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Treating friable matte pigments on bark:experimental analysis of four consolidantsKate L.M. Beckera

a Archaeological Conservation, c/o Museum of London, 150 London Wall, London EC2Y5HN, UKAccepted author version posted online: 20 Jun 2014.Published online: 15 Sep 2014.

To cite this article: Kate L.M. Becker (2014): Treating friable matte pigments on bark: experimental analysis of fourconsolidants, Journal of the Institute of Conservation, DOI: 10.1080/19455224.2014.928644

To link to this article: http://dx.doi.org/10.1080/19455224.2014.928644

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Kate L.M. Becker

Treating friable matte pigments on bark: experimentalanalysis of four consolidants

Keywords

Aboriginal bark paintings; conservation; matte pigments; friable pigments; consolidants;JunFunoriw

IntroductionFlaking and friable paint has long been noted as a condition concern of col-lected ethnographic art and material culture. Over the years, variousmaterials for the consolidation of friable matte pigments have been rec-ommended, from resins to commercial fixatives and varnishes. Thisarticle continues the investigation of appropriate consolidants for friableearth pigments specifically from the perspective of Aboriginal Australianbark paintings. The experiments described herein compared the efficacyof four consolidants in treating highly friable pigments on simulated testboards. There were three stages of experiment. First, the most effectivesolvent and concentration for each consolidant was determined. Next, theselected solutions were applied and the test boards monitored for surfacechanges. Finally, a series of abrasion tests were executed in order toassess the degree of consolidation achieved.

When considering consolidation of bark paintings there are numerousfactors to take into account. Therefore, the research does not necessarilylead to a definitive treatment or consolidant choice but provides more infor-mation on treatment options. Areas for future research are also highlighted.Some constraints of time and resources were unavoidable, as is the casewith experimental research.

BackgroundThe country now known as Australia has a long history of culturalexpression by a diverse group of people referred to as Aboriginal Austra-lians. The extant art discovered in caves dates to at least 50,000 years ago,making it one of the oldest artistic traditions in the world.1 There alwayshas been and continues to be a great diversity of land and culture bothbetween and within the regions of Australia and the associated islands(including Torres Strait Islands, Papua New Guinea and Tasmania); thus,the following background represents numerous generalisations.2 One ofthe prevalent traits of Aboriginal Australian culture is that of the ‘Dream-ings’ or ‘Dreamtime’. A European term,3 it can be defined as:

‘Dreamtime refers to the beginnings of time; it underlies the present and deter-mines the Aboriginal future. Dreamtime stories, reflected in art, tell the tales ofancestral beings who created the land and all its formations, and establishedtraditions and ceremonies. Importantly, these legends tell the story of a particu-lar region and the descendants of the ancestral beings who gave specific groupstheir land, and responsibility for its care.’4

Dreaming stories are the basis of the Aboriginal Australian cultures and arethe bridge between intangible and tangible heritage. These stories are com-municated by various abstracted symbols that belong to a language specific

(Received 3 November 2013; Accepted 23 May 2014)

1 Wally Caruana, Aboriginal Art(London: Thames and Hudson, 2003),2; Susan Lowish, ‘Setting the Scene:Early Writing on Australian AboriginalArt’, Journal of Art Historiography 4(2011): 1.

2 Richard Broome, Aboriginal Austra-

lians: Black Responses to White Dominance,1788–2001 (Crows Nest, NSW: Allen &Unwin, 2001). See Chapter One formore information.

3 Caruana, Aboriginal Art, 10.

4 Beata Tworek-Matuszkiewicz, ‘Aus-tralian Aboriginal Bark Paintings:Their History, Structure and Conserva-tion’, Reviews in Conservation 8 (2007):15.

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to the region and culture. Once the language is known to the viewer, the paint-ings can be read as stories or maps, transforming intangible heritage into tan-gible material culture. The subject matter and style of depiction of barkpaintings is also highly significant as it potentially identifies the region,tribe, and even the individual responsible for producing the work, as wellas the individual’s relationship to others, including his/her ancestors.5

Arnhem Land (North and West) is considered the centre of bark paintingproduction, in part because this region has a tropical climate that allows treesto grow successfully.6 Unfortunately, deterioration is pervasive in bark paint-ing collections. A contributing factor is that bark paintings, both historic andmany contemporary pieces, were not necessarily produced to last a longtime. Additionally, when bark paintings are removed from their productionsetting, changes in the environment can cause significant changes to the sub-strate and pigments.

Deterioration of bark paintingsThe original design of bark paintings did not take material life span intoaccount, as many bark paintings would have been destroyed or allowedto naturally decay after production. The impetus for collecting AboriginalAustralian art came after Western contact, and has resulted in a rising inter-est in permanently displaying bark paintings. Given bark paintings’ orig-inal intended life spans, it is not surprising that they experience a rangeof condition changes whilst in collections and museums. Bark paintingsare at risk of deterioration from many agents, including physical forcesand changes in relative humidity (RH), both of which then contribute todissociation of the bark painting from its intended meaning and values.7

One of the most prevalent condition concerns resulting from physicalforces and changes in RH is paint instability due to flaking and/or friability.Lack of adhesion of the paint layer to the bark substrate is often a result ofdimensional changes in the bark support, as the cycle of changes loosensthe bond between the paint layer and the bark, leading to flaking, tentingand eventually loss.

The inherent properties of the pigments and binders used can alsoexacerbate these issues. There are four primary colours used in traditionalAboriginal Australian art: black, white, yellow and red. Most commonly,the black pigment is charcoal, the yellows and reds ochres, and the whitekaolin clay or chalk. Often, the white pigment present on bark paintingsis the least well preserved. For chalk-based white pigments, this isbecause the particle size of the pigments is very small, so that thepigment forms a thick paste when mixed with binders. After the pastedries, the remaining chalk particles form a porous and poorly coheredlayer. Additionally, chalk is prone to absorb and desorb water cyclically,causing further structural instability of the pigment.8 The choice ofbinder also affects flaking and friability, based on the strength and stabilityof the substances over time. Additionally, there are bark paintings wherelittle or no binder was originally applied. A variety of commonly usednatural binders have been documented including orchid sap, turtle eggs,wax, tree resin, vegetable gums, water and bodily fluids includingblood.9 From the late 1960s, PVA (polyvinyl acetate) binders became com-monly available and used; the wood-glue Aquadherew was the most com-monly documented synthetic adhesive used.10

Various approaches have been recommended over the years for consoli-dating Aboriginal bark paintings from resins to commercial fixatives andvarnishes.11 More recently, methyl cellulose and gelatine have been advo-cated in low concentrations. Recent research has explored consolidantapplication using an ultrasonic mister while the object is under vacuumor in a solvent chamber.12

5 Caruana, Aboriginal Art, 21–60.

6 Caruana, Aboriginal Art, 21.

7 Tworek-Matuszkiewicz, ‘AustralianAboriginal Bark Paintings’, 17–8. Formore information on dissociation as anagent of deterioration see RobertWaller and Paisley S. Cato, ‘Agent ofDeterioration: Dissociation’, CanadianConservation Institute: Ten Agents of

Deterioration, http://www.cci-icc.gc.ca/caringfor-prendresoindes/articles/10agents/chap03-eng.aspx (accessed 15April 2014).

8 Tworek-Matuszkiewicz, ‘AustralianAboriginal Bark Paintings’, 18–9.

9 William Boustead, ‘Conservation ofAustralian Aboriginal Bark Paintings,With a Note on the Restoration of aNew Ireland Wood Carving’, Studies inConservation 11, no. 4 (1966): 199;Marion Ravenscroft, ‘Methods andMaterials used in Australian AboriginalArt’, Bulletin (Institute for the Conserva-

tion of Cultural Material) 11, no. 3(1985): 101; Beata Tworek-Matuszkie-

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The aim of the research presented in this article was to analyse the efficacyof four consolidants to adhere friable matte pigments to a bark substrate.

Analysing consolidant performance using simulated test boardsThe aim of the experiments was to better understand the materials and pro-cesses used when consolidating friable matte pigments on bark substrates.By applying selected consolidants to test boards with properties similar toAboriginal Australian bark paintings, those most suited to treating friablematte pigments could be experimentally identified within a similarcontext, without putting objects at risk.

1 Experimental methodologyThe number of variables that need to be accounted for in a comparativetreatment study designed to be applied to non-identical objects is plentiful.To reduce the number of variables, it was decided to make 10 test boards byusing one type of bark and applying the same pigments and binder in thesame manner to each board. Each would then be ready for the designatedconsolidant application. In this way, it was hoped that differences could beattributed to the different consolidants rather than differences in the sub-strate. The following outlines the type of bark, pigments, binders and con-solidants used in the experiments, and how the test boards were produced.

Eucalyptus tetrodonta is the most common species of eucalyptus used inbark painting due to its prevalence in northern Australia. However, thisspecies does not grow readily in the UK. Because of import restrictions, itwas necessary to use a different species of eucalyptus that could besourced in the UK.13 A large piece of Eucalyptus nova-anglica bark wasacquired from Lullingstone Castle, Kent.14 After acquisition, the bark wasair-dried and flattened. The bark was then cut into test squares with apower saw, each approximately 5 cm×5 cm (+1 cm). There were severalsignificant differences between the traditional techniques for preparingbark for paintings and the test boards, including that the boards were notflattened over heat, the boards were not allowed to season, and the exteriorbark was not stripped off. As the experiments did not include artificialaging or measuring changes in bark dimensions, these variations wereaccepted, as they should not have significantly affected the behaviour ofthe pigments or consolidants within the experimental timeframe.

The next step in the manufacturing process was pigment sourcing andpreparation. Red ochre, yellow ochre and carbon black ground pigmentswere readily available in the laboratory. Significantly, commercially avail-able pigments, such as those used in these experiments, are purified,whereas those sourced naturally are likely to have additional inclusionsand contaminants, the possible impact of which is not addressed in thisexperiment. A comparative white pigment was more difficult to acquire.The most common white pigments used in Aboriginal Australian barkpaintings are kaolin (a hydrated aluminium silicate) and chalk (calcium car-bonate with possible clay inclusions).15 However, a mine in WesternArnhem Land where 99% pure calcium magnesium carbonate can beobtained is also a known source for white pigment.16 For these experiments,the only similar component available was 98% pure calcium carbonate.Therefore, the behaviour of the white pigment on the test boards mostclosely mirrored that of chalk. Each of the four pigments was individuallyground in a cleaned mortar and pestle to remove any lumps before beingtransferred to a new container.

Next, each of the 10 test boards was arranged with the inner bark facingup and the fibres running vertically. Deionised water was mixed with smallamounts of each pigment in a paint palette until a paste-like consistencywas achieved. It is at this point in the process that a binder would normally

wicz, ‘Conserving Aboriginal BarkPaintings’, National Gallery of Australia:Collection Conservation: Object Conserva-tion, http://nga.gov.au/Conservation/Objects/bark.cfm (accessed 3 March2013), 3.

10 Tworek-Matuszkiewicz, ‘AustralianAboriginal Bark Paintings’, 19.

11 Tworek-Matuszkiewicz, ‘AustralianAboriginal Bark Paintings’, 21–3.

12 Tworek-Matuszkiewicz, ‘AustralianAboriginal Bark Paintings’, 21–3.

13 It is illegal to import non-manufac-tured wood and/or bark into the UKfrom non-EU countries. Border Force,‘Bringing Fruit, Vegetable and PlantProducts into the UK: Don’t Break theLaw, Check the Rules Before YouTravel’, UK Border Force Pamphlet, 2013,http://www.ukba.homeoffice.gov.uk/sitecontent/documents/travel-customs/bringing-plants.pdf (accessed 15 Decem-ber 2013).

14 The bark was acquired with the helpof Tom Hart Dyke at LullingstoneCastle. Lullingstone Castle is located inKent, England and is home to theWorld Garden of Plants and the NationalCollection of Eucalyptus. See http://www.lullingstonecastle.co.uk/ for moreinformation. The National Collectionhas eucalyptus from over 100 prove-nances, including the Eucalyptus nova-anglica. Eucalyptus tetrodonta and Eucalyp-

tus nova-anglica have very similar barkstructures. Both are rough barks wherethe outer layer dries out annually,causing the fibres to loosely intertwineand shed in short ribbons [Euclid: Euca-lypts of Australia, ‘Learn about Euca-lypts’, Centre for Plant BiodiversityResearch, http://www.anbg.gov.au/cpbr/cd-keys/euclid3/euclidsample/html/learn.htm (accessed 15 December2013), 29]. As bark glands are alsopresent in both, the biological structureof Eucalyptus tetrodonta and Eucalyptus

nova-anglica are highly comparable euca-lypts. Though the Eucalyptus nova-anglica

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be added to the pigments; however, due to the variability in the type andamount of binder used, as well as the possibility that some artists do notuse a binder, it was decided to remove this variable from the experiment.17

Omitting a binder would also have the added benefit of encouraging thepigments to be more friable, thereby ensuring that there would be a needfor consolidation while enabling the research to address the worst possibleconditions a bark painting may face. However, by doing so, the boards wereless likely to replicate flaking paint, another frequent condition concern forAboriginal Australian bark paintings and many ethnographic objects withmatte pigments. Flaking is a condition concern induced by the binder; asthe material dries, shrinks and ages, it can cause cleavage, cracking and yel-lowing of the paint in addition to the stresses caused by changes in the sub-strate. Thus, in order to have accounted for flaking paint, a binder wouldneed to have been selected and the boards then artificially aged, whichdid not fit within the time constraints of the research assessment. Therefore,it is important to note that partially bound pigments or those in an agingbinder would behave differently than those applied to the test boards.

The pigments were then applied to the bark as uniformly as possibleusing natural-bristle brushes, one for each pigment. Two phases of appli-cation were undertaken. The first involved application of one thick bandof each pigment to the board (the ‘base pigment’). The second involvedapplying one thin line of each pigment across the dry background pigmentsin one area of the board (the ‘upper pigment’). This approach was used toapproximate the presence of both flat pigments and hatched lines of pig-ments, as the two deteriorate differently (Fig. 1).

After drying, the pigments were examined to determine if artificial agingwould be necessary. However, significant loss of the white pigments wasalready noticeable as well as some areas of the yellow, red and black pig-ments. The level of deterioration was considered significant enough torequire consolidation. In order to increase the scope of the experiments,five of the boards were held horizontally and lightly shaken two to fourtimes to encourage the loss of more pigments. This meant that therewould be one board in fair condition and one board in poor condition

Fig. 1 Simulated test boards, before treatment with the consolidants.

bark sourced for the experiment camefrom England, the tree also grows inQueensland and New South Wales, Aus-tralia. Eucalyptus tetrodonta is native toWestern Australia, the Northern Terri-tory and Queensland [New SouthWhales Flora Online, ‘EucaLink: A WebGuide to the Eucalyptus’, PlantNET,http://plantnet.rbgsyd.nsw.gov.au/PlantNet/Euc/species.html (accessed 15December 2013)].

15 Tworek-Matuszkiewicz, ‘AustralianAboriginal Bark Paintings’, 18.

16 Luke Taylor, ‘Flesh, Bone, and Spirit:Western Arnhem Land Bark Painting’,in Art from the Land: Dialogues with the

Kluge-Ruhe Collection of Australian Abori-ginal Art, ed. H. Morphy and M.S. Boles(Charlottesville: The University of Virgi-nia, 1999), 49.

17 Boustead writes that in ArnhemLand, the pigments were often groundwith water only until creamy beforeapplication to bark. This provides valu-able information on bark painting pro-duction before 1966 and suggests thatsome earlier paintings might havebeen made without binder. Boustead,‘Conservation of Australian AboriginalBark Paintings’, 199.

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assigned to each of the four consolidants tested, and two boards withoutconsolidant left as control samples.

By using the test boards, the boards, pigments, preparation method, ageand environment all became controlled. Thus, both the inherent and exter-nal variables were greatly reduced so that the experiment could focus onthe treatment variables and their subsequent assessment.

The consolidants were selected for experimentation after extensive literaturereview, research and consultation with ethnographic conservators from variousinstitutions. Four consolidants were selected, each of which would be appliedto two test boards, leaving two untreated boards as controls (Table 1).

The primary reasons for selecting the consolidants included availability,resources and reported ease of use. As the ultimate goal was to design atreatment that could be replicated in numerous contexts, these allowancesfor practicality were important to the experiments’ success. Paraloid B72(ethyl methacrylate copolymer) is readily available in conservation labora-tories, affordable, has well-documented working and aging properties, andis highly soluble in a range of solvents and concentrations.18 However, it isnotable that there is an association of glossy surfaces with Paraloid B72.Additionally, for conservators working in warmer climates or with collec-tions that are occasionally exposed to higher temperatures, Paraloid B72’sglass transition temperature of 398C may be a deterrent. An alternativeacrylic resin such as Paraloid B67 may be preferred in these situations.

The second consolidant selected, Klucel G (hydroxypropyl cellulose), hasmany of the same benefits of Paraloid B72 including that it has a history ofapplication to organic materials. Unfortunately, a yellow cast has beenobserved on objects following its use and it has a much lower strength,even at higher concentrations, than other adhesives selected.19

Lascauxw Medium for Consolidation (MFC) (aqueous dispersion of anacrylic copolymer) was originally designed and marketed as a consolidant.However, little has been published on using MFC for the consolidation ofethnographic pigments. It is also a specialised product whose chemicalcomposition is not readily available.20 As an aqueous dispersion, it is poten-tially putting organic objects at risk due to the introduction of water.

Finally, while Lascaux JunFunoriw (water-soluble polysaccharide,extracted from the red algae genus Gloiopeltis furcata) is a more recentlyproduced consolidant, it is the purified form of Funori, which has a longhistory of use in Japanese paper conservation.21 While recent literature ishighly supportive of its use for consolidating paint, previous research hasnot focussed on ethnographic matte pigments. It is also very expensive,requires specific preparation, and has a limited shelf life. As with MFC,JunFunori is delivered as a water-based solution, which can impact onorganic material negatively.

Table 1 Initial visual impressions of treatment results for each consolidant. Grading: ++ verygood; + good; – neutral; 0 poor; 00 unsuitable. Pigment colours: R red; Y yellow.

Paraloid B72 Klucel G

Lascaux Medium

for Consolidation

(MFC) JunFunori

No residue ++ ++ ++ 0No gloss ++ ++ ++ 0No colour change 2 2 2 0

RY saturated R saturated RY saturated R saturatedNo darkening 2 2 2 0

RY saturated R saturated RY saturated R saturatedBase pigment adhesion ++ + + ++Upper pigment adhesion 0 0 0 ++Necessity of

post-treatment cleaningNo Yes, mild Yes, mild Yes, mild

18 Material Safety Data Sheets (MSDS);Sylvia Rodgers, ed., ‘Consolidation/Fixing/Facing’, American Institute ofConservation Paper Group Catalogue

(1988), http://cool.conservation-us.org/coolaic/sg/bpg/pcc/23_consolidating-fixing-facing.pdf (accessed 20 April2013), 10–1; Chantal-Helen Thuer, ‘Scot-tish Renaissance Interiors: Facing andAdhesives for Size-Tempera PaintedWood’, Historic Scotland Technical Paper11 (2011): 40.

19 MSDS; Thuer ‘Scottish RenaissanceInteriors’, 38–9.

20 MSDS; Hedlund and Johansson, ‘Pro-totypes of Lascaux’s Medium for Conso-lidation: Development of a NewCustom-Made Polymer Dispersion forUse in Conservation’, Restauro 6 (2005):432–39. Thuer ‘Scottish RenaissanceInteriors’, 43.

21 MSDS; Thomas Geiger and FrancoiseMichel, ‘Studies on the PolysaccharideJunFunori Used to Consolidate MattePaint’, Studies in Conservation 50, no. 3(2005): 193–204; Hayakawa, N.,

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The other consolidant originally considered for testing was Aquazolw

(polyoxazoline).22 However, JunFunori was selected over Aquazolw asrecently published case studies using JunFunori demonstrated greaterpotential for application to indigenous matte pigments.23

2 Solvent and consolidant considerationsAfter selecting the four consolidants, it was necessary to determine the bestsolvent and concentration for consolidating matte pigments.24 A prelimi-nary experiment was undertaken to discover the best consolidant concen-tration by applying ground red ochre without a binder to a number ofplaster of Paris cubes. Because of the surface of the plaster, the pigmentwas able to key-in, forming a smooth layer that was not disturbed byblowing. A range of concentrations of the four consolidants in varyingsolvents were then applied and the results visually and mechanically ana-lysed.25 The visual assessment looked for signs of darkening and glossi-ness, whereas the mechanical assessment involved rubbing a clean,gloved finger across the surface to determine whether any pigment wasremoved. The experiment used plaster rather than bark in order to preservethe limited amount of eucalyptus available for the main experiment.Although it is a different substrate, it was still felt that the preliminaryexperiment was a good way to test consolidant concentrations.

Paraloid B72 was tested in acetone at 0.5%, 1% and 1.5% w/v concen-trations; in a 50:50 (v/v) acetone: Industrial Methylated Spirit (IMS) mixat 0.5%, 1% and 1.5% concentrations; and in xylene at 0.5%, 1% and 1.5%.A 1.5% w/v solution in xylene was chosen as the best approach. Xylenewas found to provide the best saturation and least disruption of the pig-ments. At 1.5% concentration, no pigment was disturbed when tested,whereas at lower concentrations, a gloved finger could remove the redochre pigment.

Although Klucel G can be dissolved in water, it was decided that IMSwould be a better solvent so as to avoid introducing large volumes ofwater into the bark substrate during the main experiments. Therefore,0.25%, 0.5% and 0.75% solutions of Klucel G in IMS were tested on theplaster cubes. At 0.75%, no pigment was disturbed when tested,whereas pigment could be removed at concentrations below 0.75%. There-fore a solution of 0.75% w/v Klucel G in IMS was chosen for this conso-lidant.

Lascaux MFC is purchased as a solution, and therefore was tested at fullstrength, and diluted with deionised water to 0.5%, 1%, 2%, 5%, 10% and20% v/v solutions. A 5% MFC v/v in water was originally determined tobe too dark and glossy to be a satisfactory concentration. However, thelower concentrations did not effectively adhere the pigment, and colourchange and gloss remained issues. Therefore 5% MFC v/v in deionisedwater was selected as a compromise because it was the minimum concen-tration tested that successfully adhered the pigments to the plaster.

JunFunori was tested only at the specification recommended by the man-ufacturer, which is 1% in deionised water.

3 Test board experimentAfter deciding on the solvent and concentrations of each consolidant, theseconsolidants then needed to be applied to the test boards and the resultscompared to determine which material and method was most effective.Thus, choosing the method of application was the next major experimentaldecision. Arguably, the method of application is as significant to the resultsas is the consolidant used.26 Using the same method of application for eachconsolidant would benefit the experimental design by reducing the numberof variables. However, it would also put some of the materials at a disad-

Kigawa, R., Nishimoto, T., Sakamoto, K.,Fukuda, S., Kirnishima, T., Oka, Y., andKawanobe, W., ‘The Characterizationof Furunori (Aged Paste) and Prep-aration of a Polysaccharide Similar toFurunori’, Studies in Conservation 52(2007): 221–32; Alice Tate-Harte,Chantal-Helen Thuer, and MaureenCross, ‘Funori: A New Medium for Con-solidation and Retouching’, The PictureRestorer 36 (2010): 13–14; FrancoiseMichel, ‘Funori and JunFunori: TwoRelated Consolidants with SurprisingProperties’ (paper presented at Sym-posium 2011: Adhesives and Consoli-dants for Conservation: Research andApplications, Canadian ConservationInstitute, 2011), 1–14; Thuer, ‘ScottishRenaissance Interiors’, 35–6; ErikaSandbakken and Eva Tveit, ‘EdvardMunch’s Monumental Sketches (1909–1916) for the Aula of Oslo University,Norway: Conservation Issues and Treat-ments’, Studies in Conservation 57 (2012):258–67.

22 Julie Arslanoglu, ‘Aquazol as Used inConservation Practice’, WAAC Newslet-

ter 26, no. 1 (2004): 10–5.

23 Sandra Grantham, ‘Byobu andFusuma: Developing an Approach tothe Conservation of Japanese Screensthrough Technical Study and anInvestigation of Current Practices’(unpublished PhD thesis, RoyalCollege of Art/Victoria and AlbertMuseum Conservation Programme,1998); Geiger and Michel, ‘Studies onthe Polysaccharide JunFunori’, 193–204; Michel, ‘Funori and JunFunori’,1–14; Rosario Pacheco and Abrahamde la Torre, ‘The Combined Use ofthe Ultrasonic Atomizer with Low-Pressure Micro Table in the Consoli-dation of Contemporary Paintings’(poster presented at Symposium2011: Adhesives and Consolidantsfor Conservation: Research andApplications, Canadian ConservationInstitute, 2011), http://www.cci-icc.gc.ca/symposium/2011/Poster%20-%20Llamas%20Pacheco%20and%20Torre%20-%20English.pdf (accessed 1March 2013); Sandbakken and Tveit,‘Edvard Munch’s MonumentalSketches’.

24 Chris Stavroudis and Sharon Blank,‘Solvents and Sensibility’, WAAC News-

letter 11, no. 2 (1989): 2–10.

25 The experiments were conducted inaccordance with relevant COSHH regu-lations and using Material Safety DataSheets (MSDS). Health and SafetyExecutive, The Control of Substances

Hazardous to Health Regulations 2002.Approved Code of Practice and Guidance,

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vantage. A literature review was undertaken to determine what methodswere currently being used with each material.27 As a result of the literaturereview, application via ultrasonic mister or nebuliser was considered.However, the lack of published research dedicated to this topic, conflictingresults, lack of access to the equipment, and the equipment’s restrictions interms of solvents all contributed to the decision not to test spray or mistapplication at this time. Instead, it was decided that all would be appliedusing a large sable hair brush, selected to reduce the strokes necessaryand to spread any pressure applied. However, based on the recommen-dations of Michel, application of the 1% Lascaux JunFunori in deionisedwater was via a large sable hair brush applied over a layer of Japanesetissue facing.28 Afterwards, a piece of silicon release paper and a glassweight were placed on top until the consolidant was dry.

Before and after application of consolidants, the four test groups were keptin closed chambers. The Paraloid B72 and Klucel G boards were placed insolvent chambers by adding approximately 15 ml of their respective solventsin beakers containing cotton wool. This was designed to improve consolidantpenetration and prevent darkening and tide lines. Because the pigmentswere not highly soluble in xylene or IMS, the risk to them of using asolvent atmosphere was relatively low. However, there may be caseswhere the risk associated with solvent atmospheres would be too high.29

The closed chambers for the water-based consolidants did not have anysolvent inside them but served as a means to reduce environmental fluctu-ations during the experiment, and limited the rate of evaporation of the con-solidant solution. While this approach was useful for the purpose of theexperiments, it would be very difficult to use solvent chambers when treat-ing a large object or bark painting. Instead, one of the techniques used inmatte pigment consolidation that serves a similar purpose is pre-wettingthe area to be treated with a complementary solvent.30

The final step prior to treatment was assigning boards to each consoli-dant. A blind procedure was used within the two groups, those in fairand those in poor condition, in order to avoid preferential selection. Anunbiased observer numbered each test board and a second observerassigned the numbers to categories. Two boards were assigned to each ofthe five categories: control, Paraloid B72, Klucel G, MFC and JunFunori.

At the time of consolidant application, environmental conditions in the lab-oratory were 188C and 55%RH. Though it had been a concern that the brushwould lift pigment, this was found to be only a minor issue; very smallamounts of red ochre were removed from several boards. The applicationof the JunFunori occurred without incident despite the author’s initial con-cerns regarding the efficacy of a facing treatment on powdered paint surfaces.

Three days after consolidation, the boards were checked and determinedto be fully dry. The solvent chambers were left open with a piece of Bondina(non-woven polyester) 30gsm sheet protecting the boards from any dust orfibres settling on the surfaces. A week after application, each board wasanalysed to determine the success of the treatments.

4 Analytical methodologyAssessing the results of the experiments on the test boards demanded aprimarily qualitative approach, as no quantifiable method of determiningthe degree of success of each treatment could be identified as both effectiveand achievable within the time and resource constraints of the project.

The visual appearance of the pigments on the boards was assessed first(Fig. 2). A Minolta spectrophotometer was used before treatment to deter-mine an average colour reading with the goal of repeating the procedureafter treatment and developing a mean colour change as a result of the appli-cation of each of the consolidants. However, the initial readings of each

2013, sixth edition, http://www.hse.gov.uk/pubns/priced/l5.pdf (accessed20 May 2014).

26 Eric Hansen and Rosa Lowinger,‘Investigations into Techniques for theConsolidation of High PigmentVolume Concentration Paint at theGetty Conservation Institute’, WAACNewsletter 12, no. 3 (1990): 13–4.

27 Elizabeth Welsh, ‘A ConsolidationTreatment for Powdery Matte Paint’, inPreprints of Papers Presented at the EighthAnnual Meeting of the American Institutefor Conservation of Historic and Artistic

Works (San Francisco: AIC, 1981), 141–50; Rodgers, ‘Consolidation/Fixing/Facing’; Hansen and Lowinger, ‘Investi-gations into Techniques for the Consoli-dation of High Pigment VolumeConcentration Paint’; Christine Daintith,‘A Consolidation Treatment for Ethno-graphic Pottery from New Guinea’, inWhere to Start, Where to Stop? Papers fromthe British Museum/MEG Ethnographic

Conservation Colloquium: In Memory ofHarold Gowers (Hull: Museum Ethnogra-phers’ Group, 1995), 121–30; Grantham,‘Byobu and Fusuma’; Stefan Michalski,Carole Dignard, Lori van Handel andDavid Arnold, ‘The Ultrasonic Mister:Applications in the Consolidation ofPowdery Matte Paint on Wooden Arti-facts’, in Painted Wood: Conservation andHistory, ed. V. Dorge and F.C. Howlett(Los Angeles: Getty Conservation Insti-tute, 1998), 498–513; Hedlund andJohansson, ‘Prototypes of Lascaux’sMedium for Consolidation’; LuciaBurgio, Shayne Rivers, CatherineHiggitt, Marika Spring and MingWilson, ‘Spherical Copper Resinate onCoromandel Objects: Analysis and Con-servation of Matt Green Paint’, Studies inConservation 52 (2007): 241–54; Tworek-Matuszkiewicz, ‘Australian AboriginalBark Paintings’; Wendy Baker andDavid Grattan, ‘Dimensional Changesof Wood Immersed in Different Consoli-dant Agents’, Adhesives and Consolidantsfor Conservation: Research and Applications:

Proceedings (2011): 1–15; Michel, ‘Funoriand JunFunori’; Pacheco and de la Torre,‘The Combined Use of the Ultrasonic Ato-mizer’; Thuer, ‘Scottish RenaissanceInteriors’; Sandbakken and Tveit,‘Edvard Munch’s Monumental Sketches’.

28 Michel, ‘Funori and JunFunori’, 1–14.

29 Eric Hansen, Sue Walston and Mitch-ell Bishop, ‘Matte Paint: Its History andTechnology, Analysis, Properties andConservation Treatment: With a SpecialEmphasis on Ethnographic Objects’,WAAC Newsletter 18, no. 2 (1996): 1–10.

30 Hansen, Walston and Bishop, ‘MattePaint’, 9.

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pigment band before treatment showed that the spectrophotometer read-ings were imprecise in the order of 6000% within a single pigment. It wasfelt that the results of this form of analysis were not reliable and the readingswere not repeated after treatment. Thus, colour change was assessed by eyeand photographic comparison. Next, a range of abrasion tests was per-formed and the effects of the different forms of abrasion visually assessed.The visual assessments were recorded on charts (Tables 1 and 2).

The test boards were initially assessed for whether a consolidant residueremained on the surface, whether the surface was glossy, whether it had dar-kened, how well the base pigment layer was still adhered to the surface andhow well the upper pigment layer was still adhered to the surface (Table 1). Ifany areas of consolidant pooling or displaced pigment were observed, it wasnoted that the test board would have required post-treatment cleaning,though this was not actually carried out. The results of the analyses weregraded for each pigment (B for black, R for red, W for white and Y foryellow) and using a five-point scale from very good (++) to unsuitable (00).

The abrasion tests were performed once on each board by three differentconservators, for a total of three abrasion tests on each board.31 Each assess-ment was completed in the same time period to ensure as much consistencyas possible, as involving multiple people or taking breaks can contribute tovariations in condition assessments. The scale used was the same as for thevisual assessments. A simple condition check methodology is the bestway to avoid statistical errors.32

Different types of abrasion were applied to each pigment area on eachboard. The abrasion was applied so as to gradually increase pressureand/or intensity, to provide a scale of abrasiveness. The types of abrasionapplied to each pigment area of each board were: nitrile glove, gentle

Fig. 2 Simulated test boards, after treatment. Boards 1 and 7 had no consolidation (controlsamples); 2 and 6 were consolidated with JunFunori; 3 and 8 were consolidated with LascauxMFC; 4 and 9 were consolidated with Paraloid B72; 5 and 10 were consolidated with Klucel G.

31 Data presented in Table 2 record theresults of one set of abrasion tests. Theresults from the two other testers didnot significantly differ from these, eventhough each assessment occurred in iso-lation.

32 Joel Taylor and Siobhan Stevenson,‘Investigating Subjectivity within Col-lection Condition Surveys’, MuseumManagement and Curatorship 18, no. 1(1999): 19–42.

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rub; nitrile glove, firm rub; bare finger, gentle; bare finger, firm; pat withacid-free tissue, simulating wrapping; gentle roll with smoke sponge;sable hair brush, dry; cotton swab, dry; cotton swab, damp with deio-nised water; gentle blow, horizontal; gentle shake, vertical. Once aboard was deemed unsuitable (00), the abrasion test was stopped(Table 2). These actions were meant to increase in applied pressure andrisk to the pigments while simulating actions that may actively or pas-sively occur to bark paintings in museum or collection contexts.Though only semi-quantifiable, Geiger and Michel also advocate forthe use of a ‘finger’ or pressure-sensitive test similar to the one employedhere; the scale used to measure the abrasion tests was based on the workof Thuer.33

Results1 Visual assessmentIn summary, the test boards treated with 1.5% w/v Paraloid B72 in xylenehad well-adhered upper layers of pigments, and the base pigments weredifficult to abrade and did not show chromatic change. These were theonly boards that would not have required any surface cleaning after treat-ment in order to reduce discrete areas of gloss. The 0.75% w/v Klucel G inIMS treated boards showed some staining. While some areas of the upperlayers of pigments were well adhered, the yellow, red and black pigmentswere still friable in both the upper and base pigments. The 5% v/v LascauxMFC in deionised water treated boards produced results highly similarto the Klucel G treatments. The surface remained matte, though therewere areas of staining in the red and yellow base layers. The upper andbase layer pigments remained friable and possible to abrade by touch.The final test group, the 1% w/v Lascaux JunFunori in deionised watertreated boards, demonstrated strong adhesion of both the upper and basepigments. The JunFunori boards were the only ones that could be shakenand blown without loss. However, some of the flakes were adhered outof alignment and would be difficult to relocate; there was also a small

Table 2 Results of the author’s abrasion tests, performed on each simulated test board after treatment. Grading: ++ very good; + good; –neutral; 0 poor; 00 unsuitable. Pigment colours: B black; R red; W white; Y yellow.

1.5% w/v Paraloid

B72 in xylene

0.75% w/v Klucel G

in IMS

5% v/v MFC in

deionised water

1% w/v JunFunori

in deionised water

Control—no

treatment

Bark sample boards 4 9 5 10 3 8 2 6 1 7Nitrile glove, gentle + Y + Y 2 Y 2 Y + BRY + BRY ++ ++ 00 00

2 BRW 2 BRW 0 BRW 0 BRW 0 W 0 W BRWY BRWY BRWY BRWYNitrile glove, firm 2 WY 2 Y 2 BY 2 BY 2 BY 2 BY + WY + WY

0 BR 0 BRW 0 RW 0 RW 0 RW 0 RW 2 BR 2 BRBare finger, gentle + Y + Y 2 Y 2 Y 2 BY 2 BY + WY + WY

2 BRW 2 BRW 0 BRW 0 BRW 00 RW 00 RW 2 BR 2 BRBare finger, firm 2 WY 2 Y 2 BY 2 BY 2 BY 2 BY + WY + WY

0 BR 0 BRW 0 RW 0 RW 00 RW 00 RW 2 BR 2 BRAcid free tissue 2 Y 2 Y + BWY + BWY + WY + WY

2 BRWY 2 BRWY 0 BRW 0 BRW 0 R 0 R 2 BR 2 BRSmoke sponge 2 Y 2 Y 2 Y 2 Y 2 BY 2 BY + WY + WY

0 BRW 0 BRW 00 BRW 00 BRW 00 RW 00 RW 2 BR 2 BRSable hair brush, dry 00 00 00 00 2 B 2 B + BRWY + BRWY

BRWY BRWY BRWY BRWY 00 RWY 00 RWYCotton swab, dry 2 B 2 B + BRWY + BRWY

00 RWY 00 RWYCotton swab, wet 00 BRWY 00 BRWY + BW + BW

0 RY 0 RYGentle blow, horizontal + BRWY + BRWYGentle shake, vertical + BRWY + BRWY

33 Geiger and Michel, ‘Studies on thePolysaccharide JunFunori’, 193–204;Thuer, ‘Scottish Renaissance Interiors’.

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area of high gloss on the black pigment bands, which may be a result of anirregularity in application.

Pigment displacement was further analysed by comparing the before andafter treatment images, which were taken in identical lighting conditionsand with identical camera settings, for consistency. As seen in Figure 1and Figure 2, the MFC boards (3 and 8) show pigment displacement to adegree not noted on any of the other test boards. This is particularly truefor the upper layer of white pigment on board 8.

Generally after each treatment, the white pigment was the most friable,and the red and yellow pigments often appeared more saturated incolour when compared to the control boards. The staining that occurredwith the Klucel G and MFC treatments could be due to anomalies in thebark. Only the JunFunori treatment caused minor issues with glossiness,though they were localised and could be reduced by gentle surfacecleaning.

Prior to consolidation, the boards were examined and documented inultraviolet light. The white pigment was highly fluorescent; however,little else was noted. After treatment, the process was repeated with theexpectation that there would be increased fluorescence due to the additionof consolidants, similar to how adhesives fluoresce. However, the onlyfluorescence present was due to the white pigment, as before.

2 Abrasion testsThe analyses revealed that the abrasion results did vary slightly by pigmentbut not greatly between the two boards of varying condition. The Kluceland Paraloid boards both reached an unsuitable grade of abrasion at‘sable hair brush, dry’. The MFC boards also reached the unsuitablegrade at ‘sable hair brush, dry’ except for the black pigment, whichbecame unsuitable at ‘cotton swab, wet’. The JunFunori board maintaineda good rating through all the abrasion tests.

However, the abrasion test demonstrated in Table 2 did not take thedifference in behaviour of the base and upper pigments into account.After testing, visual evaluation indicated that there was a difference in be-haviour between the two areas for all of the consolidants except JunFunori,which performed equally well for both pigment types (Table 2).

Discussion of resultsThe research aim of gaining a better understanding of consolidants andapplication methods was achieved. The process of applying selected con-solidants to test boards with properties similar to Aboriginal Australianbark paintings to identify, of the consolidants tested, which were mostsuited to treating friable matte pigments identified two effective materials.Importantly, the experiment confirmed the applicability of a relatively newand under-published material, JunFunori, while also supporting the use ofParaloid B72. Though the black pigment on the MFC boards outperformedParaloid B72 in abrasion tests, the pigment displacement caused by MFCwas considered unacceptable. Additionally, Table 2 demonstrates thatParaloid B72 and JunFunori provided better base-pigment adhesion. Thebase pigment layers are those more representative of friable pigment.The upper pigment layers were applied as a thicker paste and presentedissues more analogous to flaking paint. Thus, in this experimentalcomparison, Paraloid B72 and JunFunori were the most effective consoli-dants for friable matte paint on bark.

The research was also able to generate significant areas that requirefurther investigation in order to continue seeking the best practice approachto treating friable matte pigments. In terms of materials, future work shouldconsider the inclusion of Aquazolw, methyl cellulose, starch pastes, pro-

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teinaceous glues and adhesive combinations as consolidants.34 These havebeen recommended and used by conservators for consolidating matte pig-ments; similarly, a thorough survey of current practice amongst conserva-tors treating matte pigments on organic substrates could supply furthermaterials and methodologies. It is also possible to introduce a mattingagent such as fumed silica into the consolidant to reduce glossiness,though the implications (ethical and material) should be strongly con-sidered before this is undertaken.35 Finally, the discussion around usingsynthetic or natural material is ever-present in the conservation literature.The impact of using one over the other in the context of fully organicworks could be more extensively addressed; alternatively, it can remain adecision left to the individual practitioner and their context. Where poss-ible, conservators can include the original artists, owners and culturalrepresentatives of the art in conversations regarding treatment method-ology. Research into the identification of binders and how the binderaffects treatment could also be pursued. Traditional and synthetic bindersremain a huge variable in the preparation and subsequent treatment ofbark paintings. Understanding their effect on condition would be veryinformative.

Application methodology offers even more possibilities than materials,many of which have been attempted with a range of resulting effectiveness,as demonstrated by the relevant publications. The issue of pigment displa-cement seen on the MFC boards may be a result of application methodologymore so than an issue implicit in the material. As such, a comprehensivecomparative study of the efficacy and risks inherent in the various appli-cation methods would be very beneficial to the field. Focus could beapplied to the use of an atomised sprayer, vacuum-forced consolidationand application through a facing layer as was used for the JunFunori.36

There are also restrictions on application methodology depending on thematerial. For example, Thuer explains that the British Museum sometimesuses ultrasonic humidifiers for the application of water-based consolidantsand brushes for low percentages of solvent-based consolidants.37 However,MFC is said to be weakened by atomisation and JunFunori is a macromol-ecule, which can hinder spraying even at the low concentrations rec-ommended. Thus, the subject remains complex.

The theory and technique of consolidating pigment on bark paintingsalso shows room for expansion. One of the possibilities would be the div-ision of research into the best approach to consolidating base pigmentversus upper (hatched) pigments, as smaller concentrations of consolidantcould be suitable for some scenarios, or alternative application methods.Two different, but complementary approaches could also be employed,such as a general application of a low concentration consolidant for base-pigment adhesion and a localised application of a higher concentration con-solidant via immiscible solvents for upper pigment layers.38 A thick Japa-nese tissue facing layer may be suitable for repairing tenting and flakingthree-dimensional pigments.39

A second iteration of this experiment but using concentrations 50–75%lower with multiple applications would also be interesting. Potentially, acombination of this approach and the introduction of application via afacing layer for all of the consolidants could provide a low-risk, high-reward consolidation scenario. If a low concentration were applied bysable brush, allowed to dry, and then applied again via the facing andweights method, potentially little pigment would be lost and adhesion ofthe pigments to the substrate would be greater.

Developing an effective and cost-efficient method of quantifying conso-lidation and depth-penetration would advance this research’s ability toaffect treatment processes. Research has been undertaken to determine

34 Arslanoglu, ‘Aquazol as Used inConservation Practice’; Tworek-Matusz-kiewicz, ‘Australian Aboriginal BarkPaintings’; Bettina Ebert, Brian Singerand Nicky Grimaldi, ‘Aquazol as a Con-solidant for Matte Paint on VietnamesePaintings’, Journal of the Institute of Con-

servation 35 (2012): 62–76; DominiqueCocuzza, email message to author, 17February 2013.

35 Burgio et al., ‘Spherical Copper Resi-nate’.

36 Welsh, ‘A Consolidation Treatmentfor Powdery Matte Paint’; Daintith, ‘AConsolidation Treatment for Ethno-graphic Pottery from New Guinea’,121–30; Grantham, ‘Byobu andFusuma’; Michalski et al., ‘The Ultra-sonic Mister’, 498–513; Burgio et al.,‘Spherical Copper Resinate’; Tworek-Matuszkiewicz, ‘Australian AboriginalBark Paintings’; Michel, ‘Funori andJunFunori’; Pacheco and de la Torre,‘The Combined Use of the UltrasonicAtomizer’; Thuer, ‘Scottish RenaissanceInteriors’, 25; Sandbakken and Tveit,‘Edvard Munch’s MonumentalSketches’.

37 Thuer, ‘Scottish RenaissanceInteriors’, 25.

38 Burgio et al., ‘Spherical Copper Resi-nate’, 241–54.

39 Thuer, ‘Scottish RenaissanceInteriors’, 18–20.

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the depth of penetration using technology such as Optical Coherence Tom-ography (OCT), however the results of this method still require qualifica-tion before it could be used more widely by conservators.40

As in all conservation treatments, fundamental theories and debates con-tinue to require consideration and careful response. Of foremost importanceis the objective of the treatment. In order to determine which treatment ismost suitable, there must be a consensus as to what the end goal of the treat-ment should be. For the stakeholders, what counts as ‘good’ condition?Similarly, what are the most important aspects of the bark paintings? Is itthe colour, the design or the survival of the piece for as long as possible?Could there be a sliding scale for treatments, which allows conservatorsto select their areas of flexibility and inflexibility in terms of the ultimateresult? These questions cannot be answered on a broad scale and insteadmust be widely discussed for each context and set of objects. Publicationsof specific case studies demonstrating the decision-making processesused and the stakeholders consulted would increase transparency andimprove the ability of other conservators to pursue similar processes.

Whilst the research was designed to reflect the materials and conditionconcerns of Aboriginal Australian bark paintings, it did not replicate theconservation methodology for real objects for many reasons. Firstly, it isunlikely that an entire bark painting would ever be treated in the waythe test boards were. Much more common is the localised treatment oflifting paint.41 In these cases, techniques suitable to flake laying are morerelevant than those of friable paint. Additionally, according to Thuer’sresearch, MFC and Aquazol are much more useful in this situation thanthey are in consolidating friable pigment.42 Thus, were this research rede-signed to focus on flaking paint, it is possible that the same consolidantsthat underperformed here would actually be better suited. Additionally,the above experiments do not reflect on the possibility of previous treat-ments. If bark paintings have already been treated for friable and flakingpaint, whether within a museum context or at the time of acquisition,any treatment will have to consider the non-original materials present.

What was successfully achieved through the experiments describedabove was an analysis of four common consolidant families (acrylic, cellu-lose ether, acrylic dispersion and polysaccharide glue). Two of the consoli-dants tested, Paraloid B72 and Klucel G, represent common conservation-grade materials generally available. The other two, MFC and JunFunori,are commercial products specifically marketed for pigment conservation.That both Paraloid B72, a synthetic, and JunFunori, a purified version ofa natural adhesive, can be recommended with qualifications is also abenefit to the study of consolidants, because the experiments show evi-dence for the success of two theoretically divergent approaches.

ConclusionsThe comparative study of consolidation treatments for Aboriginal Austra-lian bark painting indicates that there is significant room for furtherresearch, both in refining the experimental methodology and throughstudying additional variables. For the author, the examination of multipleapplications of low concentrations of consolidants as well as the impactof application methodology are the most pressing areas for future research.However, the development of an accepted and replicable assessment tech-nique will be essential to the acceptance of experimental results.

Originally, the goal of the experiments was that the test boards, as repre-sentatives of Aboriginal Australian bark paintings, would be in a conditionin which they could be displayed, stored, studied and transported withoutserious damage to the paint layers. All four consolidants accomplished thisas adhesion of the pigment to the bark substrate was significantly improved

40 Karolina Soppa, Tilly Laaser andChristoph Krekel, ‘Visualizing the Pen-etration of Adhesives Using FluorescentLabelling’ (paper presented at Sym-posium 2011: Adhesives and Consoli-dants for Conservation: Research andApplications, Canadian ConservationInstitute, 2011), 1–18; Joyce Zucker,Mary Betlejeski and Erin Moroney,‘Nanotechnology and Materials Testing:Using Nanoparticles to Tag Consolidantsto Determine Depth of Penetration’,National Center for Preservation Tech-nology and Training, 2011, http://ncptt.nps.gov/wp-content/uploads/2011-051.pdf (accessed 10 March 2013).

41 Beata Tworek-Matuszkiewicz, emailmessage to author, 11 June 2013.

42 Thuer, ‘Scottish RenaissanceInteriors’, 25.

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on all eight boards after treatment. Furthermore, the primary concern ofconsolidation altering the visual appearance of the paintings, namely thematte nature of the pigments and their intended chromas, was shown tobe largely irrelevant for the four concentrations tested. Thus, the aim ofidentifying consolidants and concentrations that could be applied to thebark paintings to prevent further loss and deterioration while not affectingthe aesthetics and significance of the pigments and designs was achieved.Lascaux JunFunori can be recommended for highly friable pigments, par-ticularly for paint flake relaying (for example lifting hatching). It could beapplied at 0.5% concentration and reapplied as necessary, as suggestedby Michel.43 Paraloid B72 can also be recommended for areas of lesssevere paint powdering. At a higher concentration or with multiple appli-cations, Paraloid B72 could also be an effective consolidant for flaking paint.

That this experiment could positively recommend both a synthetic and anatural consolidant was an unexpected but encouraging result that allowsfor a customisable approach to treating Aboriginal Australian bark paint-ings, in that individual collections and conservators can make decisionsappropriate to their own principles and contexts without sacrificingquality of treatment. Further development of the topic could show that,in the context of consolidating friable, matte pigments, professional ethicsand resource availability can safely be afforded priority due to thesuccess of diverse consolidation treatments.

Acknowledgements

The author would like to thank Dr Margo Smith, Director of theKluge-Ruhe Aboriginal Art Museum, University of Virginia, USA,and Dominique Cocuzza, former Assistant Curator. In my time atthe Kluge-Ruhe as an intern, and throughout the course of thisresearch, both Margo and Dominique were extremely supportive,always available and instructive. Their willingness to share theirown expertise and to encourage the development of my own wasessential to the development and execution of this research topic.

I am also extremely grateful to Tom Hart Dyke, creator of Lulling-stone Castle’s World Garden, for personally delivering the Eucalyp-

tus nova-anglica bark for the replica boards. His willingness to help,depth of botanical knowledge and interest in the project were funda-mental to making the experimental component possible.

Finally, the MSc in Conservation for Archaeology and Museumslecturers and supervisors were exceedingly influential, from theproject’s initial conception to analysing the outcome. RenataPeters, Dean Sully and James Hales greatly assisted me in designingthe experiment, always ensuring that I was asking the right ques-tions and pursuing useful answers. I am also grateful to the conser-vation programme for providing the resources necessary to executethe experiment.

Abstract

Flaking and friable paint has long been noted as a condition concernof collected ethnographic art and material culture. Over the years,various materials for the consolidation of friable matte pigmentshave been recommended, from resins to commercial fixatives andvarnishes. This article continues the investigation of appropriateconsolidants for friable earth pigments specifically from theperspective of Aboriginal Australian bark paintings. Due to theimportance of colour and design in communicating significanceand provenance in bark paintings, conservation treatments mustavoid altering these properties. With this in mind, the experimentdescribed herein compared the efficacy of four consolidants in treat-ing highly friable pigments on simulated test boards. Of the fourmaterials—Paraloidw B72, Klucelw G, Lascauxw Medium for Con-solidation and Lascaux JunFunoriw—JunFunori and Paraloid B72were the most effective at improving cohesion and adhesion of the

pigments. However, further work is necessary before a treatmentprocess can be determined. This paper identifies areas requiringfuture research including comparisons of application methods andthe introduction of varying concentrations and multiple appli-cations of the four consolidants tested.

Resume

«Traitement des pigments mats et friables sur ecorce: analyse experi-mentale de quatre consolidants»L’ecaillage et la friabilite de la peinture ont longtemps ete considerescomme preoccupants pour l’art ethnographique et les materiauxculturels collectes. Au fil des annees, divers materiaux pour la con-solidation des pigments mats et friables ont ete recommandes, allantdes resines jusqu’aux fixatifs et vernis commerciaux. Cet articleapprofondit la recherche sur les consolidants appropries pour lespigments mineraux friables, en particulier sur les ecorces peintesdes autochtones australiens. L’importance de la couleur et dudessin pour connaitre la signification et la provenance des ecorcespeintes est telle que les traitements de conservation doivent eviterde modifier ces proprietes. Dans cet esprit, l’experience decrite icia compare l’efficacite de quatre consolidants pour le traitementdes pigments tres friables sur des panneaux de simulation. Parmiles quatre materiaux (Paraloidw B72, Klucelw G, Medium de conso-lidation Lascauxw et JunFunori Lascauxw) le JunFunori et le Para-loid B72 etaient les plus efficaces pour ameliorer la cohesion etl’adherence des pigments. Toutefois, d’autres travaux sont neces-saires avant qu’un protocole de traitement puisse etre determine.Cet article identifie les champs necessitant des recherches ulter-ieures, en particulier les comparaisons des methodes d’application,l’introduction de differentes concentrations et des applications repe-tees des quatre consolidants testes.

Zusammenfassung

„Die Behandlung brockeliger matter Pigmente auf Baumrinde: eineexperimentelle Analyse vierer Konsolidierungsmittel“Blatternde und fragile Farbschichten sind seit langem als problema-tischer Zustand von ethnographischen Nutz- und Kunstgegenstan-den bekannt. Uber die Jahre wurden viele Materialien von Harzen

43 Michel, ‘Funori and JunFunori’.

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bis zu kommerziellen Fixativen und Firnissen fur die Sicherung vonmatten Malschichten empfohlen. Dieser Artikel fuhrt die Untersu-chung geeigneter Sicherungsmittel aus der Perspektive australischerAboriginal Borkenmalerei weiter. Aufgrund der Wichtigkeit vonFarbe und Design in der Kommunikation von Signifikanz und Pro-venanz mussen Konservierungsmaßnahmen unbedingt vermeidendiese Eigenschaften zu verandern. Vor diesem Hintergrundwurden in dem nachfolgend beschriebenen Experiment die Effekti-vitat von vier Sicherungsmitteln fragile Farbschichten auf einer Test-tafel zu sichern miteinander verglichen. Von den vier Mitteln—Paraloidw B72, Klucelw G, Lascauxw Medium fur Konsolidierungund Lascaux JunFunoriw—waren Lascaux JunFunori und ParaloidB72 am effektivsten was die Wiederherstellung von Zusammenhaltund Adhasion der Farbe angeht. Allerdings ist weitere Arbeit notig,bevor ein Behandlungsprozess erstellt werden kann. Dieser Artikelidentifiziert Bereiche, die in der Zukunft weiter erforscht werdenmussen; unter anderem ist dies die Art der Anwendung der Sicher-ungsmittel, Variationen in der Konzentration und multiple Applika-tionen der vier Sicherungsmittel.

Resumen

“Tratamientos de pigmentos mates friables en corteza: Analisisexperimental de cuatro consolidantes”En las colecciones de arte etnografico y cultura material, desde hacetiempo se viene senalando la preocupacion por el estado de las pin-turas friables y descascarilladazas. A lo largo de los anos, se han idorecomendando una variedad de materiales de consolidacion paralos pigmentos mates friables, desde resinas hasta fijadores comer-

ciales y barnices. En este artıculo, se continua la investigacion paraencontrar un consolidante adecuado para el tratamiento de los pig-mentos de tierra friables, especialmente para los de las pinturasaborıgenes australianas sobre corteza. Debido a la importancia demantener el color y el diseno para poder comprender el sentido yla procedencia de estas pinturas en corteza, es necesario que los tra-tamientos de conservacion no los modifiquen. Por ello, los experi-mentos descritos aquı comparan la eficacia de cuatroconsolidantes en el tratamiento de pigmentos altamente friablesusando tablas simuladas en las pruebas. De los cuatro materialesexaminados—Paraloidw-B72, Klucelw G, Medio de consolidacionLaxcauxw y JunFunoriw Lascaux—los mas efectivos a la hora demejorar la cohesion y adhesion de los pigmentos fueron JunFunoriy Paralois B72. Sin embargo, antes de poder determinar unproceso de tratamiento, es necesario llevar a cabo una investigacionmas a fondo. Este articulo identifica areas que requieren investiga-cion en el futuro incluyendo comparaciones entre los distintosmetodos y la introduccion de una variedad de concentraciones yaplicaciones multiples de los cuatro consolidantes examinados.

Biography

Kate Becker graduated from University College London, Institute ofArchaeology in 2014 with an MA in Principles of Conservation andan MSc in Conservation for Archaeology and Museums. In fulfil-ment of her degree, she completed two conservation student place-ments, the first at the Museum of London and the second at theBrooklyn Museum in New York. She has also worked for twoseasons as an on-site archaeological conservator in southern Turkey.

Materials and suppliersParaloid B72 and Klucel G:Preservation Equipment LtdVinces RoadDissNorfolk IP22 4HQUK

Lascaux Medium for Consolidation andLascaux JunFunori:Lascaux Colours & RestauroBarbara Diethelm AGZurichstrasse 42CH-8306 BruttisellenSwitzerland

Contact address

Kate BeckerArchaeological Conservationc/o Museum of London150 London WallLondon EC2Y 5HNUKEmail: katelmbecker@gmail.com

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