 15, orA 18 inches perminute, for specimens 2, 4, 6, 7 . 0 9 r and 8 inches In length, and forspeeds of the stressing clamp Of 3, 6, 9, 12, 15, and IS inches per

minute.

+~ ~ 76; In~itibulta, of Penner Chemistry. Meisu~rocmnt of the tensilestrerrth of pe-per. II. The &cott Serig'raph, Model 35. Paper Trade Cfl115,Y nO. 2b:14-21('Doc. 21, 1942); B. I. P. . 13:20%.

The~ lnstnz'~ient is of the pe-ndal-um type- and has two range~,s, 0 to 55poundsI, end 0 t1o 110 nound's, -with scales g~raduatod in hfalf' around and.

pO~ndS, reseetirly'. The lower range -' is effective. when onl- theo fixedweight is use-,d on the tendulum and t1)e 2irgher range is effectilve,when an ouxi1liarY we-Cigh is added to the peniduluA. The tensile scales-are rearkt d en a circular dial whorec indicator Is coupled, to the

pondluithrough (•ears. The lower clamp is fastoned to a thrcreaddred. which ic motor driven throug-h a gear box and a variable, steeod nulley.Thec speed of' this lower clamp may be varied continuously 3ru to 20inches' norl :inuto. The upper clamp is connected to tile penduluma by achain pnssiina around and anchored to a pulley w-hich in turn is~ fastenedL

be the pendulun aend is coaxial with the bearing of thes pbndulun-. The0jaws- arecqesippcd with interchangeable anvils of' 1- ande 3-inlci wid~ths.~he Liistrurer~t is equipped with ai recording mechanism for tree in-

loa-elngaioncurves. The chart carriage is drarnn dow,,,nwrds3 byageartrai copledt to thre lower clamp, thus assUrIng that the chart

roves at speed propiortional to) the sneed of' the lower jaw. TZhe percarriage" naoves hoi-rizontally and is connected! to the penrlulun by a red.

f1TIIlIIii�iiiIfiulinL.j IU.s..u. �' L. -IM

~I------- ~ * - _

Tensile strength 273

The particular instrument studied is in error at a number of pointsalong its scale. For many applications to control testing this erroris not serious. For many other applications it is serious. Inaddition, friction causes errors of as much as 1.5 pounds. Neithersource of error is due to faults in fundamental design and-both-couldbe eliminated by-the manufacturer.

-- 75. Institute-of Paper Chemistry. Measuremont of the tensilestrength of paper. III. The Amthor universal tensile strength tester.Paper Trade J. 116, no. 6:10-12(Fob. 11, 1943); B. I. P. C. 13:279;C. A. 37:2176.

The instrument is of the pendulum type and has throo ranges: 0 to200 pounds, 0 to 50 pounds, and 0 to 15 pounds witlh scales graduatedin pounds, quarter pounds, and tenth pounds, rcopoctively. The rangesarc charged by changing the weights on the pendulun. The three scalesare marked on a quadrant concentric with the axis of the pendulum,and the load is indicated by a pointer fastored to the pendulum whichmoves over the scale. The upper specimen clamp is connected by meansof a chain to a sprocket on the shaft which supports the pendulum.The lower specimen clamp is connected to a threaded rod, called aspindle, which io motor driven through a belt, clu':ch, and gear box.In this particular instrument, the lowor clamp is drlivcn at a constantspeed of 12 inches per minute. The Jaws of the clamp are one inchwide. The conpictc instrument, including the motor, is mounted upon acommon base. The pcndulurm swings in a plane oprpcndicular to tho frontof tho instruriment. Wnhn a pecimnon brooks,, the pcndulvm is hold atits position of mUcxtirun displacement by par.ls vhich engage tooth onthe quadrant which also boars the scales. Theo ilcr jaw is broughtbockc to its starting position by morin, the opocating .over to itsupper position. This starting position' nay be sct at any desirodpoint by aljucstmrnt of thu stop on the rod which control -th^ clutch.For srccinmcr len:ths less than six inches tho up-;cr cinnmp :L:at beloavrcd by shifting its chain on the sprocket. Tlio spindle projectsbelow bolow the level and in front -f the base during pari; of itsmotion, so that the irstrulont must be cst with itn base fluoh lriththe edge of the table. Two scrcws are provided at the back cf theinastriunt base to pornit levelling tho inctruziont in the paine inwhich tho pcnduluml sa-ins. Thec instrument is equipped with a devicefor indicating tho elongation of the specimen. The dial of thisdevice bears two scales, one giving the olorgation in inchos, theother giving the stretch in percentage for a six-inch specimcn. Thecalibration of one prcuimnably typical instrurinrt wao studied; thcgreatest error found by doad-wcigit loading was 0.54i, but noasurcnents of the saall divisions indicate errors up to about 0.7% of full-scaleload. This error is not serious in most applications of the inntrurecnt.It appears that the errors in the calibration are due to inaccuratedivisions of the scale and arc natters that can be taken care of bythe manufacturer.

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766. Institute of Paper Chemistry. -Measurement of-the-tensile--- - -strcdgth of paper. TV. The Schopper electrically driven strengthtester. Paper Trade J. 116, no. 9:13-l4(March 4, 1943); B. I. P. C.13:324; C. A. 37:2933.

The instrument is of the pendulum type and has two ranges: 0 to_-……„j --_ _ _ _ -15- pounds_an-0 .to -75--pounds-with-scales- divided-to-1/32- pouhd-andi I/4--...

pound, respectively. The upper specimen clamp is fastened to a chainwhich passes around and is anchored to a quadrant coaxial with the ---- ' - -

._ _ .- .-- --- boaring-ofrthcpon'dulum.; Th e 'oier- specimen clamp is fastened to a rod whichis draem downward.-by means of the mbtor-driven gear box.The speed of the lower clamp is continuously variable from 2 to-20inches per minute. These clamp cpcds afford rates of loading varyingapproxinatcly from 0.6 to 6 pounds per second on the 75-pound. scaleard approximately from 0.12 to 1.2 pounds per second on the 15-poundscalc. The separation of the clamps is adjustable to distances of2, 4, 6, aned 3 inches. In this particular instrument an extra holewas drilled in the rod which holds the lower clamp to permit aspecimen test longth'of 7.09 inches (180 mm.). The scales arb markedon a quadrant vhich also bears teeth which engage the powlo fastenedto the pendulum to hold the pendulum in its position of maxitaun dis-placement after the specimen breaks. The lower clamp is returned toits starting position by moving the operating lover to its upper posi-tion. The complete instrument, including the motor, is mounted upona base. Errors were found in the calibration'of one instrument,presumably typical. These errors are not serious in many controlproblems, but they night be serious in other cases. The error appearsto be due to inaccuracy in division of the scale and not to afundamental fault in design of the instrument; therefore, it couldbe corrected by the manufacturer.

767. Isnard, Raymond. Analysis of cardboard. Elasticity.Paper Trade J. 73, no. 16:40, 42, 44(oct. 20, 1921); Papotcric 43,no. 13:578-586(JuJ.y 10, 1921); C. A. 15:3205.

In tho apparatus described, a strip of cardboard 1 by 10 cm.is supported on knife cdges exactly 50 rm. apart, so that 25 rm.project at either end. A graduated lever, pivoted at one and,carricu a third knifo cdec by moans of which the load is applied to.the middle of the test strip. The weight of the lever and knifecdgc is' balanced by ooans of an adjustable counterpoise and theload is varied by rnans of a rider on the lover arm. The methodof calculatinr• the elasticity is given.

|. . TEsrarn, Rauynold. The analysis of cardboard. Tcnsilestrength ad cori-poition. Pnpctcric 44, no. 2:50, 55-54, 57(Jan. 25,122~); Pap-r T',ad J. 74, no. 24:51; C. A. 16:1151.

Isnardd describes a home-rade apparatus for testing the tensilostrength of cardboard, which may be mado to indicate the elongationif desired. it is not as accurate as the instruments at pr-scnt onthe market, but it is sufficiently accurate for the purpose ard ischeap and simple.

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769. Jahans, G. A. Auxiliary paper testing instruments. Zellstoffu. Papier 14, no. 9:359-360(Sept., 1934); B. I. P. C. 5:45.

Suggestions are given for the construction of'a simple bursting-_ ------ e-and a-tensi-le strength testing-instrument-f f--uffic'ibnt accuracy for

practical operation when only comparative results are required.

7'7. Kicnzl, Hubert. Breaking strength and extension. Papier-Fabr. 32, no. 48:482-485(bec. 2, 1934); B. C. A. 1935B:222; C. A. 29:6054;T. S. 101:238.

The product of breaking length and stretch of paper as a measureof its capacity to absorb work is discussed.

771. Kirchner, E. Breaking length and breaking strain. Wochbl.Papicrfabr. 48, no. 36:1581; no. 41:1792(Sept. 8, Oct. 13, i 9 17).

- Strips 15 m. and 9 mm. were tested with 3 kinds- of papers; theresults with the 9-ms. strips were 2.3, 3.7, and 35.5% loss than thecalculated values.

772. Korr, R. Uniform testing of' papor with reference to strength.Papior-Fabr. 27, no. 36:558'-562(Sept. 8, 1929); Wochbl. Papiorfabr. 60,no. 36:1107-1ill(Sopt. 7,. 1929); Zellstoff u. Papior 9, no. 9:612-514(Sept., 1929); C. A. 24:3366.

!-" Seven samples of commercial papers were tested for uniformity in

tensile strength, fifty tests being made in each direction on adjoin-ing portions of the sheet. Under those conditions the maximum differencein 50 tests varied between 9.4 and 33.4%h, the average deviation fromthe mean. being + 1.8 and + 6.1!, and the probable error of the meanbetween + 0.23 anl + 0.7'4. Scamplos taken from different sheets mightbe expectcd to show ,reator divergence than this. There appears to bono definitely greater uniformity in one direction than in the other inthe samples tested.

773. Korn, R., and Boerner, Cl. Experinents rith 'the Schoppertorsion- tester for determining the number of twists in cable paper.Wochbl. Papierfabr. 65, no. 51:897-899(Dec. 22, 1934); Papior-Fabr.33, no. 1:2-5(Jan. 6, 19355); Zcllstoff u. Papior 15, no. 2:52-54(Feb., 1935); Papier-Ztg. 59, no. 95:1642-1644(iNov. 28, 1934); B. I. P. C.

5:1350; B. C. A. 19355:143; C. A. 29:6054; T. S. 101:238; 102:10; 103:27.

The number of twists under a definite load up to the point of rupturedecreases as the paper thicknoss increases. However, no mare:d differences

were shorn by papers ranging 'rom 32 to 92 grams per square motor.Differentiation of such.papers is more easily carried out by determiningthe load of rupture in the maclino direction..

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774. Landt, G. E., aid Rulon, S. A. New interpretations ofstructural aspects of the paper sheet. Paper Trade J. 111, no. 4:32-36 (July 25, 1940); Tech. Assoc. Papers 23:282-286(Junoe, 1940); B. I. P. C.]0:461; C. A. 34:8277; B. C. P. A. 1940B:783.

This paner is an exploration of- certein- fundamentals- of -p-pi struc-.. turc. It is postulated that ell the physical characteristics of a sheet

of paper must be related to (a) the primary valence linkages. in thecellulose chain molecule, (b) the forces of molecular cohesion: betweenchains, and (c) conjugated surfaces. When a sheet of paper is rupturedin any physical test, the feltod fibers must be twisted or compressedto destroy the conjugated surfaces. When a tensile stress is appliedto a shoot, the fibers will first slip whore the conjugations are dis-rupted; it will then shear along the lines of cohesion parallel to thefiber,, and finally break at the atomic linkages across the fiber.Using cotton pulps, it is shoin that the tensile strength is higher forthe pulp having a reater viscosity; the tear shows the opposite ten-dency. Tvo pulps, with viscosities of 626 and 129 seconds and frccnoocsof 695 and 715 cc. had tensile strengths of 8.5 and 4.0 and tears of 114and 14i. A rag sheet from a pulp of high viscosity and beaten for 30,90, and 180 minutes (freoncoses of 695, 205, and 130 cc., respectively)hod tensile strengths of 8.50, 21.56 and 29.12; the tears were 1.4, 128,and 137; this represents an increase of 244% on boating. A similarchange is produced by the action of zinc chloride on a shoot of waterloafpaper. Thus a sheet with a tensile strength of 15, on treatment with68 or 71% zinc chloride for 1 minute at 60° or 120 C., had a tensilestrength of 21.1 or 44.1; the tears were 67, 80, and 129, respectively.Other experiments show that the tensile strength is increased in thedirection of the tension, values for the machine direction being muchhigher than in the cross direction. There is a theoretical discussionof the results, especially of the hydration theory.

775. Leunig paper tester. World's Paper Trade Rev. 79, no. 9:788,790(Iarch 2, 1925).

A description is given on an improved model of the Leunig paper tester.The tester is fitted with a graphic recorder which enables the operator todetcrminc tho proportion betreoen load and elongation at any moment ofthe toet. The1 recorder can be applied to the motor- or hand-driveninstruiont. The standard strip is 15 mm. wide and 180 nn. long. TheEnglish strip, 5/8 inch wide and 12 inches long, is the nearest equivalent.

776. Lofton, R. E., and Synder, L. W. Results with testers for measuring tonsilo strength of papor. Paper lradc J. 86, no. 24:65-66(Juno 14, 1928); T. S. 88:199; C. A. 22:3296.

Six typos of testers wero studied; these are described briefly, butthe nanmo of the manufacturers are not given. In addition to suchmechanical details as runged-ncs of construction and ease of calibration,a good tensile tester should fulfil two roquircrcnto: The results obtainedby testing duplicate spccinons of the same sample should check reasonablywell and the average (chcclcod) results should bo reasonably near the truth.

I----* 1

T_,si.. S-c,-h 277

The results can. harfdly be cxcte-c tchckrcCI other within. about 5c/; this-- - figure may be tak-en. as a measure, of' the heterogeneity of the paper. Hone

of' the Instruments shoved any appreciable change of' accuracy in different,parts ci' the scale, vti the lImits exaniinod. An instrument may giveresults vchich chock each other closely,and. yet all the results maWy be farfrom the truth.

--- 777. ~~~-Messmr,7r1 11; B.'c -Pper tct~ing ntdh~hbd Pzc. Tech.,Section,Paope: Makers' Assoc. GCt. Bikitein Irelaond. 8, part l:77-87(Oct., 1927T);World's Paper TraOde fld1v._87, no. 15:1164, 1166,W.68;. no. 16:1252, 1254,1256;'disciission, no. -17:1362, 1364-1365(Aoril 15, 2?, 29, 1927); Paper-.-Makecr 75, no. 5:486-487, 489(ilay, 19c27); Paper i-takers' Me. J. 65, no. 5:125-l186(may, 1927); T. S. 85:240.

The Sehopper tester was introduced -into Er-,lard cc- the Inunig tester.The principle of using, dead. weight to apply the breaking load, as usedToday, is exactly the some as in the first machine. Certain improvementsxre detailed,. _Rcpcrine'-nts have shown that6 the results of tensile strcergthtests depend on the speed at which the load ia applied to the test cample.A menan of determ,:i7dninc the correct speed. and checking its constancy js

nrujvidced in. Alt's diaphroag aj~paratuis; it coy). be used as a recorder toregister the actual tcstling speed or as on apparatus for predetermiflinC;thes speed at which the test should be carried out. The ~'aphic recorder,fitted to a paper tester, records alo0ng the horizontal axis the breakingstrcenth and along7 thes vertical axis the elongation. The breaking lengthis that length of a strip of)i paper of any uniform width and thickmcss

which, if ruspended. freely at, one end, will break,. by reason of its owrnweight, at the point of suspension. This r.Iethod. of expression indicatestile specific tencilc strengthi of the sheet, irrespective of the wtdthof the tentu strinl. The11 breaknigt lcrgth can be calculated fron the breaking

strength and the subpotaces of the sheet; it is genracrlly expressed in rioters.-* If' G Wis h weig~htu in ;~'an of a strip -180 =ai. long and the breaking, streng,'th

in- P hg , th thle brancing leng-th is 0.1SF/c- !Im. The Lenigr tester is¶r-nuuatentI, in the Brlitis, system of 'Jigtland mno-asres.

77.Mcetxct, i.Graphical calculation of tearinjg lengIth and 1oat.Pm~ier 34, no. L:363-361%, ~167-36G, 371l(April, 1931).

A chart iscivcn fromn vahich can be calculated the tearin g lengtLhwhen the weight part square moter and the tearing load- arc known..

77. Motor driven tensile strength tester (Pnthor). Paper Trad~e J.86, no. 11:58(March 15, 1923).

* This teste r is bult' or, the :inclination ba)lance principle with thependulum hovinC at maximun ang-ular swingr of 45 -degrees. The load isbalanced by the inclin atLion of the lover aind is reflected directly to

-the quadraont scale. The pulling clamap is attached to the upper end ofa guide. tube which gets its uniform linear speed of 12 i'nches per mnitrtethrough a chain and sprocket driven by the motor through the speed rc-duction unit. This u-nit consists of' a double sot of worm gears runningin heavy annualar ball. bearing lit wi oil. 1)th. A feature of the motor-driven unit is the sealmed menrcury-to-mercury contact switch through whichthe current is fed-O. The operation of' the tester is~ described.

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ITensile Streng~th 273

~.. 780. National Association of Purchasing Agents, Inc. Corrugatedfib-reboaril. shipping3 containers. No. 19, 1934. £U P.

Tensileo Str-itli7(, Test. This test is only applicable to individual~listsat inebord nd orrgatngmedium-- it cannot be applied, to Combined

board or finished bores. Tout specimens shall be cut from unrw'inkled, -

--uncressod. anid. vmblemil.shod shocot, four each with the grain runninDg the lonc,way and the chart way of' the specimens. The specimens mist be cleanly anid

- accurately cut, with parallel opposite edaes,- not less thtan 12.7 mnn(0.5 inch) nor LlorLethman 25.4 mm (1.0 inch) wide, and of such length thatwhen clantued in the toter the distance between the jawss shall be not lessMien 5 tiesnr more than 12 times the width of the samnle, but in nocauie shall- they be loss then 140 mm. (5.5 inches) lonr. The exact sizeshnll. be determiynd according to the tester and itrs convenience iLn opera-tion. The specinen shall bo firinay and squarely clamped in thJe jawS ofthe clamps and thoe stre~ssing~ clomp then operated at a constant speed of30.5 cm. (12 -Incites) per minute until the specimen breaks under the tension.Testls in which the specimen breaks at or in one of the clamps shall be dis-regarded. The tester should be atf such capacity that all tests 1.ill fallwithin thd range franl 10 to 90% of its capacity, Tha breaking loand shallbe recordedl. Lo the nearest 2%~ of the total indicated reading and shall becalculated in kilog~rams per 15 =r. width of the specimen. Not more then.one of the four testsin. each direction at' the stack nay fall below thespecification, with the average aof the four tests meeting the reqlulrdnent,for compliance. However, if 'the initial tests in either or bath directionsshall fail to cenply, a series of 12 re-tests of either or bothi (accord-ing to the failure) shall be naadb,. of which not more than three testsYnsy fall below, with thea averarge of all 12 tests complying With the speci-i_'iation, for aceon3tanco.

Y(8L-. National Th'~reau of Standards. Stuructutral fiber insulting, board.3-4 cd. Cormrercial' standard 0S42-43. 2 943.-

The test -far torsile strength slhall bo as follows: Forl'n echl snrinp"Spy cincens 2 inches wide- and not les,-s than 10 inches long shall be clean cutpnrallel to the Jlong~~St direction of the board~ and at right an-les thereto.Thc: distance between. dents shall be not less than 6 :ineheC. Besults onsnecimens under. test thant break, within. 0.5 zinch at' the jawls shall. be dis-regardedt. The =achine speed shall be set for the openings between thedlames at the rote of 2 inches per minute. The specimens before beingoninced in the testing3 machine shall be assured for width and thieconcssto thec nearest 0.01 inch. The tensilo strength shall be taken as Lheaverage of three specinens from eoac direction of the board.

782. National Bur-nu of Standards. The testincg, of paper.. CircularNe. '107. Fejb. 12, 1921.

A brief discussion of tenscile strength in gi-ven on) paes 15-17, withen illustration of the apparatus.

783. 'lew tester for taper (Perk.ins tensile tester). Pulp Paper Mnag.Capada 20, no0. 18:LOI(May 11, 1922); Paper Thade J. '74, no. lC':47(Anril 20,3-922).

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The Perkins tensile tester is of the vertical type, hydraulicallyoperated. The cylinder is filled with a liquid which is compressed bya solid mental plunger, which fits the cylinder with a very accuratelyground and lapped fit. This plunger is attached to the upper or station-ary clamp by eoans of a stirrup which brings the pull in a straight ver-tical line without cramping and without side pull. The lower or movingclamp is attached to a vertical screw vhich is operated by cars of a-

.--.-- - handwhcol on-the sidc of the machih5-'--Tn- pressure is indicated on aspecially radc standard gage vhich is acted on by hydraulic pressurefronm the cylilner. Rcnovablo and .intcrchangoable stop gages a-r -providedwhich nutor.ntica..ly separate the clamps 1, 2, or 4 inches aparb, asdesired, so that strips of those lengths may be tested easily. Theoperation of the tester is described.

784. Nose, Folix, and Sadlcr, Hars. Testing the stronth of paperwitl tlhe punctur dynanonoter of F. SchIubrt. Wochbl. Papicrfabr. 64,

no. 21:360-3i3(May 27, 1933); C. A. 27:5971; T. S. 98:14; B. I. P.. C.3:271.

The Schubert puncture dynanomotor is used in the textile industryfor strength testing of fabrics, the test being a puncture of the shoot

by a plunger or bolt of definite dimensions. The authors compare the

application of the now instrument and of the Schoppcr tensile tester

to papers and pulps of various boating degrees. Unbeaten stocks show

greaterr fluctuations in results with the Schubert tester; however,

uniform results arc obtained in the use of well-beaten stocks. Tables

showing results with the two testers on papers of various compositions

ore given.

785. Oliver, Cyril V. Variability in results net with in paper

strength testing. World's Paper Trade Rev. 93, no. 8:660, 662, 714; no.

9:754,, 756, 758, 796, 798; discussion, no. 11:938, 940, 942, 994, 996,998(Fcb. 21, 28, lMarch 14, 1930); Paper Makers' Mo. J. 68, no. 3:103-

109(.iarch, 1930); Paper-Maker 79, no. 6:595, 597, 599-605(June, 1930);Proc.' Tech. Section, Paper Makeors' Assoc. Gt. Britain Ireland 11, part 1:

53-74; discussion, 74-84(0ct., 1930); B. C. A. 19313B:582; C. A. 24:

33656, 5484; T. S. 92:157.

The electrically driven Schoppor tensile tester was studied. The makers

stipulate 100 iri. per -iinutc downward movement of the moving jaw. The in-

strul-cont is capable of adjustment to four different longtha of strips;

weights are supplied for readings up to 14 and 70 pounds, respectively. A

strip 5 cm. long gave higher results (8.2, 8.5, 15.1) than one 18 cm.

iong (5.1, 7.5, 13.3). The use of different weights for testing paperswith a tensile strength of less than 11 pounds gives rise to snall

differences in the results; the large weight gave slightly higher results.

in c series of tests on kroft paper the naxi.mun deviations were 5.6, 2.8,and 7.3^, and the avoraoc deviations were 2.2, 1.2, and 2.9%, respectively.

786. Paper Makers' Ansociation of Great Britain 8: Ireland. Tcchni-

cal Section. Poper Tosting Committee. First report. London, TheAssociation, 1937. 85 p. Also issued, with discussion, as Vol. 18,

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Tensile Strength P

port 1A, of' thoe Procoeding~s of twhe Technical Section. Sea also Worl(I's

Pdpor ZhradoeRev., Tech. Convontion to-., I46ioh, 1937:It-72; B. . P. C. 7:350.

Speci1fications are g3iven for the tenasilu t~ot using the Schoppcrtester. Thei tensile strength test gives a geoneral indication of the qualityof noner rather than definite information as to its suitability for any

- - - - - - npcfif toproe.- csnt cessary tvbaso-the test on eny.-fundaor--nontal consuiderati1ons o.r relate it to rrthods used for the tensile testingif other rmterials. The -iiediote roquircnents for a satisfactory spec1-

- fication arc that it sh2all be convenient to -apply, allow of reasonablespeed of testing, be of suitable sensitivity, and give consistent results.

Tetesting condfitilons (e.g., rate of 1.oaftiig) should either be the samefor different breaking 100(18 or else continuously variable. The factorneost difficult to snecify, is the rate at which the load, shall be applied.The tine rnay be shortened by usin L hohevier weiTght, (and. correspondinglyfLoro rapid rate of'laig for papecrs ovecr 14 pounds, -tho ratio being,,1:5. 'The effect of' thle changec in rate~ is not very clearly known butnublishod. results indicate that a definite change in strength con beintroduced. In the presentt, specification, twhe ratio of rates of loading

is3:5 (that is, thec weight is Live tines greater but the speed is re-d-uced to a thirC.). A change of rate of loading with the normal typeof instrui-ent can be obtalned, in the following ways: Bly using one clampspeed and different positions of' the weight on the arm; by flaing a constantspeed and. a ,-weater ran-e of' weights, (e.g., in the ratio of 1:2:3:k:5);by ~:irga single eu qc and. different speeds; or by a combination ofweig1hts and sneoeds. Thesev aru discussed. Results rer given which showthe tendency- of the strength to rise when measured on a shorter strip;their are not sufficient, however, to establish a correction factor and.,in any case, varying, uniformity in the paper may be expected to affectthe relation-shin. Similar results are obtained from single strips andfolded strips, the rmagnitudoe of errors being of the samec order in. eithercase. Stubstaintially the same results are obtained. whether single or

rmlt~tlicshets ore used. In the, ease of tissue paper. Present datai-dicato that small vori-inions in,~ the rate of loading do not affect theresults. The results arc expjressed as pounds breaking strain, kilogrambreaoking, utrair2 (calculated for 1 inch or 1 cm. width) or breakinglcnrelth in merters.

787. Physical testing of popor--tennile strength of paper. Tiring'sP-ener Zmster 1, no).. 2:1<4,(19356).

The tonsil:- strength of paper is the load required to break a parallelstrip of a stated width (usually 15 un). The arbitrary conditions ac-cenDted on; standard nrc: (1) that the test be carried out at 700 F. and

I' ®;'~" relstiv.c; ln:utdity on strips norcviously conditioned in that atmos-phere. (2) That both endse of' the strip for test be cJlamped in jaws -suchthiit the strip, icuigthe clomped ends, lIe 'InaI one plane. (3)That the tensile load, be tipplied along the center line anti in the nlanoeof thle strip. (4) rfllat thle distance between the edgeso of the jaws, or theactual lenJ,th of strip, under test, be 130 rn. (for pulp sheets, 100 at.).

(5) That thle tennsie xoad be gradiually increased at a practically unri--forna rate til.l fractlure o ss (6) That the load be applied at sucha rote thnt fracture scours in, about 20 seconds. The tensile test

Lloax~ac le'ss conniex: sot of proportion than. most other tests; the

Tensile Strength 2l

result depends primarily upon, and is almost proportional to, the basis

weight of the shoet; it also depends upon the degree of bonding between

the fibers; to .saon extent. on the average fiber length, and to a minor--extent upon the flexibility of the fibers and fibrous structure. The

boCt strips must be cut accurately parallel and with clean edges. For

un accurate test at least 10 strips should be cut from both machine and

crosc directions of 1C sample shoots of paper. There are four typos of

inoetruments: spring balance indicator, load applied by lever; hydraulic-diphragr.-and gage indicator, -lead applied by screw; inclined planetypo; pendulum (standard) typ.' This first type is represented by theSchopper portabtR instrument; the second.type is the Perkins instrument; -the inclined plane type (developed for textiles) has been adopted for

paper testing by the Scott Co. The last is particularly adapted to thegraphical drawing of the stress-strain curve and fatigue curves. A home-made apparatus is described also.

788. Radleggcr, Max. Paper testing with the Schubert puncturc-dynamometcr. Wochbl. Papiorfabr. 64, no. 39:685-687(Sept. 30, 1933);C. A. 28:1529; T. S. 98:296; B. I. P. C. 4:63.

The construction and operation of the apparatus (Noso and Sadler,

Wochbl. Papicrfabr. 64:360-363(1933)) are briefly criticized. By making

certain (not stated) changes in design and taking proper account of thedeflections, the results obtained with either strip or round samplesmay be calculated to tensile strength with reasonable accuracy. The

sample must have negligible stiffness.

789. Rcnnici;c, Norbert G. Manufacture of paperboard. Chicago,

Fibre Containers, 1939. 47 p. Chapter of paperboard testing in Fibre

Containers 24, no. 9:20, 22, 24, 26, 28, 30(Sept., 1939).

Tensile strorgth. This test is applicable only to single pieces of

paperboard.. The oamplcs are 0.5 to 1.0 inch wide and of such a lengththat, when cllaped. ir' the testeor, the distance between the jaws will

not be lceo than 5 tincs nor more than 12 times the width of the sample.

Thne can3pl is clorped scuaroly between the jaws of the tester and a

strlcscing frcc o:' 12 i:ichcs por minute is exerted; the point at whichfailure occurs is recorded. Tests in which the sampi.e breaks at or inone o0' the j.'cr a'r.: disregarded.

70C. Ru'r.emn:n, Fcitz. felf-recording strength tester. Papior-

'Vbr. 25, no. 577:51(1927); T. S. 89:167.

The R!hClcmann apparatus for determining the tensile strength andelasticity of single fibers photographically is described.

791. Schopper, Alfred. Apparatus for testing the tensile strengthof flexible materials. U. S. patent 1,797,734(March 8, 1929); J. Tex-tilo Inst. 22:A642.

A. apparatus for testing the tensile strength of flexible materials

^ ~by inflation, comprising moans for supplying gas under pressure to one

'. ~ side of the part under test and exchangeable means of geometrically- *' simrilr configuration for holdirg said part.

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Tensile Strength22

7¶.Schopper, Alfred. Determination of' the marginal strength-o- f paper and board. Papiet-rabriK 38:157-162(i94o); C. A. 355316;B. I. P. C. 11:210.

Experiments were carried out with a Schopper torsional ctrengthtester. A square test sheet is subjected to torsional strain, operat-ing at the two outur edgesa, through -t-wo ba-lanced forces which are vertical to the axis of the test shoot end which effect a marginal

ter i rslsi atrina oet(termed the "marginal moment"- ,whchisautonatical-ly mceaured by arccordine device, From this the

Eithr coot~hicmos takn aoneor considered in conjunction with'

value for marginal tothicu- tflou othtetsetthconcept of Lerug-bar" has boon avoiOded.

79.Schoppor, Alfred. Schopper's rapid paper tester. VereinsZellstoff U. Papiereiiemikor, Itouptvorsain-lunr, 1911:48-53; Wochbl.Papierfabr. 43, no. 2:94-96(Jan. 315, 1912); Papior-Zltu. 37, no. 5:140&

lh(ion. 13, 1912).

An illustratecd description is given of the rapid paper tester andits operation.

194. Schopner, Alf'red, and Dalen, Gustav. Apparatus for testingtensile strength. U. S. patent 1,819,719(Auge. 13, 1951); T. S. 94:280.

A Mullen-type tester is provided w-ith an elongation indicator con.-sisting of a pointer mounted on the shaft M' a pulley around which passesa thread, one end of' which is connected to a plate- restingr en a testpieces and the other end of which is cenorocted to a. coiunterweight.ThlIectrisal or mechanical means arc, provided tc apply a brake to thepulley when tlio test pioce bursts so) as to automsatically arrest theindicating pointer.

(95. Scheppor'si strength tester as a rapidL testCing apparatus.Panierf-nbr. 12, no. 17:-431-J-82(April 24, 19Th); ef. no. 20:577(May 15, 1914); Puilp Paper Mag. Canada 12, no. 12:575(June 15, 191.4).

A cormnlete strength test with thec Schopper apparatus occupie scon-siderable tinec in anay cases. The following ranid method affords, asufficiently exact test. aut only one stbrip from each direction of thepaper to be tented, add the two breaking loads (in gS. ) and divide bythree times the weight per square meter in. grams. In. order to obtainthe breaking strength in meters, the number obtained =ist be rultipliedby 100,000. Possible errors ca-)narise owning, to only oneo strip instead-of five being used, and thereby obtaininC. Lin ave-rageC which is notsufficiently exact. In) addition, the percentagec of moisture in. the~pener is noat taken into considcration. Since the~ moisture at 65%relative humidity is ThetwOen 7 rind 10%1, tho reslts -of thle teats willbe about 55 to- low. The formula on whiich the nbo;-cU test' is based is

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796. Schubert, Fricdrich. Cloth puncture strength tester. Leipzig.Monats. Text. Ind. 45:307-308, 347-349(1930); J. Textile Inst. 22:A155-

A description is given of an electrically driven dynamoetor inwhich the local strength of fabrics, paper, etc., is determined. Thetheory and practical value of the test and the calculation of the ro-.ults are flrthordiscussed. -

797. Schubert, Friedrich. Local examination of the tensile strengthof textiles, rubber, etc. A new method inf placo of the ordinary tearingtest. Cheou.-Ztg. 52, no. 94:913-915; no. 104:1018(Nov. 24, Dec. 29;1928); 55, no. 14:134-135(Fcb. 18, 1931); British patent 301,-24(Nov. 24,1927); C. A. 23:1187, 4103; 25:2025.

The fabric is weighted by a bolt producing a fissure of only afew rn. The new process is rapid and exact; it is very economical onaccount of .the suall size of the fissures, thus enabling one to donumerous tests with a snall amount of material. Cf. Radleggor, Wochbl.Papiorfabr. 64:685(1933).

198. Schubert, Friedrich. Method of and arrangement for examiningthe local strength of fabrics, paper, rubber, and the like. U. S.patent 1,836,621(Doc. 15, 1932); T. S. 95:75.

The principle of the invention consists in cutting a hole in thematerial to be tested, hold under tension in all directions, in the maintesting direction at both sides of and close to the sides of a pressuretool, and subosquently allowing the tool to operate on the severed piecesecured against sliding. Thie test is carried out with a pressure toolof rectangular cross section, which is provided with cutting edges ex-tending beyond those cnd of the to-l and corresponding in width to thesiz- of the pressure tool. The test piecc is placed in a special clampwhich is mounted in place of the bottom clamp of a tensile-strengthtostjr, ond the pressure tool is suspordid frou the chain of the upper

799. Scott, Henry L., & Co. Combination tonsilo tester. Instruments3:477-478(1.930); J. Textile Inst. 22:A313.

The combination tester for paper, etc., is built on the "dead weight"principle. The pendulum swings on ball bearings. The force exertedthrough tleo s3anpo raises tho pondulun, the pull in pounds being indicatedby the pointer on the dial. The toothed rack is one inch wide with teethspaced 12 per inch. Six gravity pawls travel on this rack and hold thependulum in the position at break until reacet by raising the pawls andrcturninig the pendulun to the vertical position. The stretching screwoperates smoothly and posses t!urough thec coar box without revolving.This obviates hie possibility of the yarn becoming entangled in theL'.)ving parts. 'Tc nmachino is operated by two lovers, one for startinganor.d the other for rororcing and atopping. The automatic reversing andstopping of the machine is accomplished by moans of an arm attached-to the stretching screw and sliding on the reverse stop rod between twoadjustable collars. Theo jaws nay be set at any desired distance apartand after each test the machine vill automatically reverse and stop otthe original starting position.

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Tensile Strength 2C4

800.- Scott, Henry L., & Co. The incline plane principle as usedin Scott testers. Paper Mill 59, no. 38:24(Sept. 19, 19356); B. I. P. 0.7:52.

The most accurate-method-oftesting-fatigue,"-tcrsiil-e, elongatio n,.-...--.----... ,r other pulling stresses is by applying load to the specimen itself

at a constant and uniform rate; the older machines, however, -applied---------- the tension-to- the samplA-in Vorying amounts per unit of time. The

incline plano principle used in the new testing machines applies adefinite amount of load per unit of time, regardless of whether thesample is long or short, elastic or rigid, ductile or plastic. Greateraccuracy and simplicity are claimed for machines of this type.

801. Scott, Henry L., & Co. Tensile testing machine calculatingattachment. Instruments 3:467(1930); J. Toxilo Inst. 22:A314.

The attachment comprises a weight adjustable on the balance armof the tensile testing machine, making possible a direct reading onthe dial in accordance with correction factors of- ny predeterminedtable.

802. Sindall and Bacon. The strength of paper. Testing twopieces at once. World's Paper Trade Rev. 59, no. 22:1001-1002; 60,no. 7:297-298; no. 10:437-438(May 30, Aug. 15, Sept. 5, 1915); Paper 12,no. 1:23(Juno 18, 1913).

Using a standard Lounig machine, tensile strength results were ob-.tnincd of a writing paper (16.5-lb. domy) by testing from i to 10 strips

- t the sa.er tinc. The results calculated for one strip from the ob--. sserved results wreo: 7.5, 7.25, 6.67, 6.45, 7.2, 7.1, 7.2, 7.1, 6.8,*1 'and 7.2. The results seen to indicate that the strength readings are

proportional to the number of strips; the average of all readings is7.05 pounds, whereas that for a single strip is 7.5 pounds. The gradualaddition of one strip for each succeeding c.pocriomnt does not appeal'

1¶ to create any serious difficulty in manipulation, as the averagereadings with the greater number of strips are fairly constant. Thesecond article shows that similar results are obtained with a woodpulp paper (6-lb. deny); the breaking weight of the paper found bytesting a oiurbor of single strips was 3.J, vwlereas the average of allthe readings was 3.G2. In the third article the effect of stretch isdiscussed. If two strips of equal length and width arc inserted inthe Lcunisg machine, one being taken from the machine direction and theother from the cross direction, it is clear that, when the tensionis gradually applied to both, thc mnchino-direction trip, thoughstronger, will break first because it sti'ctchc:; loss than the other.The weight necessary to break tho former is largely used in merelystretching the cross-direction strip.

805. Szoice, Paul, and Fra'nkel, Oscar. Brealrin strength andelongation. Papier-Fabr. 33, no. 25:213-214(June 23, 1935); B. I. P. C.6:378; T. S. 103:192.

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-- - With reference to-an earlier study by' ci .o, the authors show thatneither breaking strength nor elongation alone defines the qualityof paper or its resistance to mechanical stresses, but that both factorsarc required for determining these properties. They illustrate theirtheory by graphs and mathematical formulas.

.. ..-- -- - 80_ 4 TAPPIT. Tensile breaking strength of paper and paperboard.TAPPI Standard T 404 m-44. 1 p. Paper Trade J. 83, no. 11:53-54(Sept. 9,1926); 86,.no.-8:215(-Fcb. 25, 1928); 102, no. 8:133('cb. 20, 1936)-;112, no. 6:33-34(Fob. 6, 1941); Toch.. Asoc. Papers 19:271(Junc, 1936).

805. TIAPP. Tensile tester testing board. TAPPI Special ReportsNo. 1:81-82(1926).

The question discussed related to the use of tensile testers forcoarse boards, chci, as jute lincrs. Of the nine mills replying, only oneusc( the tonsilc tester; this mill stated that the test was of value in0cCtoirainirg diffterriccs between machine and cross direction; however,the test is inconveni.nt and slow to perform. It is doubtful if thetjnailc test is as useful as the Mullen for the routine and controltesting of boards. .Anothor mill reported thc use of the Perkins tensiletester for corp3aring the strength of various boards from 0.2 to 0.5inch blut did not us -it for mill control because the desired informa-tion was obtained with the Mallon tester. The tensile tester was usedfor dry felts for the manufacture of prepared roofings.

806. Tensile paper tester (Marshall). World's Paper Trade Rev.75, no. 5:k68(Fcb. 4, 1921); Paper Trade J. 75, no. 3:40.

Tho machine dep-nds for its action on the compression of the liquidcontained in thc diaphragm, the pressure being produced in the diophrnsnby nooan of a tensile force applied tlirouh the paper by a hand wheel.Thile pressre is roGistcrod on a dial in-term of the weight applied tothe strip of paper under test and the tensile strength is expressed inthc nurbcr of pounds pull which tle strip of paper supports up to thepoint of break; an inportant advantage of the lachino is that the ton-silo strength in 'oth the nnchine and cross direction can be dotcrEincdwith cqual oasc and certainty; another advantage is that the width andlcCgth of the strip nay be varied at will, the rachinc being capable ofdealing with strips up to 12 inches long and 2 inches wide. The stretchof the paper under tension is indicated on a graduated scale under theleft-hand screw clip, front. the rcading of which the percentage of stretchnay be readily ascertained.

1925).

Of 46 mills having telsilc testers, 19 used the Standard Schopper,'-advuatocd : in . oadLl14 in pounds; 2 used the Rapid Schopper (pounds);7 used the Perkins tostbr (pounds); 10 the Scott (pounds); 1 the3ickleo (pound:;); anl i hcd its o paper is primarily a dis-cucsion of the quostio;:. -f graduation in pounds or kilogramI. For com-morcial or m.ll wor- the pound was greatly favored.

' s^ ^ -- ', '- ........... '-~ffi ,M "filf.nr, -. ' ' 71'/' .*. *.1 1:il.:Y1tS ,

Tensile Strength 28e

808. Tensile testing machine for cellophane, transparent paper,etc. Silk & Bayon 13, no. 6:468(June, 1939); B. I. P. C. 9:487.

An illustrated description is given of a testing instrument for_ .. -. _ _. ac-.curatoly._determining-the _b-ea!ing-strenRth and- e longation-of-c ello--- ._....-

phane, transparent paper, and similar material. The machine is of theinclination balance type with a roller for the weight lever housed in

- - -'ino-ball bearings and"in'whhich-the medium fromrth ujppor grip tod . . --

t le indicating motion is a-flexible steel tape. - -

80. Thwing-Albort Instrument Co. Thwing-Albert clectrohydraulictensile strength tester. Circular M-388. n. d.

Illustration and very brief discussion.

810. Wernce, A. W. Manufacture of fibre shipping containers.Chicago. Board Products Publ. Co., 1941. 70-p.

Tonsile Toster. The tensile test, despite the several conditionsspecified, is one of the least arbitrary tests for the strength of paper-board and measures a less complex set of properties than most other testsin common use. The results depend primarily upon, and are almost pro-portional to, the basis weight of the sheet. They also depend upon thebonding between the fibers; to some extent, on the average fiber length,and, to a minor extent; upon the flexibility of the fibers and fibrousstructure. In general, the test results parallel those from the Mallen-tcct, but the latter, in addition to the factors mentioned, are also -grcctly influenced by the ability of the paperboard to stretch duringthc test. The tensile strength of paperboard is the load or weight,usually expressed in killograms (1 kg. = 2.2 lbs.), required. to break aparallel strip of a stated width, gcrerolly 15 mm. (19/2 .inches). Thearbitrary conditions accepted as standard are: (1) That the test becarried out at 70° F. and 5'% rolet.i.vc htumidity'on strips previouslyconditioned in that atmosphere; (2) 'iTlat both ends of the strip fortest be claupod in jaws such that the strip, including the clampedends, li-s in one plare; (3) That the tonsile load be applied alongthe center line and in the plane of the strip; (4) That tho distancebetween the edges of the jaws, or the actual length of strip undertcct, be 180 mm., except for pulp test sheets, for which 100 mm. isthe standard distance; (5) lTat the tensile load be gradually increasedat a practically uniform rate until fracture occurs; (6) That the loadbe applied at such a rate that fracture occurs in about 20 seconds.The tensile test is very widely used to define the "strength" of paper-board. Although it takes longer to perform and requires, as a rule, amore expensive piece of apparatus than the ITullcn or Cady test, it isbetter dofi.cd , is less empirical, and is a more roprodvcible test.As rnost tensile testers also incorporate a mechanism for determiningthe percentage stretch of the paperboard before rupture, at the camotime the tensile test is madc,. a knowledge of both may be gained withoutappreciable additional work. Itchl more information is then availablethan from the bursting strength tect only; norc especially if the two

Ue only poispcia ly if the twoI

Tensile Strencth 28'7

properties of' tens ile strength and. stretch are determined in both the

machine (grain) and cross directions of the board. There is no informs-

L ion given by, the bursting test which may not be deduced from the te-n-

sile and stretch tests; cornegquently, for scientific work, the latter

-- -- te~~bsts are tuch rfor:2i The ratio between the tensile tests in, the

p%Žqh e nu cros 41-cc bir5 rve useful information regarding the mannol:

in witch the~ she ol'; of' panerbonrft has been s.ade, and occasionally this

rncmosusot~s~acoptrl~teu-for-board. -no~Ide-on cylinder mnchi-nes,---

or w-ith a Wourdrinier, 0or adjusting the shake and other fmeters eon-

trolling, the un4

formity of strength in both directions.

Wet Tensile Strength

8'll, ~AdI'-to W. E., a C. Measitromemnt of' wet. strength.

Foret Poducs Lboratoriese of Canada, Quarterly Rev. Rbo. 4:12-17

(Oc1t-Lee., 1,930). Processed.

A preliminary report i s -'ivanr of a method. for determtining; the wet

strength. of puln test sheets. The sheet is made on the English -sheet

machine, and pressure I's applied at any one point on the sheet. The sue-

Mosn built up by the recsistance of sheet, is measured on a manometer. As

soon as a sufficient suction is built up, the sheet bursts;. the pressure

at that point re-,presents the breaking point of the sheet. The maxim=

reading on. the r-an~ometer indicates the, strength of the sheet. No further

information about this test seems to have been published.

-812. Fineh, J. M~. Weot strehgth tester for paper. Bell Labs. Record

IC), no. 1O:309(June, 194l); D. I. P. 0. 11:417.

A 5eteip of paperis In looped under a horizontal rod. in anl assembly

which :a i.old b, the own jaws of a papecr testing moonhino. AThe two

ern"! o;' the 1oo+) are elaLalpout in the u-~pper jaws. Below the rollis a container

filled vith waterv which canL lie~ ra~isedf so as to irnorse the paper. The

o-anrora uo gives rel~nlcti -c sul-ts in wet strengthtests en wekonneimons

Lnuc` ccn absorbent nrapY- and alsao on very thin tanper like that of Condensedr

rjsewhc is,, only 0.0003, Inch 7m th-icknes~s. The1 test is important

in i>:eas rf eoui).r used fxW? making phenol fiber.

K3-I. eeE0. otrivR tile strength of paper when vet.

Pt"PC19, no. li:15-l6(Novw. 22, 1.91-6); J. Imd. - Thig. Chera. 8, no. 11:

i005,-lO,'i4(Nov., 1,916); Papcr'likers' Mdo; J. 55, no. 2:hi4-46(Feb. 15,

bIQ1); Chen. i~h.24, no. 5.23!-236(may, 1917); C. A. 11:99.

The wet strength is determined by, break~'ng a strip of a definite width,

nf rte it ha beenm iwe1rsed in waiters at a constant temperature, for a definite

neOriol of tine. A Schoppur tensle trength maloichie is used. The jaws

ci' the elanw should open in front, so that -the ends of the wyet strips,

naty be inser-ted. without injury, and ore sot 10 cm. apart, ns a short strip

01 wetl npapr can be handled noer easily. The test strips are cut 15 .

j

Wet Tensile Strcenth 288L"

wide and. sufficiently lonC, to allow for clamping in thcnnchine. Thestrips are placed. sep-arately in a water bath at 700 F. for 20 mainutes.-After the specified, tirle they are renewed. one at a tine and tested.

strips to prevent injury~ to~, then. Date are civen showng'n thle effectof tci~oreratre of the -u> (I0 65,) 70, 75, and 1000 ".) and. of thetime -oftwtting-(l0; -2073:cL -6%0 nhfr. TPh6 toWs wF dbovslhi&2~-

- - - ---- tbs~tud~v-bluerririt papm-, !. Wet strength <--IF controlled by thec combina-tierl. of factors hiT1ch iaJ-x'nc~c-o other -physticalI properb.ien, such cs fiber leng,-th, beating., kind and qimslity of siz-ing, artd formation of The sheet,yet there~ is no direct relationship between the wet and dry strengthsof tuner.

E14. TAPPI. Commi-fttee on Paper Testine. [Tensile1 or breakingstrengthi] . Paper Trande j. 75 om. th4-b-45,(,July 27, 1922).~

DlRsuusono of' the Shopiopor tensile teetor. Wet tensile- strengtUhis also discussed.; Athe strips care ±nrnersea in water at 7Q0 F. for 20mIinutes and, a speed of C in~che~s per minauteo is applied. to the lower jaw7.

81.5. TPGPT. Wet tensile~ breaking strenGth of pare~r and paperboard.TKPPI sttncarl T 4i55 n 44. 1 sheet. ?tper Trade J.~ 115, no. 5:51-32,(Jul1y 50, 19~p42).

The ultina be wet strejng~th moans thle strength of1 the manterial aftercompleted s-aturation with a liquid. Iqornali wet strength means the strengthof the nsabarisl af tar it hsbeen wetted te an. extent compiarable withnormaal use conditions. For certain materials, such as tiussue mid unsized.

raosthe two ma.-y be the acre. The. apparatus consists of a tersilebutr(ci. T :0l4-n), and! a Finch we-teghdevice. The te-st is; made

aecndirCULg 'ho TK~rn Standard T ~,04 ml-n, sing~ strips thant have been wettedin li`qmudo t2 it The Fie tie Ig:-. E12] is usd o:? -,etting

raters Jj,~' are difficult to enil II webo. For ulbnt cttrength-0a-CV0 '110UI. -10.2 - nz

dUte'rnine the required UtiicA nTzwi' -m5 by i-rouln0 uQst 3t-L-p forvariouso rzeridos A' timunie sddt:on hi t ensile s-trength at the endof each period! u-ntil n.o i.thr igifcnt loss in tensile streongthocus To obtain normal wet strength valUes thL ieo meso

for papecr toweols shall be' 15 + 5 seconds cr1 Per, bluern)~int and. otherph~otocruphic papers 20 + 2 rtteusing water in~ ccch case.

289

WATER ABSORPTION

816. National Bureau of Standards. Structural fiber insulatingboard'. -3rd -ed. Corre.ercial-otndard CS42-43. 1943.

Water Absorption. .A specimen 12 x 12 inches-shall be dried at-1600 F. for 24 hours and colped to roon temperature in a dry atmosphere.The thickness of the sample shall be measured and the volume calculatedtherefrom. The sample shall then be carefully weighed and submergedhorizontally under 1 inch of distilled water maintained at 70 + 5° F.After 2 hours of submersion, the sample shall be stood on end to drainfor 10 minutes, at the end of which tine the excess surface water shallbe removed by hand with a blotting paper or paper towel and the sampleirmcdiately weighed, the volume of absorbed water calculated, and thewater absorption expressed in percentage by volume based on the initialvolume.

817. National Rcsearch Council of Canada. Procedure for makingphysical tests of fibre building board. IRC-19-1940(tontative). Jan. 31,1940. 2 p.

This method is the sane as that given by the National Bureau ofStandards.

8138. TAPPI. Water absorptivenoss of nonbibulous paper and paper-, board. TAPPI Standard T 441 n-42. 1 shoot.

This enothod is based upon the method of Cobb and Lowe CPaper Trade J.9c, Do. 12:43-46(March 22, 1934)] and Cobb [Paper Trade J. 100, no. 16:42-45(April 18, 1935)]. It is suitable for dotcrmining :etor penctra-tion into paper and board 0.004 inch or moro in thiclnoss. In the testa definite area of one side of the specimen is wet uniformly at the momentthat the count of time is begun. Penetration occurs only through thetest area and no possibility exists of wetting the edges or other portionof the specimen other than the area under test. The absorption of wateris stopped at the end of the test by removal of all surface water. An.accu-rat, jirht of' the specimen ic. obtained bofore and after cxposuroto tIhe watur. Loss of roiriturc between the cxpiretion of th;: tost periodand the tilo of wcishpin i's avoided. A suitable apparatus and procedureare described.

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AUTHOR I1l'TFDB

T~t:The nurnbers refer to the nuntered. entries in thle bibliography andnot to the paoe numbers.

Abbott,. F. -F., 483 -Abol, J. G., 1, 496Abrams, A., 67, 156), 157, 177Adams, F. WA, 590PAlington, W. E., 811Ainslie, P. A., 68, 178, 377, 655,

726;2-.e.xandor, 0., 81±ArLloricon Instrument Company, Inc.,

422r~,flcrictfn Society for Testing Moteri-

als, 2, 71-73, 133, 134, 179, 179A294-293, 340, 363, 378, 379, 389A,395A, 423, 4a4, 529A, 656, 657, 72

Ames, B. C., Co., 2991znther Testing Instruneont Co., Inc.,

135, 180, 300, 425;. 728"alderoon,, B., 658Anderson., L. C-, 74Aono, T.; 75Ape0 igren, C. E., 173PIrendt, A., 729

ryM., 110, 143, !144, 226Arxnold, L. K., 76, 132;.rnoul1, E., 750AXSOCiation. Of !Americar Railroads,

i4cYrs, L. R., 540

Bechnran, P.. P., 1'7].D~cor, 150, 267', 65a, 802Ba'iley, A,. J., 426 -

Bairtil r. K., 3, 32, 90, 1.26, 162,262, 567

Bard, P., 110Bardeen, -14. D. , -427Barnhart, 4. W., 550Barr, G., 77Basberg, A.-, 752Beunwucker, W-., 550Beach, P'. L., 182, 530-532Beadle, C., 183Bcazlcy, W., 551Bekck, J., 78, 79, 341, 552,, 553,

551, 592Ilellowc, J., 590

folentson,- C., 554 -Berco-vitz, D.,.4 3 o, 497Bercsi, J. Gt,733Bergene, E., 659Berndt, K., 431, 593, 594Best, A. S., 124Bevan, E. J., 9Bialkowsky, H. WT., 498Bidwell' P. Wi., 184Bierott, G., 185Blanchard, F. C., 186Blikoted, F., 596, 597, 7rBlum, R. J., 352

7 Bode, H. L., 380,5381Bo"MCke, H., 679Boernor, Ch., 187, 773Booth, Hi. 0., 660Boyce, D. H., 584Bragg, A. 0., 595Bray, G. P. R.,1 613Brecht, w., 555, 556, 596,

663, 736Brown, D. S., 159Brown, P. W-, 301.Brown, T. M., 598Brush Developmaent Company,Bmrgetanllor, P., 188

6

597, 661-

557

Campbell, J., 0oCampbell, P., 514, 55Camapbell, W. It,- 192, 737Canadian Pain and Paper Association,.

302, 382, 738Carlson, T. A., 353, 354, 364, 408-

410, 5142, 643 Carpenter, L. A., 1111, 443Carrier, ii. H., 432-Carson, F. T., 4, 5, 47, 56', 57, 81-

(- -156, 138, 193-1.95, 303, 304,5~87, 4119; 433, 483, 504, 512, 599,664, 665, 739

Carson, R. W., 305Carter, E. C., 600Case, H. u,., 666Chaplin, C. 4., 6Chttsor, 1H. "I., 67

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Author Inftox29

Instrument Sp)ciolties Company,The., 517

Isnard; R., 610, 767, 763Ivanov, N. D., 105)

Jacobson, P. M4. H., 22, 25, 456,oil, 686, 687

Johann, G. A,., Sfl 1, 1jL.Q, '221,-769

Jahn, E. C., 25, 412-Jarrdll, T. D., 60Johonsson, D., 6j88Jones, C. H. in?., 573

Kontroiwitz, M'. S.Y 26, 52, 574Kaplan, A. B.,50Katz, D. L., -1691., 359, 1414}Collor, E. L., 32Kioly, H. u., 61, 173, 457, 458Kionzl, HI., 459, 770Kirchner, E., 460, 406., 771lKirkwood, 1k. S.; 57, lsS, 504Kooster, !B., 649K~orn;' B., 513Korn;' it, 271-31, 463, 772, 775Kott,'H., 575-Xotto, -- , 612xoznrovitzlki7~, L. A., icfl

ixrU""Ucbzmr, '4.,% 141, 142Krauss, P. A., 109Krona, 0., 62, 222Krossler, J. P,,- 165

LbBntt, W. D., 225-225Land~t, G. E., 77ThLorocquo, G. L., 506, 576

Larson, L. Cr., 4-12Latham, J., 5~Thnudon;)ak, -T., 70'

theme, TI., 10, 1'-, 'lac, 226LitleU1c, J. R., 3)67!,odge, B.C., 0227Joo)bo, IR. 14~145

memo, VT. B., 14Loft'- n, R.- . 228~, -77

Lortz' ,~ cntCoLtl, 1

Lucy, '-T 6-I

McCarthy, J. L., 4.12McoCready, D. 17., 10,' 359," ;13, 4114

l~ceoP. i.,63

Mackin, G. E., 52McKinley, R. W., 216, 752MvNoughton, C. C., 222Malcoltinon, J. D., 229-233, 520, 368

Mnlott, iE,689Mulotrom, E. B., 559mann1 -K., 650 o Moncgol&, E., 112, 113M~arinti, M., 507Marsh, M4. C., 114Martin, R. I., 613Marx, Rk. J., 689, 690Masten, 'R. A., 80, 577, 614Il~oglitz, U1. B., 464, 465

-Mosnomr, it. 2., 234, 466, 777Monosmr, 1I; E., Ltd., 322micoua, Ti., 11,5, 6-15, 778M-i'llr, D. R., 316M-inor, C. A.; 616Minor, J.'E., 533 247, 616, 724,MOnzingtr, W. M., 467M~v.honcn, R. J., 617

NodII;,691Nao'imof; K.; 469UnounofP Tm 470 lnational A'scociction of Purchn~in~3

A~xontn, Inc., 235, 525, 569, 399,471', 6541, 692, y1 o

atmotinol flacoCreli Council. of Canada,4153, 5o8, 81747

Thoumnarn, 141., 474-47

Nluwll Tn, J. T"A, h00Nichols, 1.B, 9'5iBoll, A., 116Hioss, F., 784

Oclnrent, C., 509Oliver, C. V., 238, 239, 696, 7y95Ondood, Hi. W., Jyr>, 166

onporl Makcrs ' Association of GroatBritain and. Ireland, 117, 146, 2410,2):1, --527, 478, 697, y(86

Paris, P., 37, 38Povlotto, KC., 277Feck~han, W. M ., 94

Peek', -R. L., Jr., 174i'oirco, E". T., 621Pcrkins, D. F., and. Sorn, Inc.-, 2421

C' ., 602

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294Author Index

T~inias Olsen Testing t-lnehino ColnpanY, Wci6dcnmu~iic, nI-; 753

375, k4 1I. I Ueili, S.LD., 53, 65, 540, 719-721

Toledo Soi 9 opn,15 enr V. 7,292, 351, 361, ,,C> olto~6 -.pajl 153 m ~ obor,, S. W., 509~

TorlonolacoCO., 154 576, 407, 529, 541, 546, 7202, Smo

Thins, V -155oloS 1- 0Tma, v., '5I) - - ~~~~~~~~~~~11~' ,t Ic `O7

Tj. S. Anrk- Nnvy, 281, 359, 395-c. . Nojtional )3ar~COu of' 2torndards,

236-257, 324, 4w,2 4y,717, 731,Y82, 861

Vonduro Lkko, J5

Vran Kourcn, Co ., 553' -

VnughaNl L.$ Jr., 640Voitch,- F. m., <48'45 Yonnotmn, F., 223', 284

Wibilin, S., 718\T~tor L.B.,64

W otlib ot J. 700

Wc ht 4. W, 286-290Wate~(r, C. G., 516-51B~[0u i z jf f , B. L., 52-, 50j4

Wi ~7-linfl, ' S- 33., -5 -587 723-----

WITIinBs Apporotus-CO.,. 5kz

Wilson, E. G., 559Wilson, K. F., 362

Wilson, T. R. C., 400)

Wiptiorbottom, -M1., 72,4Withcrn; a. s.,~ Jr., 641.Withom, G. S., Sr., 725Worthington., F. V., 84,

599

Young, j. H., 432

Zipkicl2, G. S., 5P39

vsI

BS5 194, 195,

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