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ARTICLE IN PRESSG ModelULHER-2476; No. of Pages 9

Journal of Cultural Heritage xxx (2010) xxx–xxx

riginal article

n site consolidation of burnt and partially charred wood in dry conditions

enedetto Pizzoa,∗, Giorgio Garabelli b, Michelangelo Varettob, Luca Emilio Brancatib,arina Locandierib, Elisa Pecoraroc, Nicola Macchionia

CNR-IVALSA, Istituto per la Valorizzazione del Legno e delle Specie Arboree, Via Madonna del Piano, 10, 50019 Sesto Fiorentino (FI), ItalyConsorzio San Luca, per la cultura, l’arte ed il restauro, Via dei Mille, 14, 10123 Torino, ItalyCorso di Laurea in Conservazione e Restauro dei Beni Culturali. Università di Palermo, Palermo, Italy

r t i c l e i n f o

rticle history:eceived 18 May 2010ccepted 21 September 2010vailable online xxx

a b s t r a c t

Forty years ago in a xxth-century church in Torino, a small fire partially burned some of the decorativeexternal boards of the sound-box of the organ. The focus of this present work was to find a treatment ableto consolidate partially burnt wood in dry conditions, in which the external charred layer would be lostif not well preserved because of its incoherence. The product had to be applied onsite on an architecturalstructure intended to be reused again (and not simply exhibited). This circumstance is rarely encountered

eywords:urnt woodarbonized woodharcoalbrasion testeuse

in the conservation of wooden Cultural Heritage. The efficacy of treatments was evaluated on the basisof a suitable and original experimental methodology, which took into account both the immediate andlong-term behaviour of the various tested products. Although the opportunity to carry out this workcame from a real case, both the selected product and the set up evaluation methodology have a generalvalidity and they can be effectively used in other similar situations in which a slight antipowdering effect

.

harred carving is required for treatment

. Introduction and research aims

Consolidation of charred wood in dry conditions is a relativelynused practice in the conservation of wooden Cultural Heritage,ssentially because burnt timber structures, even when partiallyharred, are generally dismounted and substituted. More expe-ience is available in the case of waterlogged charred material,ecause very often, these kinds of artefacts are found in archae-logical excavations and, therefore, acquire an historical value.owever, the know-how coming from these kinds of experiences

s in practice not directly transferable to the restoration of charredaterial in dry conditions because of the completely different

pecificity of the waterlogged charcoal. In fact, usually this latters completely filled with water at the moment of treatment, andherefore, impregnation is mainly governed by diffusion, whichs a very slow process [1]. Moreover, in archaeological excava-ions, wood can have a charcoal aspect but it is often only partiallyurnt. In these cases, the problem of decay by fungi and bacte-ia [2] has to be faced; therefore, there is no differentiation in

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he treatments used between the charred layer and the rest ofhe artefact. Conversely, degradation in dry charcoal is relatedo the effects of high temperatures developed during a fire onhe chemical components of wood cell walls. In fact, polysac-

∗ Corresponding author.E-mail address: pizzo@ivalsa.cnr.it (B. Pizzo).

296-2074/$ – see front matter © 2010 Elsevier Masson SAS. All rights reserved.oi:10.1016/j.culher.2010.09.003

© 2010 Elsevier Masson SAS. All rights reserved.

charides (both hemicelluloses and cellulose) are mainly lost athigh temperatures, and this implies a strong decrease in specificgravity and the modification of most of physical characteristicsof charred wood. In this perspective, the increase of hydropho-bicity due to enrichment in the aromatic fraction in dry charredmaterial [3,4] is one of the most important factors when consid-ering a subsequent treatment by consolidants, mainly if wateris used as the carrying agent. All of these reasons resulted in alimited research effort in facing the problem of consolidation ofpartially charred dry wood for onsite applications. A small amountof scientific work concerning similar issues is available, but itmainly concerns cases of findings of archaeological origin, in whichproducts are applied for immersion [5–8], or veneered furniture[9].

1.1. The case study

The Sanctuary church of Sacro Cuore di Gesù in Torino (Italy)began construction in 1872, based on a design by the ArchitectEdoardo Arborio Mella, aided by Count Reviglio della Venaria andby engineers Pulciano and Soldati. It was consecrated on the 31stof December 1876, although incomplete due to financial problems

of burnt and partially charred wood in dry conditions, Journal of

[10]. However, during the following years, the extension projectof the church was continued by Pulciano. The construction of theapse, which represented the final intervention of enlargement, wascompleted only in the period 1907-1911, following the design ofengineer Giuseppe Gallo. He also designed the refined and metic-

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2 B. Pizzo et al. / Journal of Cultural Heritage xxx (2010) xxx–xxx

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Fig. 2. Particular of the burnt surface.

natural colour of charcoal. These observations forced us to evalu-ate an alternative and original methodology of consolidating drycharred material, which was able to reduce the loss of surface par-ticles.

Fig. 1. Image of the artefact in an old brochure belonging to Negri’s workshop.

lous supplement of decorations and of fittings, of neo-gothicnspiration, still visible today [11–13].

The two-manual organ placed on the counter-facade wall wasonated by the widow of lawyer Giovanni Bassignana, and itas commissioned to the organ construction company Vegezzi

nd Bossi di Centallo on 1886 [11,14]. Afterwards, most proba-ly between 1886 and 1895 (definitely by 1907), the workshop ofasquale Negri, cabinet-making teacher at the Artigianelli trainingchool, made the wooden sound-box and the choir balcony. Thisork is documented on a lovely image of an old brochure belong-

ng to Negri’s workshop [15,16], but unfortunately, the precise datef execution was not reported (Fig. 1).

The organ sound-box and organ loft were partially damageduring a fire which broke out in the church on Christmas Eve of968 and also destroyed the baptismal font [14]. Flames devel-ped only on the right-side of the two wooden structures (chancelnd sound-box), close to the internal stairs of the balcony, and itropagated only on the surface front of both architectural elementsFigs. 2–4). However, despite the finishing of the external surfaceartially contributed to stir up the flames, the same finishing alsoave a kind of protection to charred layers below, thus resultingn a composite material constituted by a thin skin made of charustained by a thicker support made of wood in essentially soundonditions (Fig. 5). Recently, when some parts of the finishing wereccidentally removed the charred wood below turned to dust andence, it was lost. This made it imperative to find a solution for theonservation of the charred portion of the chancel (Fig. 2), in ordero avoid its crumbling.

A first attempt of consolidation was carried out by using acrylicroducts at very low concentrations (0.5–1.5% in butyl acetate).hese materials are commonly used for consolidation of incoher-nt and rotted wood, either applied repeatedly or in only one coat17–19]. However, this attempt evidenced an increased detach-

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ent of small char blocks in correspondence of the deeper burnedayer, because of the excessive weight increase of the treated exter-al charcoal layer. The use of acrylic resins resulted also inadequate

rom an aesthetical point of view because of the glossy and vitres-ent effect that appreciably contrasted with the characteristics and

Fig. 3. Particular of the burnt area and of the nearby one. Some surface damage isevident.

of burnt and partially charred wood in dry conditions, Journal of

Fig. 4. A capital involved in the fire.

ARTICLE ING ModelCULHER-2476; No. of Pages 9

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3.1. Physical measurements on char and microscopicobservations

A portion of the reference sample (Fig. 7) was placed in a humid-ity saturated environment at 40 ◦C for a month. The aim of this

ig. 5. Transversal profile of specimens. The charred layer of a few millimetres inhickness is visible on the upper part.

.2. Conservative requirements and aim of the work

Two needs arose from the considered conservative case:

the carbonized structure had to be maintained in its integrityas part of the interior decorative architecture, which assumes itsown added value thanks to its harmonic coherence with the com-plex and articulated series of all other fittings within the church;the structure had to be reused again as a functional organ andchoir, thus implying that people would access the balcony, andhence, there would be unavoidably contact and friction withsome parts of the charred structure.

The focus of this present work was, therefore, to find a consoli-ating product for partially charred wood in dry conditions whichould be applied onsite on an architectural structure that has toe reused again (and not simply exhibited). This circumstance iscarcely encountered in the conservation of Cultural Heritage ofooden objects. The evaluation was based on a suitable and orig-

nal experimental methodology, which took into account both themmediate and long-term behaviour of the various tested products.

Although the opportunity to carry out this work came from aeal case study, both the selected product and the set up evaluationethodology have a general validity and they can be effectively

pplied in other cases, involving the consolidation of charred woodn dry conditions.

. Conditions of the artefact

The sound part of the structure (part of the front, the wholeeft-side, the covering of the central portion and of the left tower)videnced signs which characterize an artefact from the beginningf xxth century in ordinary maintenance conditions: dust deposits,ocalized alterations of finishes and of surface protective paints,imited presence of shrinkage openings in some joints (due to theatural shrinkage of wood), deformations of minor entity, resinxudates, some ruptures in a few stress points of assemblage, andrequent (although limited) presence of insect attacks.

The state of preservation of the burnt portion and also of thatetween the sound and the charred wood (Fig. 3) was very different.n this intermediate region, the heat and flames licked the mate-ial without provoking its ignition. On the other hand, the charredaterial evidenced a thickness variable between 4 and 20 mm, on

oth faces of the wooden partition (the internal side and the exter-al one). This material and the carved decorative parts inserted intohe structures (Fig. 4) were better analysed in order to evaluate its

orphological characteristics.

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.1. Autoptical analysis of charred material

Starting from the external side, a first surface layer a few �mhick was detected on the char. It corresponded, in the sound

PRESSeritage xxx (2010) xxx–xxx 3

structure, to the layer treated with finishing and protective paints.This thin film, only partially adherent to the char, showed a seriesof diffused micro-wrinkling mainly localised on the perimeter ofsquare-shaped pieces which constituted char. Below this kind ofskin, the charred material was formed by a semi-structured crustof variable thickness, consisting in fragments of irregularly cubicform penetrated from deep orthogonal fissures. In addition, belowthe crust, a very thin layer (less than 1 mm) was evident. It wasdark-brown coloured, powdery and made of partially burnt woodand not totally charred, which represented the boundary layer withthe original wood, still in apparently sound conditions.

On the surface of the sector of the wooden structure involvedin the fire, some holes or gaps were observed. These holes corre-sponded to small squared particles, both in engraved elements andin wooden partitions, and they were due to accidental bumps ordetachments. By observing the holes, it was possible to reveal thatseparation always appeared in correspondence of the layer in con-tact with the unburned wood. An additional aspect related to thedamage on the burnt material emerged by inspecting the brokensurfaces with oblique light: some losses of the finishing layer (orig-inally treated with protective paints) emerged, thus resulting in aseries of small surface imperfections. They were due to abrasions,scratches, contacts or brushing, even of minor entity, which clearlyevidenced the very low mechanical consistence of the burnt mate-rial and the urgent need of its consolidation in order to avoid itsloss.

3. Material and methods

All experimental tests were carried out on specimens obtainedfrom a board taken from the lateral portion of the organ woodensound-box (Fig. 6). The board was representative of the gen-eral state of preservation of the material. Seven samples of size12 cm × 17 cm were obtained from the board, of which one wasused as the reference in the evaluation of the behavioural differencebetween the untreated material (as currently it is) and the treatedone. Samples evidenced a surface charred layer of a few millime-tres in thickness contiguous to wood in essentially a normal stateof preservation (Fig. 5).

of burnt and partially charred wood in dry conditions, Journal of

Fig. 6. Extraction of the board on which all measurements were carried out.

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Table 1Products and conditions used for treatments.

Number Consolidant Solvent Concentrationsused in tests

1 Aquazol 200 Water and ethylalcohol 80:20 v:v

7.5 and 10%2 Mowital B 60HH Ethyl alcohol

3.3. Treatments evaluation

From a mechanical point of view, the main problem that theactual material had to overcome was its tendency to pulverize, that

ig. 7. Portion of the sample used for the physical characterisation of the material.

rocedure was to reach an elevated equilibrium moisture contentithin test pieces, in order to take a measurement of total shrink-

ge that was as reliable as possible. After equilibration, two smalleramples were obtained (Fig. 8) with opposite sides oriented accord-ng to the three anatomical direction of wood: sample A with a

inor amount of charred wood and sample B with a much higherercentage of char. In addition, four smaller samples were obtainedrom the residual material and were used for measuring the mois-ure content of the material. Once the equilibration was reached, allhe small specimens were weighed and the edges measured, andhen, they were put in a oven at 103 ◦C until a constant weight waseached. As usual, this condition was considered to be the anhy-rous weight. The three edges were also measured at the anhydroustate in order to evaluate shrinkage.

Microscopic observations were carried out in order to both iden-ify wood species and evaluate the differences between the soundriginal wood and the charred one. The observations were exe-uted on a Scanning Electron Microscope (SEM, XL20 Philips) afteretallisation through gold-plating.

.2. Consolidant products and application methods

The products used for applications were among those, whichre usually utilised for the consolidation of decayed wood. Theirist and final concentrations of treating solutions applied on spec-mens are reported in Table 1. Aquazol 200 is a homopolymerf 2-ethyl oxazoline (2-ethyl-4,5-dihydro-1,3-oxazole). It is wateroluble, non-toxic and biodegradable [20,21]. Mowital B 60 HH ispolyvinyl butyral stabilised with polyvinyl alcohol. It is soluble

n organic solvents [22]. Regalrez 1126 is a polymer obtained from

Please cite this article in press as: B. Pizzo, et al., On site consolidationCultural Heritage (2010), doi:10.1016/j.culher.2010.09.003

inyl toluene and methyl styrene. It has low molecular weight andt is soluble in apolar solvents [23,24]. Cosmolloid 80 is a micro-rystalline wax constituted by a mixture of saturated hydrocarbonsith both linear and branched chains. It is also soluble in apolar sol-

Fig. 8. Particular of specimens used for shrinkage measurements.

3 Regalrez 1126 White spirit4 Cosmolloid 80 White spirit5 Paraloid B72-B67

90:10Amyl acetate(pentyl acetate)

vents [25]. Paraloid B72 and B67 are acrylic resins, copolymers ofethyl-methacrylate/methyl-acrylate and of isobutyl-methacrylaterespectively. They are well known in the wood consolidation fieldand can be considered as a reference among consolidating materi-als.

Considering the limited availability of material, only one speci-men for each concentration reported in Table 1 was prepared.

Products were sprayed in repeated coats, starting from a firstapplication of pure solvent finalised to increase wettability and pro-mote the subsequent spreading of products. After this first phase,consolidants were applied starting from solutions at concentrationof 2.5% and then of 5%, 7.5% and finally 10%. Based on preliminaryevaluations, in each coat a same amount of solution was applied,namely 150 g/m2. There was a waiting period in the order of a fewhours before applying the subsequent coat, thus allowing for sol-vent evaporation. The products application was carried out withsamples in a vertical position (Fig. 9), in order to simulate theapplicative conditions in the real workshop.

After the impregnation phase at 7.5%, samples were divided intwo portions (Fig. 10): while one part was kept as such, the finalcoat with the consolidant solution at 10% was applied on the otherpart. Afterwards, both portions were further divided in two parts,and therefore, four smaller parts (two treated with solution up to7.5% and two up to 10%), each one approximately 6 × 8 cm2, wereobtained at the end. Each of these four parts were characterisedas reported in the subsequent paragraph. In all cases, there was awaiting period of at least 15 days from the products application toits characterisation before taking measurements.

of burnt and partially charred wood in dry conditions, Journal of

is to lose small particles in powdery form even after light contact.

Fig. 9. The various products were applied in spray with samples in vertical position.

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ig. 10. After the treatment with solutions up to 7.5% specimens were divided inparts, 1 of which was treated with a 10% solution.

esistance against abrasion was, therefore, chosen as the evalu-tion method for treated samples, by also comparing the valuesith that of the reference untreated material. This kind of test was

xpressly set up for this work, and it consisted in the evaluationf mass loss of samples after they were subjected to mechanicalubbing in controlled conditions. The abrasive action was exertedhrough a 42 mm diameter, 3 cm thickness foam rubber cylinderdensity 16 kg/m3), wheeled at a rate of 300 rpm under two levels ofonstant weight: in the first step, the load was 1 kg (±100 g), appliedor 60 seconds, and in the second step, the load was 2 kg (±100 g),pplied for 30 seconds (Fig. 11). The second step of the test was car-ied out on the same area, which had been already abraded duringhe first step. The effective application of the selected load on thepecimens’ surface and the constancy of the load for the whole test

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uration were preliminarily verified by using a weighing balanceFig. 12). All tests were carried out with a pillar drill.

In addition to mechanical tests, both the treated specimens andhe reference sample were subjected to a series of environmen-

ig. 11. Test configuration for measuring the resistance against abrasion of speci-ens treated with the various products.

Fig. 12. The verification of the load effectively applied on the specimen’s surfacewas carried out by using a weighing balance.

tal cycles, in which temperature was kept constant at 25 ◦C andmoisture was varied between 25 and 65% each 24 hours. A totalof 15 complete cycles were carried out in these conditions. After-wards, the duration of each phase was increased to 48 hours, and inthese new conditions, additional five complete cycles were carriedout.

4. Results and discussion

4.1. Physical and microscopical characterisation

Based on its anatomical characteristics, the wood was identified

of burnt and partially charred wood in dry conditions, Journal of

as Norway spruce (Picea abies Karst).SEM microscopy allowed observing an external, completely

charred, portion of wood (Figs. 13 and 14). It maintained theanatomical tissue typical of the species, but assumed a more frag-ile aspect (rupture was sharp and the section was more readable),

Fig. 13. Portion of wood completely charred.

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Fig. 14. Upper part in the figure, a portion of charred wood. Below, a less decayedportion of wood.

Table 2Equilibrium moisture content of specimens maintained in a water saturated envi-ronment at 40 ◦C.

Specimen MC (%)

A 23.2B 32.5C 21.8

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Table 3Physical characteristics of specimens.

Specimen Anhydrous volumicmass (g/cm3)

Specific volumetricshrinkage coefficient (%)

FD

D 20.8E 26.2F 34.1

aving thinner cell walls than normal. This occurrence can bettributed to the known fact that charcoal cell walls lose their typi-al organisation of different layers and become a single thinner andore fragile layer [26]. The advancement of carbonization appeared

n remission, or at least strongly decelerated, from latewood por-ions (Fig. 14). In fact, the use of a razor blade (used for preparingections to be observed) left an area less readable because of theifferent mechanical behaviour of the two portions of material.

Fig. 15 shows the various specimens obtained from the samplequilibrated in elevated environmental humidity conditions.

By comparing Table 2 and Fig. 15, it appeared that specimensith a higher presence of charred layer (B, E and F) reached

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igher equilibrium moisture content than the rest of the specimens.similar behaviour is evidenced also by decayed waterlogged

rchaeological wood, which loses most of its polysaccharides con-ent like in the case of charred wood [2].

ig. 15. Rear and front of six specimens obtained from sample in Fig. 7. Samples A and B w, E and F were only used for moisture content.

A 0.323 0.46B 0.268 0.29

Anhydrous volumic mass of specimen A was very close to typicalvalues of spruce in sound conditions (Table 3), whereas speci-men B clearly evidenced a lower density, due to a higher presenceof charcoal in this specimen. Specific volumetric shrinkage coef-ficient was reported instead of volumetric shrinkage coefficient,the former being the volumetric shrinkage percentage per unitmoisture content. This parameter also evidenced the appreciabledifference between the less and the more presence of charred woodin specimens. The lower volumetric shrinkage coefficient of sam-ple B directly derived from the higher moisture content reachedby the sample compared to the moisture content reached by sam-ple A. Moreover, the shrinkage of the important charred portionwas lower than wood, although char apparently absorbed moremoisture than wood.

4.2. Products application

During the products application, samples 1, 3 and 5 (treatedrespectively with Aquazol 200, Regalrez 1126 and the mixture oftwo paraloids) did not evidence particular inconveniences, evenfrom an aesthetical point of view.

Instead, sample 2 (treated with Mowital B 60 HH) evidenced asurface whitish layer at the end of the complete treatment process.This whitish layer was removed with a nebulised pure solvent. Also,sample 4 (treated with Cosmolloid 80) evidenced a whitish surfacelayer at the end of treatment process. Two different cleaning tech-niques were tested on the sample on which solutions up to 10%were applied. A part was treated with pure solvent, whereas theother one was mechanically cleaned by using a soft cloth (Fig. 16).The best aesthetical result was obtained by means of mechanicalaction, but this method can hardly be proposed in this specificcase because of the presence of small parts, which are not easilyaccessible (e.g. in capitals and carvings).

4.3. Mechanical and long-term behaviour of treated samples

of burnt and partially charred wood in dry conditions, Journal of

Results of abrasion tests are reported in Fig. 17 for samplestreated with solutions with concentrations up to 7.5% and in Fig. 18for those additionally treated with solutions at 10%.

ere used for measuring volumic mass, moisture content and shrinkages. Samples C,

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Fig. 16. Comparison between the two different techniques of cleaning used toremove the surface whitish patina, which appeared in specimens treated with Cos-molloid 80.

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Fig. 17. Mass loss of specimens treated with solutions up to 7.5%.

Please cite this article in press as: B. Pizzo, et al., On site consolidationCultural Heritage (2010), doi:10.1016/j.culher.2010.09.003

It is possible to observe that no appreciable differences betweenhe two concentrations existed for specimens treated with Aqua-ol 200, Regalrez 1126 and mixture of two Paraloids, whereas inhe case of both Mowital B 60 HH and Cosmolloid 80 the abrasionesistance worsened by increasing their concentration. However,

ig. 19. Comparison among specimens subjected to the abrasion test with a 2-kg loadeference sample. Centre: sample treated with solutions of Aquazol 200 up to 10%. Right:

Fig. 18. Mass loss of specimens treated with solutions up to 10%.

this difference can be attributed to surface cleaning needed in bothcases, as described above. In fact, in the case of Cosmolloid 80, thewhitish surface layer, which formed, was not removed in the sam-ple treated up to 7.5%, and this evidently protected the same surfacefrom abrasion.

Measurements evidenced some differences between the variousconsidered products. Regalrez 1126 showed mass loss practicallyidentical to that of the untreated charred material, as in the case ofsample treated with Cosmolloid 80 when the surface whitish patinawas removed. A similar behaviour was also observed for Mow-ital B 60 HH: when the anti-aesthetic surface whitish layer whichappeared after treatment was removed the mass loss raised from0.05 g (2 kg/30 sec condition, sample treated with solutions up to7.5%, whitish layer not removed) to 0.14 g (2 kg/30 sec condition,sample treated with solutions up to 10%, whitish layer removed). Atthe end, the product evidencing the lower values of mass loss afterabrasion was Aquazol 200. In Fig. 19, the comparison among threespecimens (the untreated reference and two samples treated withdifferent products) is shown along with the related foam rubbercylinders as they appeared at the end of the tests.

Also, the exposure to environmental cycles evidenced somedifferences among the various samples. After the tests were con-ducted, the untreated reference sample lost a great part of theburnt protective paints that constitute the surface film, thus con-firming once again the need for an intervention (Fig. 20). Samplestreated with Aquazol 200, Mowital B 60 HH and the mixture of twoParaloids did not evidence any distortion, cracks, colour changeor aesthetical alteration. Instead, in the specimen treated up to10% with Cosmolloid 80, the whitish patina which was previouslymechanically removed partially appeared again. The specimen

of burnt and partially charred wood in dry conditions, Journal of

treated with solutions up to 7.5% remained unchanged in its whitishappearance. Finally, both samples treated with the Regalrez 1126solutions showed a series of white small spots on the surface(Fig. 20).

maintained for 30 seconds and of related soft plugs used in tests. Left: untreatedsample treated with solutions of Cosmolloid 80 up to 10%.

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ig. 20. Specimens after the exposure to environmental cycles. Left: untreated refeith Regalrez 1126 up to 7.5%. White little spots appeared on the surface after test.

. Conclusions

The partly charred material coming from the Sanctuary churchf Sacro Cuore di Gesù in Torino allowed characterising andreating the interesting composite material, which was consti-uted by a layer of charred wood of a few millimetres thicknessn close contact with a substrate of wood in an apparent goodtate of preservation. As for the characterisation of this mate-ial, the physical-microscopic analysis showed that the equilibriumoisture content of samples containing more charred wood

esulted higher than those containing less char. This fact wasttributed to the strong difference in morphological and physicalharacteristics between these two aspects of the same mate-ial. Moreover, the easy powdering of substance experienced inormal conditions (e.g. after accidental contacts) was confirmedy the elevated fragility exhibited by samples under observa-ion.

Concerning the treatment aspects, a quantitative criterion ofvaluation based on non standard abrasion test was considered.his kind of test was specifically set up for this circumstance, con-idering the peculiar problems of the case and the unavailabilityf other relevant methods for an efficient evaluation of treat-ents. The results of environmental cycles were also included in

he evaluations. Tests evidenced an appreciable difference amonghe various considered consolidants, with Aquazol 200 being theest performing product for both concentrations considered (solu-ions up to 7.5 and 10%, applied on more coats). In additiono abrasion tests and exposure to environmental cycles, otherspects were also considered, such as easiness of application, sol-bility in water, a lower degree of toxicity, absence of removalor cleaning) operations after treatment and the aesthetic finalspect.

After the experimental phase carried out in the laboratory, theeal application of a selected product on a limited area of the arte-act has been planned. Afterwards, this area will be used to verifyhe effectiveness of treatment methodology in real service condi-

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ions after a predetermined period of time.Although the abrasion test set up in this work was mainly

ntended for the consolidation of charred dry material, it could belso used in other similar situations in which a slight antipowderingffect is required for treatment.

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sample. Severe detachments of surface layer were observed. Right: sample treated

Acknowledgements

We thank Simona Lazzeri and Lorena Sozzi, CNR-IVALSA, whocarried out SEM analyses and took the related photos.

References

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