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147 The early history of lost-wax casting Christopher J. Davey ABSTRACT The different processes of lost-wax casting are described according to the technique used to form the wax model. The current assessments of the early history of the technique are discussed. The evidence from early literature, the moulds and metal artefacts are described and lead to the conclusion that lost-wax casting was a common process in much of the ancient world from the time that copper metallurgy was first developed. The development of the proc- ess begins with solid wax models in the late 5th millennium and ends with skin of wax models for life-size statuary formed by the ‘sloshing’ method in the classical period. Its origins are therefore much older than previously thought and its geographical spread is broader. The moulds show that lost-wax casting was often used for simple prosaic tools and ornaments and complexity of shape is not a determining feature of the process. In the ceramic cultures of the ancient world, lost-wax casting was not an exotic process used for complicated and prestigious items; in fact, the opposite seems to be the case. The construction of heterogeneous moulds with a gradation of clay coarseness aimed at preserving details on the wax model begins during the 3rd millennium BC and mould fragments displaying this variable fabric may be expected in the archaeological record. Introduction Lost-wax casting is acknowledged to have a long and con- tinuous history, the origins of which have generally been traced to 3rd-millennium Mesopotamia (Penniman 1975: 144). However, recent discoveries and research have revealed that this view was premature. Unequivocal evidence for casting practice comes from the discovery of the moulds used but, as lost-wax moulds are shattered as part of the process, they are not common. Broken unused moulds currently known are from Tell edh- Dhiba’i (Davey 1983, 1988; Al-Gailani 1965) and Poliochni (Bernabò-Brea 1964: 591, pl. 85d; de Jesus 1980: 41). The large number of used lost-wax mould fragments found at Gussage All Saints, Dorset, England from the pre-Roman Iron Age represents the only example of such material with published analysis (Foster 1980). This lack of evidence therefore necessitates the physical examination of objects to determine the possible means of fabrication. The discovery of the Nahal Mishmar ‘Cave of the Treasure’ and the more recent examination of the objects has added another chapter to the history of lost-wax casting (Shalev 1999), as has material from Mehrgarh in Pakistan (Mille 2006). This paper aims to provide a framework for further research into lost-wax casting by drawing on ancient lit- erature and evidence from the moulds and objects asso- ciated with the process. Complexity of shape has often been assumed to be the determinant of the process, but the evidence discussed below would appear to question this approach. Also questioned is the exotic nature of the proc- ess itself. The process There are many descriptions of lost-wax casting in the lit- erature. The techniques described vary depending on the circumstances, as they are defined by the available materi- als, traditions inherited and the size and form of the object to be cast. It is common for historical comment to focus on one particular method and to ignore other related tech- niques. It is therefore necessary to outline the range of lost- wax casting systems. One approach is to classify the nature of the wax model. Wax models may be fashioned in a number of ways and may take a variety of forms: solid wax made by hand – suitable for a pin; solid wax encompassing a simple core – suitable for a mace-head; solid wax formed in a piece-mould possibly incor- porating a simple core – suitable for a shafted axe-head; skin of wax around a directly securable core – suit- able for a figurine; skin of wax around a complex core – suitable for statuary; skin of wax formed in a piece-mould that is swished around (the ‘sloshing’ method) – suitable for a life- size bust. Simple cores are those that produce a hole in the model so that the object may be hafted. Complex cores are those which carry much of the shape of the object, thereby reduc- ing the volume of metal required for the casting and hence • • • • • • Offprint from J. Mei and Th. Rehren (eds), Metallurgy and Civilisation: Eurasia and Beyond Archetype, London 2009. ISBN 1234 5678 9 1011
Transcript of The early history of lost-wax casting
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Theearlyhistoryoflost-waxcastingChristopher J. Davey
abstract Thedifferentprocessesoflost-waxcastingaredescribedaccordingtothetechniqueusedtoformthewaxmodel.Thecurrentassessmentsoftheearlyhistoryofthetechniquearediscussed.Theevidencefromearlyliterature,themouldsandmetalartefactsaredescribedandleadtotheconclusionthatlost-waxcastingwasacommonprocessin much of the ancient world from the time that copper metallurgy was first developed. The development of the proc-essbeginswithsolidwaxmodelsinthelate5thmillenniumandendswithskinofwaxmodelsforlife-sizestatuaryformedbythe‘sloshing’methodintheclassicalperiod.Itsoriginsarethereforemucholderthanpreviouslythoughtanditsgeographicalspreadisbroader.Themouldsshowthatlost-waxcastingwasoftenusedforsimpleprosaictoolsandornamentsandcomplexityofshapeisnotadeterminingfeatureoftheprocess.Intheceramicculturesoftheancientworld,lost-waxcastingwasnotanexoticprocessusedforcomplicatedandprestigiousitems;infact,theoppositeseemstobethecase.Theconstructionofheterogeneousmouldswithagradationofclaycoarsenessaimedatpreservingdetailsonthewaxmodelbeginsduringthe3rdmillenniumBCandmouldfragmentsdisplayingthisvariablefabricmaybeexpectedinthearchaeologicalrecord.
Introduction
Lost-waxcastingisacknowledgedtohavealongandcon-tinuoushistory,theoriginsofwhichhavegenerallybeentraced to3rd-millenniumMesopotamia (Penniman1975:144). However, recent discoveries and research haverevealedthatthisviewwaspremature.
Unequivocalevidenceforcastingpracticecomesfromthediscoveryofthemouldsusedbut,aslost-waxmouldsareshatteredaspartoftheprocess,theyarenotcommon.BrokenunusedmouldscurrentlyknownarefromTelledh-Dhiba’i(Davey1983,1988;Al-Gailani1965)andPoliochni(Bernabò-Brea1964:591,pl.85d;deJesus1980:41).Thelargenumberofusedlost-waxmouldfragmentsfoundatGussageAllSaints,Dorset,Englandfromthepre-RomanIronAgerepresentstheonlyexampleofsuchmaterialwithpublishedanalysis(Foster1980).
Thislackofevidencethereforenecessitatesthephysicalexaminationofobjectstodeterminethepossiblemeansoffabrication.ThediscoveryoftheNahalMishmar‘CaveoftheTreasure’andthemorerecentexaminationoftheobjectshasaddedanotherchaptertothehistoryoflost-waxcasting(Shalev1999),ashasmaterialfromMehrgarhinPakistan(Mille2006).
This paper aims to provide a framework for furtherresearch into lost-waxcastingbydrawingonancient lit-erature and evidence from the moulds and objects asso-ciated with the process. Complexity of shape has oftenbeenassumedtobethedeterminantoftheprocess,buttheevidence discussed below would appear to question thisapproach.Alsoquestionedistheexoticnatureoftheproc-essitself.
The process
Therearemanydescriptionsoflost-waxcastinginthelit-erature.The techniquesdescribedvarydependingon thecircumstances, as they are defined by the available materi-als,traditionsinheritedandthesizeandformoftheobjecttobecast. It iscommonforhistoricalcomment tofocusononeparticularmethodandtoignoreotherrelatedtech-niques.Itisthereforenecessarytooutlinetherangeoflost-waxcastingsystems.Oneapproachistoclassifythenatureofthewaxmodel.
Waxmodelsmaybefashionedinanumberofwaysandmaytakeavarietyofforms:
solidwaxmadebyhand–suitableforapin;solidwaxencompassingasimplecore–suitableforamace-head;solidwaxformedinapiece-mouldpossiblyincor-porating a simple core – suitable for a shaftedaxe-head;skinofwaxaroundadirectlysecurablecore–suit-able for a figurine;skinofwaxaroundacomplexcore–suitable forstatuary;skinofwaxformedinapiece-mouldthatisswishedaround(the‘sloshing’method)–suitableforalife-sizebust.
Simplecoresarethosethatproduceaholeinthemodelsothattheobjectmaybehafted.Complexcoresarethosewhichcarrymuchoftheshapeoftheobject,therebyreduc-ingthevolumeofmetalrequiredforthecastingandhence
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itsweight.Thesecoresmaybekeyedintotheouter(invest-ment)mouldthroughholesinthewaxandultimatelythecastingitself.Alternatively,theymaybesecuredwithmetalpins (chaplets) that become part of the final casting. The core material is often removed after casting so that theobjectishollow.Theskinofwaxmodelsproducedbythe‘sloshing’methodmusthaveacoreofsandorclaypouredinandbakedsolidwhenthemouldisheated.
Allthesetechniquesseemtohavebeenusedinantiq-uity.Beforetheinvestmentmouldisformedoverthewaxmodels,sprues,gatesandrunnerswillbeaddedtofacilitatetheintroductionofmoltenmetalandtheescapeofairatthetimeofcasting.Thedesignofthesefeaturesembracesmuchoftheskillassociatedwiththetechnique,especiallywheredelicateorlargeobjectsaretobecast.
The investmentmould formedaround thewaxmodelmaytakeanumberofformsdependingontheshape,sizeandcomplexityofthemodel:
simple–onepiece;onepiecewithacoresecureddirectlytotheinvest-mentmould;complex,wherethecoreissecuredtotheinvestmentmouldbymetalpinsorchaplets.
Theinvestmentmouldscanbemadeinasinglephasewherearefractoryclaymaterialislaiddirectlyoverthewaxmodel.Theymayalsobebuiltupinsuccessivelayersfromanumberofapplicationsofdifferentmaterials.Whenthemouldisheated,thewaxrunsout.Thetemperaturetowhichthemouldisheatedwilldependonthematerialsused;today600°Cisthecommontemperature.
General historical assessments
Moorey (1994: 271f.) claims that lost-wax casting waspractised in Mesopotamia from at least Early DynasticI (2900BC)on thebasisof thegravegoods fromKish.However,allofMoorey’sevidenceisderivedfromarte-facts,noneofwhichseemtohavebeensubjecttoexpertmetallurgicalexamination.
Ogden argues that lost-wax casting was practised inEgyptfromtheOldKingdom,butdoesnotciteanyanaly-sesthatwouldsupporttheclaim.IndeedheisnotabletoreferenceananalysisofEgyptianmetalworkforanyperiodthatwouldconclusively identify lost-waxcastingandhereliesheavilyonthe1927workbyGarlandandBannister(Ogden2000:157–60).
Bannister, aprofessorofmetallurgy at theUniversityof Liverpool, provided reliable comments on fabricationprocesses. Garland and Bannister (1927) note that mostEgyptianbronzestatueshaveaholethroughwhichcorescouldbesecured.Ironnailswerealsousedtosecurecores,butnotbronzechaplets.Coresarereportedtobemadefromblackenedsandwithsomeorganicmaterial.LargestatuesfromtheNewKingdomperiodhavelimbscastseparatelyandjoinedtothebodybymechanicalmeans(GarlandandBannister1927:39–54).Lucas(1989:221f.)providessome
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detailaboutEgyptianlost-waxcasting,buthisexamplesareNewKingdomorlater.
IndusRiverpracticeisattestedbythewell-known‘danc-inggirl’fromMohenjo-darodatingtotheearly2ndmil-lennium BC (Penniman 1975: 144: Marshall 1931: 345,pl.94).
IntricatelydecoratedChineseShangandZhoubronzesare now known to be the products of piece-moulds andnotlost-waxcasting(Smith1981:128).Earliercommenta-tors proposed that the fine detail of these objects must have beenproducedbylost-waxcastingbut,aswillbearguedbelow, complexity is not an indication of lost-wax tech-niques.ThereisageneralviewinChinathatlost-waxcast-ingwasnotusedbeforetheEasternZhouperiod.Thisisalsoquestionedbelow.
Branigan has assembled other evidence for lost-waxcastingintheAegean(1974:83).Thisincludestheuseofbronzemoulds,whichhebelieveswereforcastingmodelsthatmayhavebeenmadeofleadinsteadofwax,asevi-dencedbyanEarlyBronzeAgeshaft-holeaxe-headfromSamos(Branigan1974:pl.13,587).
Classical lost-wax casting has been discussed byMattusch (1996) in thecontextofdetailedX-rayexami-nationofbronzesculptureheldinNorthAmerica.TheX-radiographsrevealtheuseofbronzechapletsandarangeofmeansofassemblingthecompletestatueswhichcouldnotbecastinasinglepour.
Ancient and more recent sources
ClassicalsourcesonmetallurgyincludePlinytheElder’sNatural History,Books34–35,writtenduringthe1stcen-turyAD.PlinyprovidesacommentaryonfamousGreekandRomanbronzestatuesandtheirfabrication(Mattusch1996:29ff.).Hereferstolost-waxcasting,statingthat:
The first person to make a plaster likeness of a human beingfromtheactualface,andhavingpouredwaxon to [into] this plaster mould, to make final correc-tionstothewaxcast,wasLysistratusofSicyon,thebrotherofLysippusIhavementioned…Lysistratusalso invented the takingof casts from statues, andthispracticebecame sowidespread thatno statuesor figures were made without a clay model (Pliny2004:336f).
This is a description of the ‘sloshing’ method techniquereferredtoabove.Thetechniquereliesontheproductionofdurableplasterpiece-mouldsmadeoveramodelwhich,accordingtoPliny,maybeanactualbodypart,astatueoraclaymodel.Thisenablesthesculptortomakemultiplewaxmodels which, as Pliny said, may be modified.
Intheabsenceofanyevidencetothecontrary,Pliny’scommentmayreasonablybetakentoattesttotheoriginofthismethod.LysippuswasacontemporaryofAlexandertheGreatandissaidtohaveworkedforhim,althoughthereisnorecordofhimtravellingtotheEast(Mattusch1996:98).Thedevelopmentofthistechniquepartlyexplainsthepro-
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lific nature of classical bronze sculpture. Pliny’s comment about making corrections is significant. Prior to the devel-opmentofmodernfettlingequipment,itwaspreferabletoproduceacleancasttoonewithmouldjointsandimperfec-tionsthatrequiredlaboriousgrindingandpolishing.
Of medieval and Renaissance texts, VannoccioBiringuccio’sPirotechnia(1540)hasadetaileddescriptionof lost-waxcasting,asdoesBenvenutoCellini’sTreatise on Sculpture, first published in abbreviated form in 1568. Thefullmanuscriptwasnotpublisheduntil1857andgivesan account of the casting of Perseus and the Gorgon’s Head(Cellini1967:114–26).Alltheaccountsofmould-making by these writers describe the use of fine clays coat-ingthewaxmodelandcoarserrefractoryclaysenclosingthemould.
Thetechnicalaspectsofthelost-waxtechniquehavealsobeendiscussedinthreeearlySanskrittexts,theManasollasa, the Silparatna and theManasara, in thecontextofsolidorhollowcastingofidols.The12th-centuryManasollasadescribes themakingof lost-waxmouldswith a smoothpastemadebygrindingamixofclay,ricehusks,‘cottonseveredahundredtimes’andsalt.Thepastewassmearedoverthewax(thinenoughtobetransparent).Afterdryingfortwodaysasecondthenathirdcoatwereapplied,eachbeing thicker than the previous one (Krishnan 1976: 2).The16th-centurySilparatnaalsodescribesthemakingoflost-waxmouldsbyapplyingverysoftwetclaytothewaxfollowedbyacoatofsoftclayonceithaddried.Finally,hardclaywasapplied.Hardclaywasmadefrommaterialprocuredfromananthillmixedwithbrickpowderandare-canuthuskjuice.Softclaywasmadefromfourpartsofpotclayandtenofordinaryclay.Verysoftclaywassoftclaymixedwithcowdung(Krishnan1976:4).
Whilethesedescriptionspostdatetheperiodofinterest,theydoprovideaninsightintotraditionalpracticesoflost-waxcastingthatpredatetheuseofmodernmaterials,andtheyilluminatetheissuesthatareimportantforthestudyofthehistoryoftheprocess.Someofthesepracticesstillexistinthedevelopingworld(Feinberg1983:29–31).
The Tell edh-Dhiba’i mould
Telledh-Dhiba’i,locatedinthesuburbsofBaghdad,wasexcavatedbytheDirectorateofAntiquities,Iraq,in1965underthedirectionofLamiaal-Gailani(Al-Gailani1965).Acoppersmith’sworkshopwasfoundinthecourseoftheexcavation.Itsdateisconsistentwiththatofthesite,i.e.theIsin-Larsa and Old Babylonian periods, the first half of the 2ndmillenniumBC(Al-Gailani1965:33,35).
ApreliminaryreportofthesitecontainedcommentsbyW.WintonoftheScienceMuseum,London,whostudiedphotographs of the finds and identified the object with Field No.614/19asabellowsfunnel(Al-Gailani1965:38).Theobject was not considered significant enough to receive an IraqMuseumnumber(Fig.1).
In1977theauthorwasabletostudytheTelledh-Dhiba’icollectioninthecourseofwhichanumberofdiscoveriesweremade,includingthefactthat614/19wasalost-wax
mould(Davey1983).Mooreydescribesanddiscussesthematerialinsomedetail(1999:265–72).
Oneendofthemouldwasfunnel-shapedandtheotherwasbroken.Thebrokenendrevealedthatitwasmadefromat least two distinct types of ceramic: a fine cream-coloured inner layer and a coarser buff-coloured refractory outerlayer.Theinnersurfacewassmoothandhadtheshapeofashortpinwithaknobandprobablyasphericaltop.Theextent of breakage was not sufficient to allow the extraction ofthecastingandsoitmaybeconcludedthatthemouldsuf-feredanaccidentpriortouseandwasthereforeunused.
PinswithroundheadshavebeenfoundinEarlyDynasticgraves.The‘A’cemeteryatKish,forexample,hasanumberofpins,theroundheadsofwhichweredeemedbytheexca-vatorstobecast(Mackay1929:171,pl.40).ThiscemeteryhasbeenredatedtoEarlyDynasticIII(2500–2600BC)byWhelan(1978:96)thatisaboutcontemporarywiththeroyalcemeteryofUr.Thisreliablyatteststothisprocessoflost-waxcastinginMesopotamiaatabout2500BC.
ThecopperdaggerfromKishcitedbyMoorey(1999:271)foranEarlyDynasticIuseoflost-waxcastingisnotentirelyconvincing.However,therein-guidesofaslightlylater date, also from Kish, do seem to have characteris-ticsincommonwithlost-waxcasting(Watelin1934:33,pl.24).Theseobjectsaresimilar tothosefoundatUrintheroyalcemeteryanddepictedonthe‘War’panelofthe‘Standard’(Woolley1934:pl.92).Fromthisevidenceitcanreasonablybeconcludedthatthelost-waxtraditionrepre-sentedbytheTelledh-Dhiba’imouldwaswellestablishedinMesopotamiaatleast900yearsearlier.
Thecapacityofmoderntechnologytocreatewire-likeobjects can mask the difficulty of doing this by ancient mechanical means. The ease with which a round cross-
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Figure 1Adrawing(a)andphotograph(b)ofthelost-waxmouldfromTelledh-Dhiba’i.(Photo:C.J.Davey.)
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(a)sectioncanbeformedusingasoftwaxmaterialexplainsmuchoftheattractivenessoflost-waxcasting.Theshapethusformedmaynotbecomplex,butithassmoothcurvedsurfacesanditisthisfeaturethatisthehallmarkofobjectsproducedbylost-waxcasting.ObjectswithdelicateroundsectionssuchastheMohenjo-darodancinggirlareclassi-callost-waxcastingshapes.
The second important feature of theTell edh-Dhiba’imouldisitsheterogeneouscomposition(Fig.2).Theuseoffine and coarse clays reveal that the practices described by theSanskritandmedievaltextswereestablishedby1700BCinMesopotamia.Theattentiontothequalityofthecast-ing’s surface represents anadvance in the technologyoflost-waxcasting.
The Akkadian copper head
The Akkadian copper head of a king from Nineveh(Strommenger1964:405,pls22–3)(Fig.3)andthefrag-mentary copper casting of a standard bearer (Al-Fouadi1976) reveal that lost-waxcastingof large-scalestatuarywaswelldevelopedinMesopotamiainthesecondhalfofthe3rdmillenniumBC.Bothobjectsaremadeofcopper,andthuscastingtemperatureswerecomparativelyhigh.Aconsequenceofthismayhavebeenthegreaterthicknessofcopperwhencomparedtostatuesoflatertimes.
Strommenger’s (1985) analysis of theAkkadian headrevealedchapletsprotruding2.5cmontheinside.Theearswere made separately and are solid. X-radiographs confirm thatthehairlineswerechasedontotheobjectaftercasting.TheseobjectsrevealthatinMesopotamia,3rd-millenniumlost-wax casting technology had progressed to the pointwhereonlythelaststage,the‘sloshing’method,wasyettobedeveloped.
Nahal Mishmar objects
In1961ahoardofcopperobjectsdatingtotheChalcolithicperiodwasfoundinacaveaboveNahalMishmar,awadionthewesternsideoftheDeadSea(Bar-Adon1980).Intotaltherewere429objects:416ofmetal,sixofivoryandsixhematitemace-headsandonemace-headoflimestone.
A technical analysis has revealed that the objects aremadefromantimony-arsenic-richcopper,purecopperornickel-arsenicalcopper.Thesourceof theores remainedlargelyproblematic (Tadmoret al. 1995:143), however,highnickelcoppersare reported tobe found inartefactsfromUrandthisleadstosomespeculationabouttheIranianplateauasanorigin.
The ceremonial objects are reported to be cast usinglost-wax techniques over cores in single castings. Therewasnoevidenceofbivalvemouldcasting.Onlytwoofthepurecoppertoolswerecastsolid,buttheassumptionthatthesewerealsotheproductsofalost-waxtechniquewasnotexplained.Whererepairswerenecessary,theyweredonebycasting,notwelding(Tadmoret al.1995:144).
Shalev (1999) reports on a casting experiment of theNahalMishmarhoardatPangolinfoundry.Themace-headsweremadeoverawoodenstick,thestandardshadclaycoresandthecrownswereformedfromslabsofwax.Theclay
Figure 2Detailofthelost-waxmouldfromTelledh-Dhiba’ishowingitslayeredconstruction.(Photo:C.J.Davey.)
Figure 3TheAkkadianheadfromNineveh,2300–2159BC(fromIraq3pl.6,usedwiththepermissionoftheBritishSchoolofArchaeologyinIraq).
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usedbyShalevcontaineddungandgrog.Shalevmakesnocommentaboutthequalityofthemetalsurfaceachievedbythis approach, but he does comment that the final grinding andpolishingcouldbedonebyunskilledworkers,suchaswomenandchildren,becauseitisthemosttime-consumingaspectoftheentireprocess(1999:298).HealsoreportsthatasurfaceanalysisoftheceremonialNahalMishmarobjectsdetectedextensivegrindingandpolishing.ItappearsthatthehomogeneousmouldsusedbyShalevproducedobjectsinneedoffurthertreatment.
The Poliochni lost-wax mould
AnEarlyBronzeAgelost-waxmouldwasfoundatPoliochni(Bernabò-Brea1964:64,591,pl.85(d);deJesus1980:41,fig. 15; Branigan 1974: 82, fig. 4). The mould is for an axe-headandwasbrokenbeforeitwasused.Itismadefromcoarseclayandisreddishontheexteriorandblackontheinterior. The blackness may be the result of the firing of the mouldandthemeltingofthewaxmodel.
Themouldappearstohavebeenfoundinametalworkingcontext.Thedescriptionandthephotographofthemouldindicatethatitishomogeneousincompositionandthatitwouldhaveproducedacastingwithfairlyroughsurfaces.
Nodiscussionofthecontextoftheshapeoftheaxe-headcontainedinthemouldhasbeenofferedbytheexcavatorsorBranigan.Suchananalysiswouldassistinestablishingthehistoryoflost-waxcastingintheAegean.Themouldisabout1,000yearsearlierthanthatofTelledh-Dhiba’ianditseemstorepresentanearlierlost-waxcastingtradition.
Mehrgarh
BenoitMillehasdrawnattentiontocopperalloy‘amulets’discoveredintheearlyChalcolithic(late5thmillennium)levelsofMehrgarhinBaluchistan,Pakistan.Hereportedthatmetallographicexaminationestablishedthattheorna-mentswerecastbythelost-waxmethod(Mille2006).Theamuletsweremadefromcopperalloyedwithlead.Mehrgarhiswellrecognisedasacentreforearlypyrotechnologies.Thewaxmodelsoftheamuletswouldhavebeensolidandmayhavehadasimplecoreinserted.Thisisunderstandablythe first stage in the technology. Mille also draws attention tothe‘LeopardWeights’fromBaluchistan,datingtoabout3000BC,whichweremadeusingacomplexcorekeyedintotheinvestmentmould.
China
Withover100,000piece-mouldfragmentsfromtheShangdynasty capital ofAnyang, it canbe assertedwith someconviction that lost-waxcasting technologywasnotpartofAnyangmetallurgy.However,theinspectionofamaskdatingtothelateShangperiod(about1300BC),nowinthe
NationalMuseum,Beijing,indicatesthatlost-waxcastingmayhavebeenpractisedelsewhereinChina(Fig.4).
The mask was part of a sacrificial deposit discovered inSanxingduiPit2,Sichuan(InstituteofArchaeologyofSichuanProvince1999:197,pl57;Bagley1999:213f).Therearsideofthemaskstillhaspartsoftheinvestmentmouldattached to it.Thewaxmodelof themaskwouldhavebeenmadefromsheetsofwax.Theopeningswouldhavebeencutwithaknifeandinsomeplacesontherearofthemaskwhatmaybefalsecutsofthewaxarepreservedin thebronzecasting(Fig.5).Therewasnoevidenceofchaplets,buttheholesinthemaskmayhaveprovidedthenecessarysupport.
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Figure 4 A drawing (a) and photograph (b) of the mask fromSanxingdui.(Photo:C.J.Davey.)
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Also found in theSanxingduiPitswere4,600cowrieshells (Anon. 1999: 419). Possibly of an Indian Oceanorigin,thesemayhavetravelledalongthe‘south-westernsilkroad’toSichuan.Itisthereforelogicalthattechnologiessuchas lostwaxcouldhave travelled thesamepath.Anexaminationoftheobjectsfromthislocationinrelationtolost-waxcastingiswarranted.
Gussage All Saints, Dorset
About7,318piecesoflost-waxmouldwerefoundatGussageAllSaintsdatingtothepre-RomanIronAge.Radiocarbondating confirmed a date of about 100 BC (Wainwright 1979: 125–53;Foster1980).AccordingtoTylecote(1986:35),this is the first evidence in the British Isles of lost-wax cast-ing.Thelost-waxmouldswereexclusivelyforthefabrica-tionofhorses’bridles.ApetrologicalanalysisofthemouldfragmentsbyHilaryHowardisreportedinFoster(1980:39–45)andestablishesthattwobasicclayswereused.Thediscoveryofsuchavolumeofmouldfragmentsholdsouttheprospectthatsimilardiscoveriesmaybemadeelsewhereinearliercontexts.
Other evidences
At Byblos, a series of piece-moulds for fenestrated axe-headswasfound(Dunand1954:98,pl.184).Theseitemsshowednosignsofbeingusedforthecastingofbronzeanditisthereforeproposedthattheywereusedforthecastingofwaxmodels.Theshapeoftheobjectsindicatesadateattheendofthe3rdmillenniumBC.
Unidentified moulds and fragments have been found in theliterature.TherearetwoobjectsatThermithatmaybeunused lost-wax moulds (Lamb 1936: 121, fig. 37). The purpose of the objects was not determined, but they aresaidtobemadefrom‘coarseredware’,whichwouldbeconsistentwithbeinga lost-waxmould.Oneobjectwasunstratified and the other was in an Early Bronze Age context.
Two clay fragments found at Hazor, dating from theMiddle Bronze Age, may have been used for castingsomethinglikethehornsofabullandmayhavebeenpartofalargermould(Yadin1965:130,pl.96no.30,pl.98nos.30–31).Thedimensionsoftheobjectsarenotclear.Theattributionof‘crucible’seemsunlikely,buttheobjectdoesindicateametalworkingcontextandthedescriptionofthefabricascoarse,redandwithtracesofstrawisconsistentwithlost-waxmoulds.
Conclusions
Lost-waxcastingbeganintheChalcolithicperiodbefore4000 BC. The attestation of the technique at Mehrgarhpoints to an eastern origin, possibly on the Iranian pla-teau.The Nahal Mishmar material some 500 years laterreveals theexistenceofa large-scale industryusinglost-waxcasting.TraditionaltheoriesthatthetechniquebeganinMesopotamiaarenolongerviableasitappearsthatlost-waxcastingbegansoonafterthestartofcoppermetallurgyitself and well before the development of the Sumeriancivilisation.
ThePoliochniEarlyBronzeAgelost-waxmouldshowsthatwaxmodelsweresolidormadeoveracorethatwassecureddirectlytotheoutermould.Themouldsthemselves
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Figure 5DetailoftherearofthemaskfromSanxingduishowing(a)mouldremainsinthenosecavityand(b)possible‘falsecuts’originallymadeinthewaxmodel.(Photos:C.J.Davey.)
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werehomogeneousincompositionandmadefromcoarserefractoryclaythatwouldhaveproducedobjectsrequiringsurface enhancement by polishing and grinding. It alsoshows that by the beginning of the 3rd millennium BClost-wax casting techniques were known from India toEurope.
Atsomestageduringthe3rdmillenniumBC,morecarewas taken inconstructing themouldsso that thesurfaceof the casting would not require attention. A fine slip-like material, probably mixed with cow dung, was appliedrepeatedly to themodeluntila reasonable thicknesswasestablished; a coarse refractory claywas then applied tocompletethemould.ThistechniqueisdemonstratedbytheTelledh-Dhiba’imould.
Lost-waxcastingdoesnotappearintheEurasiansteppebeforethelateShangperiodinChina,orevenlateriftheaboveanalysisisnotaccepted.Elsewhereitwasubiquitousandwasusedforprosaicobjectswithroundedsurfacesaswellasmoreintricatedesigns.Theeasewithwhichwaxmodelscouldbeperfectedandaccuratelyreproduced,thusobviatingtheneedforpolishingandgrinding,madeitthemethodofchoiceformanymetalworkers.
CoressecuredbychapletswereusedinthecastingoftheAkkadianhead,indicatingthatcomplexcoresystemswereknownbyabout2400BCinMesopotamia.Egyptianstatuary of the period had the cores secured directly tothe outer mould. Chaplets are known in New KingdomEgypt.
Pliny testifies to the classical use of forming wax skin models in piece-moulds, and the analysis of statuary byMattusch indicates thatbronzechapletswere thenormalmeansofsecuringthecoresbythattime.Theonlyaspectoflost-waxcastingthatwasnotpractisedbytheRomanperiodwasthesinglecastingoflargestatues.Cellini’sdescriptionofthecastingofthethreeandahalftonnestatueofPerseus and the Gorgon’s Headimpliesthatthiswasrareeveninhisday.
The modern perspective that the technique wassophisticated ignores the fact that theancientworldwasasocietybasedonceramicsandthat theproductionofapotterymouldwasstraightforward.Smithisatleastpartlyrighttoviewthemetalworkerasrelatedtothepotter(1981:127). Modelling in a soft material and then reproducingthe shape accurately in metal circumvented the need tomechanicallyshapethemetal,somethingthatintheancientworld was difficult and time consuming. Lost-wax casting wasnotonlyusedforintricateshapesbutalsoforthoseofareasonablyroutinenaturethathadcurvedsurfaces.Inanerawhensystemssuchaswirepullingandextrudingarenormal,itiseasytoforgetthatobjectswithacircularcross-section were difficult to produce by primitive mechanical means.
The importanceof achieving a smooth surface of thecastingledtotheconstructionofmouldswithheterogeneoussectionsfromalmosttheoriginofthetechnique.Thevariableceramiccross-sectionoftheTelledh-Dhiba’imouldandthedescriptionsofmostoftheancientauthoritiesleadtotheconclusionthatlost-waxmouldsfromatleasttheMiddleBronzeAgewillnormallynothaveahomogeneousceramiccomposition.
Asnootherpotteryisformedinthismanner,thediscoveryofheterogeneouspotteryfabricsmaywellattesttolost-waxcasting.The shapesof suchmaterialwillbenondescriptandinthepastwouldhaveescapedtheattentionofmostarchaeologists who seek diagnostic forms and not significant fabrics.Untilmetallurgicalworkshopsareexcavatedwiththeprecisionofprehistoricarchaeology,manyoftheprecisedetailsofthesmith’stechniqueswillremainobscure.
Postscript
Afterthispaperwassubmitted,YuvalGorenpublishedapaperin2008entitled‘Thelocationofspecializedcopperproductionby the lostwax technique in theChalcolithicSouthern Levant’ (Geoarchaeology: An International Journal23(3):374–97)inwhichhedocumentsthediffer-ent clays used in the moulds associated with the copperobjectsfromNahalMishmarandotherChalcolithicsites.IamindebtedtoProfessorGorenforacopyofhispaperandthenewsthatacopperstandardrecentlyfoundatQiryatGathasamultilayeredmouldremaininginsidetheshaft.Thereisalayerofclayandgrassandalayeroflimeandquartzsand.Thisdemonstrates that therewasdiscriminationofclay types formouldingprior to the3rdmillennium, thepurposeofwhichisuncertain.
Acknowledgements
The author acknowledges the helpful discussions with CameronMcIndoeandSeanElliotofFundêreFineArtFoundryandStudios,Melbourne,andRichardStringerwhotaughthimbronzesculpture.
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ForewordbyWeidongLuo,Chancellor,UniversityofScienceandTechnologyBeijing viiForewordbyRobertMaddin,ChairmanoftheBUMAStandingCommittee ixPreface xiAcknowledgements xiiiListofcontributors xviiIntroduction xxi
Early metallurgy across Eurasia
AncientmetallurgyintheEurasiansteppesandChina:problemsofinteractions 3EvgenijChernykh
EarlymetallurgyinChina:somechallengingissuesincurrentstudies 9JianjunMei
MetaltradeinBronzeAgeCentralEurasia 17LiangrenZhang
Documentaryandarchaeologicalevidenceforanantiquecopper-nickelalloy(baitong) 26productioninsouthernChinaanditsexportationtoIndiaFrançoisWidemann
MetaltradebetweenEuropeandAsiainclassicalantiquity 35AlessandraGiumlia-Mair,MichelJeandinandKen’ichiOta
TheblackbronzesofAsia 44PaulCraddock,MaickelvanBellegem,PhilipFletcher,RichardBlurtonandSusanLaNiece
Bronze casting technologies in ancient China
OriginsandevolutionofthecastingtechnologyofAnyangbronzeritualvessels:anexploratorysurvey 55YuLiu
ThreeWesternZhoubronzefoundrysitesintheZhouyuanarea,Shaanxiprovince,China 62WenliZhou,JianliChen,XingshanLei,TianjinXu,JianrongChongandZhankuiWang
Newresearchonlost-waxcastinginancientChina 73WeirongZhou,YaweiDong,QuanwenWanandChangsuiWang
IncipientmetallurgyinYunnan:newdataforolddebates 79TzehueyChiou-Peng
Contents
METALLURGYANDCIVILISATION:EURASIAANDBEYOND
vi
AstudyofthesurfacecraftofweaponsfromtheBa-ShuregionofancientChina 85ZhihuiYaoandShuyunSun
ProductionofsignatureartifactsforthenomadmarketinthestateofQinduring 90thelateWarringStatesperiodinChina(4th–3rdcenturyBCE)KatherynM.Linduff
Ancient iron and steel technologies in Asia
Anearlyiron-usingcentreintheancientJinstateregion(8th–3rdcenturyBC) 99RubinHanandHongmeiDuan
FromwesternAsiatotheTianshanMountains:ontheearlyironartefactsfoundinXinjiang 107WuGuo
SouthIndianIronAgeironandhighcarbonsteel:withreferencetoKadebakeleand 116comparativeinsightsfromMel-siruvalurSharadaSrinivasan,CarlaM.Sinopoli,KathleenD.Morrison,RangaiahGopalandSrinivasaRanganathan
SurvivaloftraditionalIndianironworking 122VibhaTripathiandPrabhakarUpadhyay
Finestructures:mechanicalpropertiesandoriginofironofanancientsteelsword 129excavatedfromanoldmoundinJapan MasahiroKitada
Specialisationiniron-andsteel-makingintheearlyMiddleEastandCentralAsia: 134myths,assumptionsandareassessmentofearlymanuscriptevidence BrianGilmourAncient metallurgical and manufacturing processes
Theearlyhistoryoflost-waxcasting 147ChristopherJ.Davey
Anaturaldraughtfurnaceforbronzecasting 155BastianAsmus
Theliquationprocessutilisedinsilverproductionfromcopperore: 163thetransfertoanddevelopmentinJapanEijiIzawa
AtechnicalstudyofsilversamplesfromXi’an,Shaanxiprovince,China, 170datingfromtheWarringStatesperiodtotheTangdynastyJunchangYang,PaulJett,LynnBrostoffandMichelleTaube
Scientific analysis of lead-silver smelting slag from two sites in China 177PengfeiXieandThiloRehren
