MATERIALS INFORMATION and TECHNICAL RESOURCES for ARTISTS - Rigid Supports There are pros and cons to all solid and flexible supports. Generally speaking, an ideal support will be able to withstand fluctuations in RH and temperature, possess an adequate level of absorbency and/or tooth, remain planar and resist warping, and not become brittle or fragile with age. One drawback often associated with flexible supports is that they are more susceptible to being damaged by physical impact (e.g. tears, impact cracks, punctures, etc.) Flexible supports made from cellulose like cotton and linen are more likely to respond to changes in the environment, giving rise to draws in the corners, an overall loss of tension, and other planar deformations. Such damages can lead to both short and long term condition issues and can affect the stability of the paint and ground layers. Because of these issues, artists are highly encouraged to affix protective backing boards to the reverse of their paintings. This helps to prevent physical impacts from the reverse and help to buffer and slow the fabric’s response to changes in humidity. Rigid supports made from hygroscopic materials like wood are less likely to withstand physical damage but will still react to changes in the environment (e.g. warping, cracking, etc.) which can adversely affect the ground and paint layers. There are steps that artists can take to mitigate some of these problems. One method is to adhere a fabric support over the face of the rigid panel. The fabric can serve as a less brittle interlayer which may stop the crack or split from telegraphing from the support to the ground and paint layers should the rigid support exhibit warping and/or cracking. Rigid supports can also be cradled or braced, particularly if they are large in size, to counteract possible warping or other types of planar deformations. RIGID SUPPORTS Many different solid support materials are available to artists. These materials include wood, metal, and modern composite materials. As there are pros and cons associated with any choice of solid support, artists should keep in mind the size, ground, and paint layers that will be applied when selecting and preparing their substrates. The following is information about a number of types of solid supports that are currently available to artists. Additional information on historical and contemporary practices relating to rigid supports is available in the section containing online resources and references. Solid Wood Panels For centuries painters have used hardwoods (from deciduous trees and narrow-leaved evergreens) and semi-hardwoods (partially matured cuttings from deciduous trees) including oak, mahogany, chestnut, and poplar have been used as
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MATERIALSINFORMATIONandTECHNICALRESOURCESforARTISTS-RigidSupports
Thereareprosandconstoallsolidandflexiblesupports.Generallyspeaking,anidealsupportwillbeabletowithstandfluctuationsinRHandtemperature,possessanadequatelevelofabsorbencyand/ortooth,remainplanarandresistwarping,andnotbecomebrittleorfragilewithage.
Onedrawbackoftenassociatedwithflexiblesupportsisthattheyaremoresusceptibletobeingdamagedbyphysicalimpact(e.g.tears,impactcracks,punctures,etc.)Flexiblesupportsmadefromcelluloselikecottonandlinenaremorelikelytorespondtochangesintheenvironment,givingrisetodrawsinthecorners,anoveralllossoftension,andotherplanardeformations.Suchdamagescanleadtobothshortandlongtermconditionissuesandcanaffectthestabilityofthepaintandgroundlayers.Becauseoftheseissues,artistsarehighlyencouragedtoaffixprotectivebackingboardstothereverseoftheirpaintings.Thishelpstopreventphysicalimpactsfromthereverseandhelptobufferandslowthefabric’sresponsetochangesinhumidity.
Rigidsupportsmadefromhygroscopicmaterialslikewoodarelesslikelytowithstandphysicaldamagebutwillstillreacttochangesintheenvironment(e.g.warping,cracking,etc.)whichcanadverselyaffectthegroundandpaintlayers.Therearestepsthatartistscantaketomitigatesomeoftheseproblems.Onemethodistoadhereafabricsupportoverthefaceoftherigidpanel.Thefabriccanserveasalessbrittleinterlayerwhichmaystopthecrackorsplitfromtelegraphingfromthesupporttothegroundandpaintlayersshouldtherigidsupportexhibitwarpingand/orcracking.Rigidsupportscanalsobecradledorbraced,particularlyiftheyarelargeinsize,tocounteractpossiblewarpingorothertypesofplanardeformations.RIGIDSUPPORTS
Manydifferentsolidsupportmaterialsareavailabletoartists.Thesematerialsincludewood,metal,andmoderncompositematerials.Asthereareprosandconsassociatedwithanychoiceofsolidsupport,artistsshouldkeepinmindthesize,ground,andpaintlayersthatwillbeappliedwhenselectingandpreparingtheirsubstrates.Thefollowingisinformationaboutanumberoftypesofsolidsupportsthatarecurrentlyavailabletoartists. Additionalinformationonhistoricalandcontemporarypracticesrelatingtorigidsupportsisavailableinthesectioncontainingonlineresourcesandreferences. SolidWoodPanels
Forcenturiespaintershaveusedhardwoods(fromdeciduoustreesandnarrow-leavedevergreens)andsemi-hardwoods(partiallymaturedcuttingsfromdeciduoustrees)includingoak,mahogany,chestnut,andpoplarhavebeenusedas
supports.Thelong-termageingpropertiesofsolidwoodpanelsdependonthetypeandcutofwood.Sapwoodistheoutermostportionofatreetrunk(thelivingpartofthetree),whileheartwoodisthetrunk’sinner(dead)core.Heartwoodismoresuitableforuseforpaintingsupportsasitshrinksandswellslessthansapwood.Allsolidwoodpanelsaresusceptibletosomedegreeofwarping,shrinkageorexpansion.Thiscanbelessenedbytheselectionofthemoreappropriatecutsofwood(radialratherthantangential),properpreparation(ageinganddrying)ofthewoodensupport,andthemethodoftreatment(finishingbothsidesofthepanelinasimilarmanner).Sometypesofwoodaremorelikelytoexperienceattacksbywood-boringinsects.Thisshouldbetakenintoconsiderationwhenselectingandpreparingawoodensupport.
Thestabilityofawoodenboardisgreatlyinfluencedbywhereitwascutfromtheoriginaltreetrunk.Woodexpandsandcontractsinthedirectionperpendiculartothegraindirection.Woodenboardstendtobemoststablewhentheyaremostsimilaronthefrontandback.Tangentiallysawnplanksarepronetoplanardeformationslikewarping,splitting,andcrackingastheseplanksoftencontainbothsapwoodandheartwoodandthenumberofgrainlinesareverydifferentonthefrontascomparedtotheback.Radiallysawnplanksaregenerallymorestable.Whenapanelsupportiscomprisedofmultipleplanks,theorientationofthewoodgrainhasaneffectonthestabilityofthepanel.Ifthegrainofadjoiningplanksisorientedperpendiculartooneanother,structuralproblemscanarisewhenthesupportexperiencesenvironmentalfluctuations.Therefore,ifmultipleplanksaretobejoinedtogether,alloftheplanksshouldhavethewoodgrainorientedinthesamedirection.Supportscreatedfrommultipleplankscandevelopsplitsandcracksalongthejoinswhensubjectedtoadverseenvironmentalconditions,andtensionbetweenthesectionsofthewoodcanresultincrackingorsplitting.Artistswhoworkonalargerscaleshouldkeepthisinmindwhenselectingand/orpreparingwoodenpanelsupports.
Whenartistsusewoodensupports,theyshould: • Consideringusingwell-seasonedhardwoodslikemahogany,maple,or
oak.Inspectthesurfaceofthepaneltoensurethatnoknots,cracks,orotherdeformationsarepresent.
• Useplanksthatareatleast2.5cm(1”)thick,asthinnerboardsaremorelikelytosufferstructuraldeformation.
• Avoidsemi-hardwoodsandsoftwoodslikepoplarandpinewhenpossible.Ifthesewoodsarechosen,itisrecommendedthattheybecoveredwithalayerofcanvastopreventthetransferofsplitsandcracksfromthesupporttothegroundandpaintlayers.Largerformatwoodensupportscomprisedofmultipleplanksshouldalsobecoveredwithcanvas(overallifpossibleoratleastusecanvasstripstocoverjoins/splits)tohelppreventthetransferofsplitsandcracksfromthesupporttothegroundandpaintlayers.
• Considersizing(andpossiblypriming)bothsidesofthesupportinordertomitigatepotentialwarpinginthefuture.Thisprocedureensuresthatbothsidesofthepanelwillrespondmoresimilarlytoenvironmentalchanges.PossiblesizingmaterialstoconsiderincludeneutralpHPVA,certainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels),andvarnishcoatings(e.g.Regalrez1094,MSAvarnishes,etc.).Refinedshellacandpolyurethanecoatingshavealsobeenusedtoeffectivelyreducetheabsorbencyofthesurfaceandtosealthewoodbutartistsshouldtakecarenottoapplythesematerialstoothickly.Shellacandpolyurethanearelessthanidealmaterialsintermsofreversibility,brittlenessandagingcharacteristics.
• Support-induceddiscoloration(SID)couldoccurifwater-solublematerialsmigratethroughthesize/sealantandsubsequentlystainthe
groundand/orpaintlayers(water-solublefractionsoftenincludetannins,starch-basedmaterials,etc.).TopreventSIDfromoccuring,considerapplyinganevencoatofneutralpHPVAadhesiveoracrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels)tothesurfaceofthepanelpriortoapplyingacrylicgrounds,oilgrounds,orfabric/paperinterleafs.Toadherecanvas/papertoapanel,thefollowingstepsarerecommended:
ApplyoneevencoatofPVAsizeoracrylicgelmediumtothesurfaceofthepanelusingaspatulaorabrush.Lightlywetthereverseofthecanvas(thesidethatwillbeadheredtothepanel)withwatertopromotebetteradhesion.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).ImmediatelyapplyanothercoatofPVAsizeoracrylicgelmedium(sticktothesamematerialyouusedpreviously)tothefaceofthecanvas.Oncethecanvashasdried,applyacoatofPVAsizeoracrylicgelmediumtothereverseofthepaneltopreventpotentialwarping.
• ItisalsopossibletouseBEVA371adhesive/filmtoadherecanvasto
panelafterthepanelhasbeensealed.BEVAfilm(asopposedtotheadhesive)willnotpenetratethefabricsupportasreadilyasPVAadhesiveand/oracrylicmediumsmightandtheabilitytore-activatetheadhesivemakesitfareasiertoeliminateanyunwantedair-bubbleslateronshouldtheyformduringtheprocess.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:
ApplyonetotwoevencoatsofdiluteBEVAadhesive(thincreamconsistency)tothepanelaftercleaningthesurfaceandtwocoatstothereverseofthecanvas(wearadequateprotectionassolventsarerequired).IfyouareusingBEVAfilmitisbettertousetwosheetsoffilmasopposedtoone,althoughonesheetmaybeabletoprovideenoughadhesion.PlacethefilmwiththeBEVA-sidefacingthepanel(orcanvasifyouareusingtwosheets)withoutremovingthesilicone-coatedMylarandapplyheatevenlyusinganiron(BEVAadhesiverequiresatemperatureofaround65.6degreesCelsiustobere-activated).WeightdownthesurfaceuntiltheBEVAhascooledandthencarefullypeelawaythesilicone-coatedMylar(NOTE:IfyouattempttoremovetheMylartoosoonyouwillpulluptheBEVA).Ifyouareusingtwosheets,repeatthisprocesswiththeothersheetofBEVAfilmwhenapplyingtothereverseofthecanvassupport(considerplacingsilicone-releasepaper/Mylarbeneaththecanvaswhenapplyingheat,siliconesidefacingup).ThenpositionyourcanvasdirectlyatoptheBEVAfilm,
placesilicone-releasepaper/Mylar(siliconesidefacingdown)atopthecanvas,andapplyheat.IfyouareusingBEVAadhesivesimplywaitforthecoatsofBEVAtodry(inawellventilatedspace)andrepeattheaforementionedstep.IfyouexperiencedifficultiesusingBEVAfilmtryapplyingacoatofadhesivetothebackofthecanvasorswitchtotheadhesivealtogether.
Considerusingatemperaturecontrolledvacuumtableifyouwishtoadhereacompletedpaintingontoapanel.Ingeneralthisisnotrecommendedandheat/pressureshouldbeavoidedentirelyifthepaintfilmisstillfairlyyoung.Itmaybepossibletosafelyadhereyourcompositionifitdoesnotcontainthicklybuiltuppaint,wax-basedadditives,orareasofstrongimpasto.Followtheinstructionsabovebutconsiderusingasoftblotterpaperoveryoursiliconereleasepaper/Mylartoprotectmoredelicatesurfaces(youmayalsoneedtoraisethetemperatureofyourironeversoslightly).
• Althoughrabbitskin/animalgluepossesseshygroscopicproperties,
manyartistscontinuetousethistraditionalmaterialasasizeand/oradhesive.NotethatitisNOTadvisabletoapplyacrylicand/orPVAsizetohardboards/fiberboardspriortoapplyingtraditionalglue-basedgessogroundsasthiscouldleadtopotentialdelamination.ToavoidanyissuesrelatingtoSIDhowever,artistsshouldconsideradheringfabrictothepanelsupportpriortoapplyingthegessoground.Toadhereyourcanvastoapanelusinganimalglue,thefollowingstepsarerecommended:
Prepareyouranimalgluefollowingthedirectionsonthepackage.Brushagenerous,evencoatofglueontothepanel’ssurface.Youmayallowthiscoattodrybeforecontinuingwiththeprocessorproceedimmediately.Wearingnitrilegloves,immersethecanvasintothetepidglue(makesurethatitisnotsohotastoburnyourhands),gentlywringthefabrictoremoveexcessglue.Positionthefabricontothepanel.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).Immediatelyapplyacoatofgluetothereverseofthepanel(NOTE:Itisnotadvisedtoleaveacoatofanimalglueexposedtotheenvironment.Subsequentlayersofprimingandpaintneedtobeappliedtothereverseinordertoavoidwarping,mimickingthesamelayeringusedonthefrontofthepanel).Allowforadequateandevendryingbystandingthepanelonitsedgeorleaningagainstawall.
• Provideadditionalauxiliarysupporttolargeformatpanelsandpanelsthatarelessthan¾”thickbyattachingabraceorcradlebygluingstripsofwoodaroundtheoutsideedgeofthebackofthepanelusingthefollowingsteps:
Obtain1”by2”woodenboards(oakormaplearepreferred)andcutthemdowntomatchtheouterdimensionsofthesupport(overallsizewilldependonwhattypeofjoinisusedforthecorners).Buttandmiteredtendtobethemostcommontypeofjoins(considerusinga90degree-cornerclampwhenmakingmiteredcorners),howeverlapjoinsaregenerallyconsideredtobemorestructurallysound.Makesurethatthewoodenboardsareperfectlyalignedandflushwiththeouteredgesbylayingthemonthereverseofthepanelbeforegluingtothereverse(itcanhelpfultomarkthepositionwithapencil).Usecarpenter’sgluetoadherethewoodenboardsinplaceWhiletheglueisdrying,clamp/weighttheboardstoavoidcreatinganyairbubbles.Forlarge-scalesupportsartistsmaychoosetoconstructhorizontaland/orverticalcrossbarsalthoughcrossbarsshouldNOTbeglueddirectlytothereverseofthepanel,onlyfixedtotheouterboardsofthecradleusingglueand/orhardware.
Plywood
Plywoodisalaminatedwoodproductthatispreparedbyadheringtogetherlayersofthinwoodveneer(plies)withthegrainofeachlayerpositionedatrightanglestothegrainoftheprecedinglayer.Sometypesofplywoodareavailablewithalumber,orsolidwood,core.
Diagram showing the alternating directional grain of a 5-ply, wooden
support. Some types of plywood are also available with a solid wood core.
Thecross-laminatestructureofplywood--particularlyifthepliesareallof
equalthickness--helpsensurethatthesupportislesspronetoplanardeformation.Plywoodcanbemadefromavarietyofsoftandhardwoods.Thelattertendstobemoredimensionallystable.Ingeneral,themorelayers,themoredimensionallystabletheplywoodsupport.Exterior-gradeplywoodhassuperiorresistancetomoisture,whileinterior-gradeplywoodhasthesmoothestsurfacefinish.
GatorfoamboardorGatorboardisnotplywood.itiscomposedofextrudedpolystyrenefoambondedbetweentwolayersofwood-fiberveneer.Itprovidesaveryrigidsurface,butthewood-fiberlayersmayrespondtochangesintheenvironment.
PlywoodandespeciallyGatorboardpanelsarenotconsideredsufficientlystableforpermanentuse.Artistsmaybeabletomitigatesomeoftheproblemsassociatedwiththesesubstratesbyconsideringthefollowingrecommendations:
• Inspectthesurfaceofplywoodtoensurethatarenoknots,cracks,or
otherdeformations.• Choosemaple,walnut,ormahoganyplywoodwhicharemoredurable
andstable(birchplywoodcanalsobeused,butthegrainhasatendencytotransferthroughtothegroundandpaintlayersovertime).
• Forlargerworkschooseplywoodthatisatleast¾”thickasthisexhibitsadequatedimensionalstability.
• PlywoodcanandGatorboardpanelsmaybenefitfromadheringafabriclayertothesurfacebeforepriming.Thesepanelsshouldbestoredflat.
• Considersizing(andpossiblypriming)bothsidesofthesupportinordertomitigatepotentialwarpinginthefuture.PossiblesizingmaterialstoconsiderincludeneutralpHPVA,certainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels),andvarnishcoatings(e.g.Regalrez1094,MSAvarnishes,etc.).Refinedshellacandpolyurethanecoatingshavealsobeenusedtoeffectivelyreducetheabsorbencyofthesurfaceandtosealthewoodbutartistsshouldtakecarenottoapplythesematerialstoothickly.Shellacandpolyurethanearelessthanidealmaterialsintermsofreversibility,brittlenessandagingcharacteristics.
• Support-induceddiscoloration(SID)couldoccurifwater-solublematerialsmigratethroughthesize/sealantandsubsequentlystainthegroundand/orpaintlayers(water-solublefractionsoftenincludetannins,starch-basedmaterials,etc.).TopreventSIDfromoccuring,considerapplyinganevencoatofneutralpHPVAadhesiveoracrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels)tothesurfaceofthepanelpriortoapplyingacrylicgrounds,oilgrounds,orfabric/paperinterleafs.Toadherecanvas/papertoapanel,thefollowingstepsarerecommended:
ApplyoneevencoatofPVAsizeoracrylicgelmediumtothesurfaceofthepanelusingaspatulaorabrush.Lightlywetthereverseofthecanvas(thesidethatwillbeadheredtothepanel)withwatertopromotebetteradhesion.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).ImmediatelyapplyanothercoatofPVAsizeoracrylicgelmedium(sticktothesamematerialyouusedpreviously)tothefaceofthecanvas.Oncethecanvashasdried,applyacoatofPVAsizeoracrylicgelmediumtothereverseofthepaneltopreventpotentialwarping.
• ItisalsopossibletouseBEVA371adhesive/filmtoadherecanvastopanelafterthepanelhasbeensealed.BEVAfilm(asopposedtotheadhesive)willnotpenetratethefabricsupportasreadilyasPVAadhesiveoracrylicmediumsmightandtheabilitytore-activatetheadhesivewithheatmakesitfareasiertolateraddressanyunwantedair-bubblesshouldtheyformduringtheprocedure.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:
ApplyonetotwoevencoatsofdiluteBEVAadhesive(thincreamconsistency)tothepanelaftercleaningthesurfaceandtwocoatstothereverseofthecanvas(wearadequateprotectionassolventsarerequired).IfyouareusingBEVAfilmitisbettertousetwosheetsoffilmasopposedtoone,althoughonesheetmaybeabletoprovideenoughadhesion.PlacethefilmwiththeBEVA-sidefacingthepanel(orcanvasifyouareusingtwosheets)withoutremovingthesilicone-coatedMylarandapplyheatevenlyusinganiron(BEVAadhesiverequiresatemperatureofaround65.6degreesCelsiustobere-activated).WeightdownthesurfaceuntiltheBEVAhascooledandthencarefullypeelawaythesilicone-coatedMylar(NOTE:IfyouattempttoremovetheMylartoosoonyouwillpulluptheBEVA).Ifyouareusingtwosheets,repeatthisprocesswiththeothersheetofBEVAfilmwhenapplyingtothereverseofthecanvassupport(considerplacingsilicone-releasepaper/Mylarbeneaththecanvaswhenapplyingheat,siliconesidefacingup).ThenpositionyourcanvasdirectlyatoptheBEVAfilm,placesilicone-releasepaper/Mylar(siliconesidefacingdown)atopthecanvas,andapplyheat.IfyouareusingBEVAadhesivesimplywaitforthecoatsofBEVAtodry(inawellventilatedspace)andrepeattheaforementionedstep.IfyouexperiencedifficultiesusingBEVAfilm,tryapplyingacoatofadhesivetothebackofthecanvasorswitchtotheadhesivealtogether.
Considerusingatemperaturecontrolledvacuumtableifyouwishtoadhereacompletedpaintingontoapanel.Ingeneralthisisnotrecommendedandheat/pressureshouldbeavoidedentirelyifthepaintfilmisstillfairlyyoung.Itmaybepossibletosafelyadhereyourcompositionifitdoesnotcontainthicklybuiltuppaint,wax-basedadditives,orareasofstrongimpasto.Followtheinstructionsabovebutconsiderusingasoftblotterpaperoveryoursiliconereleasepaper/Mylartoprotectmoredelicatesurfaces(youmayalsoneedtoraisethetemperatureofyourironeversoslightly).
• Althoughrabbitskin/animalgluepossesseshygroscopicproperties,
manyartistscontinuetousethistraditionalmaterialasasizeand/oradhesive.NotethatitisNOTadvisabletoapplyacrylicand/orPVAsizetohardboards/fiberboardspriortoapplyingtraditionalglue-basedgessogroundsasthiscouldleadtopotentialdelamination.ToavoidanyissuesrelatingtoSIDhowever,artistsshouldconsideradheringfabrictothepanelsupportpriortoapplyingthegessoground.Toadhereyourcanvastoapanelusinganimalglue,thefollowingstepsarerecommended:
Prepareyouranimalgluefollowingthedirectionsonthepackage.Brushagenerous,evencoatofglueontothepanel’ssurface.Youmayallowthiscoattodrybeforecontinuingwiththeprocessorproceedimmediately.Wearingnitrilegloves,immersethecanvasintothetepidglue(makesurethatitisnotsohotastoburnyourhands),gentlywringthefabrictoremoveexcessglue.Positionthefabricontothepanel.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).Immediatelyapplyacoatofgluetothereverseofthepanel(NOTE:Itisnotadvisedtoleaveacoatofanimalglueexposedtotheenvironment.Subsequentlayersofprimingandpaintneedtobeappliedtothereverseinordertoavoidwarping,mimickingthesamelayeringusedonthefrontofthepanel).Allowforadequateandevendryingbystandingthepanelonitsedgeorleaningagainstawall.
• Provideadditionalauxiliarysupporttolargeformatpanelsandpanelsthatarelessthan¾”thickbyattachingabraceorcradlebygluingstripsofwoodaroundtheoutsideedgeofthebackofthepanelusingthefollowingsteps:
Obtain1”by2”woodenboards(oakormaplearepreferred)andcutthemdowntomatchtheouterdimensionsofthesupport
(overallsizewilldependonwhattypeofjoinisusedforthecorners).Buttandmiteredtendtobethemostcommontypeofjoins(considerusinga90degree-cornerclampwhenmakingmiteredcorners),howeverlapjoinsaregenerallyconsideredtobemorestructurallysound.Makesurethatthewoodenboardsareperfectlyalignedandflushwiththeouteredgesbylayingthemonthereverseofthepanelbeforegluingtothereverse(itcanhelpfultomarkthepositionwithapencil).Usecarpenter’sgluetoadherethewoodenboardsinplaceWhiletheglueisdrying,clamp/weighttheboardstoavoidcreatinganyairbubbles.Forlarge-scalesupportsartistsmaychoosetoconstructhorizontaland/orverticalcrossbarsalthoughcrossbarsshouldNOTbeglueddirectlytothereverseofthepanel,onlyfixedtotheouterboardsofthecradleusingglueand/orhardware.
Hardboards,Fiberboards,etc.
Theterms“hardboard”and“fiberboard”areoftenusedinterchangeablydespitethefactthattheyaredifferentproducts.ThemajordifferencebetweenhardboardssuchasfiberboardpanelslikeMediumDensityFiberboardandHighDensityFiberboard(e.g.Masonite)isthewayinwhichtheyaremanufactured.
Hardboardpanelsaregenerallycreatedthroughawet/dryprocesswhich
reliesonnaturallypresentcellulosiclignininthewoodtocementthefiberstogether.Temperedhardboardsareimpregnatedwithanoilyorresinoussubstancemakingthemdarkerincolor(untemperedhardboardsareusuallyalightbrowncolor)andmoreresistanttomoistureandmechanicaldamage(andthereforesubsequentwarping,raisingoffibers,etc.)thanuntemperedhardboard.Masonite,oneofthemostcommonlymanufacturedhardboards,firstbegantobeusedforartisticpurposesinthelate1920s. Support-induceddiscoloration(SID)couldoccurifwater-solubleand/oroilyorresinousmaterialsmigratethroughthesizeorsealantandstainsthegroundand/orpaintlayers(water-solublefractionsoftenincludetannins,starch-basedmaterials,etc.).Today,mosttemperedhardboardsupportsarelesslikelytocauseSID-relatedissues,howeverartistsshouldconsiderexercisingcertainprecautionstopreventSIDdependingonthevariouspreparatorytechniquesthatareused(refertothelistofsuggestionsattheendofthissection).
Fiberboardpanelsarecreatedthroughadryprocessthatreliesonchemicalagentslikeurea-formaldehydetobindthewoodfiberstogether.HighDensityFiberboard(HDF)issuperiortoMediumDensityFiberboard(MDF)asithassignificantlyhigherinternalbondstrengthandislesssusceptibletomoisturedamage.However,HDFisstillpronetoplanardeformation.Propersealingorsizingandgroundapplicationcanmitigatethisproblem.
Clayboardsarehigh-densityfiberboardsthathavebeencoatedwithalayerrichinclay(kaolin).Becausetheclaylayerservesasastableground,clayboardsare
notpronetosupport-induceddiscoloration(SID).AmpersandArtSupplyisamajordistributorofclayboards(andothersolidsupportsforartists).
Theadvantagesoftheseboardsoverwoodarethattheyareavailableinlargesheets,havenograin(i.e.,nodirectionalmovement),andarenotassensitivetoclimaticchangesorattackbywood-boringinsects.Largesheetsdotendtowarpandtwistandcornerscanbecomebent,compressed,orexpanded.Untemperedhardboardsshouldnotbeusediflong-termpreservationisaconcern.Untemperedhardboardwasoncepreferredovertemperedduetotheearlieruseofsubstantialamountsofoilincorporatedintotheearliertemperingformulationswhichcouldmaketheminappropriateasasurfacetoreceivewatercontaininggrounds.Highqualityhardboardspurchasedfromrespectedsuppliersdonotsufferfromthisdefect. Whenartistschoosetousethesesupports,theyshould:
• Degreasethesurfacewithdenaturedalcoholbeforeapplyinglayersofsize,ground,and/orpaint.Withoutthispreparation,groundlayersmaynotadheretothesmoothsideofthesesupportsbecauseofsurfaceresidessuchasparaffinwaxthatmaybeleftduringthemanufacturingprocess.
• Gentlysandthefaceofthepanelwithfinesandpaper(e.g.220grit)toprovideaslightmechanicaltoothbutbecarefultonotoverlyroughenthesurfaceandunevenlyexposethewoodfibers.Thiscanleadtoirregularswellingofthesubstrate(particularlywhenwater-basedsizes,sealantsand/orpriming/groundareapplied).
• Considersizing(andpossiblypriming)bothsidesofthesupportinordertomitigatepotentialwarpinginthefuture.ThisstepcanalsohelptocounteractSID-relatedissues.PossiblesizingmaterialstoconsiderincludeneutralpHPVA,certainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels),andvarnishcoatings(e.g.Regalrez1094,MSAvarnish,etc.).Refinedshellacandpolyurethanecoatingshavealsobeenusedtoeffectivelyreducetheabsorbencyofthesurfaceandtosealthewoodbutartistsshouldtakecarenottoapplythesematerialstoothickly.Shellacandpolyurethanearelessthanidealmaterialsintermsofreversibility,brittlenessandagingcharacteristics.
• ConsiderapplyinganevencoatofneutralpHPVAadhesiveorcertainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels)whenadheringcanvas/papertothesurfaceofapanelfollowingdegreasing/cleaningofthesurface(aswithsizingalone,thisstepcanalsohelptocounteractSID-relatedissues).Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:
ApplyoneevencoatofPVAsizeoracrylicgelmediumtothesurfaceofthepanelusingaspatulaorabrush.Lightlywetthereverseofthecanvas(thesidethatwillbeadheredtothepanel)
withwatertopromotebetteradhesion.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).ImmediatelyapplyanothercoatofPVAsizeoracrylicgelmedium(sticktothesamematerialyouusedpreviously)tothefaceofthecanvas.Oncethecanvashasdried,applyacoatofPVAsizeoracrylicgelmediumtothereverseofthepaneltopreventpotentialwarping.
• ConsiderusingBEVA371adhesive/filmtoadherecanvastopanelafterthepanelhasbeensealed.BEVAfilm(asopposedtotheadhesive)willnotpenetratethefabricsupportasreadilyasPVAadhesiveoracrylicmediumsmightandtheabilitytore-activatetheadhesivewithheatmakesitfareasiertolateraddressanyunwantedair-bubblesshouldtheyformduringtheprocedure.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:
ApplyonetotwoevencoatsofdiluteBEVAadhesive(thincreamconsistency)tothepanelaftercleaningthesurfaceandtwocoatstothereverseofthecanvas(wearadequateprotectionassolventsarerequired).IfyouareusingBEVAfilmitisbettertousetwosheetsoffilmasopposedtoone,althoughonesheetmaybeabletoprovideenoughadhesion.PlacethefilmwiththeBEVA-sidefacingthepanel(orcanvasifyouareusingtwosheets)withoutremovingthesilicone-coatedMylarandapplyheatevenlyusinganiron(BEVAadhesiverequiresatemperatureofaround65.6degreesCelsiustobere-activated).WeightdownthesurfaceuntiltheBEVAhascooledandthencarefullypeelawaythesilicone-coatedMylar(NOTE:IfyouattempttoremovetheMylartoosoonyouwillpulluptheBEVA).Ifyouareusingtwosheets,repeatthisprocesswiththeothersheetofBEVAfilmwhenapplyingtothereverseofthecanvassupport(considerplacingsilicone-releasepaper/Mylarbeneaththecanvaswhenapplyingheat,siliconesidefacingup).ThenpositionyourcanvasdirectlyatoptheBEVAfilm,placesilicone-releasepaper/Mylar(siliconesidefacingdown)atopthecanvas,andapplyheat.IfyouareusingBEVAadhesivesimplywaitforthecoatsofBEVAtodry(inawellventilatedspace)andrepeattheaforementionedstep.IfyouexperiencedifficultiesusingBEVAfilm,tryapplyingacoatofadhesivetothebackofthecanvasorswitchtotheadhesivealtogether.Considerusingatemperaturecontrolledvacuumtableifyouwishtoadhereacompletedpaintingontoapanel.Ingeneralthisisnotrecommendedandheat/pressureshouldbeavoidedentirelyifthepaintfilmisstillfairlyyoung.Itmaybepossibletosafelyadhere
yourcompositionifitdoesnotcontainthicklybuiltuppaint,wax-basedadditives,orareasofstrongimpasto.Followtheinstructionsabovebutconsiderusingasoftblotterpaperoveryoursiliconereleasepaper/Mylartoprotectmoredelicatesurfaces(youmayalsoneedtoraisethetemperatureofyourironeversoslightly).
• Althoughrabbitskin/animalgluepossesseshygroscopicproperties,
manyartistscontinuetousethistraditionalmaterialasasizeand/oradhesive.NotethatitisNOTadvisabletoapplyacrylicand/orPVAsizetohardboards/fiberboardspriortoapplyingtraditionalglue-basedgessogroundsasthiscouldleadtopotentialdelamination.ToavoidanyissuesrelatingtoSIDhowever,artistsshouldconsideradheringfabrictothepanelsupportpriortoapplyingthegessoground.Toadhereyourcanvastoapanelusinganimalglue,thefollowingstepsarerecommended:
Prepareyouranimalgluefollowingthedirectionsonthepackage.Brushagenerous,evencoatofglueontothepanel’ssurface.Youmayallowthiscoattodrybeforecontinuingwiththeprocessorproceedimmediately.Wearingnitrilegloves,immersethecanvasintothetepidglue(makesurethatitisnotsohotastoburnyourhands),gentlywringthefabrictoremoveexcessglue.Positionthefabricontothepanel.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).Immediatelyapplyacoatofgluetothereverseofthepanel(NOTE:Itisnotadvisedtoleaveacoatofanimalglueexposedtotheenvironment.Subsequentlayersofprimingandpaintneedtobeappliedtothereverseinordertoavoidwarping,mimickingthesamelayeringusedonthefrontofthepanel).Allowforadequateandevendryingbystandingthepanelonitsedgeorleaningagainstawall.
• Provideadditionalauxiliarysupporttolargeformatpanelsandpanelsthatarelessthan¾”thickbyattachingabraceorcradlebygluingstripsofwoodaroundtheoutsideedgeofthebackofthepanelusingthefollowingsteps:
Obtain1”by2”woodenboards(oakormaplearepreferred)andcutthemdowntomatchtheouterdimensionsofthesupport(overallsizewilldependonwhattypeofjoinisusedforthecorners).Buttandmiteredtendtobethemostcommontypeofjoins(considerusinga90degree-cornerclampwhenmakingmiteredcorners),howeverlapjoinsaregenerallyconsideredtobe
morestructurallysound.Makesurethatthewoodenboardsareperfectlyalignedandflushwiththeouteredgesbylayingthemonthereverseofthepanelbeforegluingtothereverse(itcanhelpfultomarkthepositionwithapencil).Usecarpenter’sgluetoadherethewoodenboardsinplaceWhiletheglueisdrying,clamp/weighttheboardstoavoidcreatinganyairbubbles.Forlarge-scalesupportsartistsmaychoosetoconstructhorizontaland/orverticalcrossbarsalthoughcrossbarsshouldNOTbeglueddirectlytothereverseofthepanel,onlyfixedtotheouterboardsofthecradleusingglueand/orhardware.
LaminatedPaperBoardsandMuseumBoards
PaperboardsmadefromwoodwasteorwoodpulparesoldunderavarietyoftradenamesincludingUpsonBoardandBeaverBoard.Laminatedpaperboardsshouldbethoughtofastemporarysupports.Theyarehighlyacidicandhaveaweakphysicalstructure,sotheydeterioratequickly.Museumboardisahighqualitylaminatedpaperboardmadeof100%cottonragmatboard.Museumboardshavebetweentwoandeightdistinctlayers.Asmuseumboardlacksstructuralstrength,forincreasedrigidityitshouldbemountedonawoodenauxiliarybraceorpanel.CanvasBoards
Canvasboardsareconstructedfromathinlayerofcottonormuslinprimedwithanacrylicdispersiongroundthathasbeengluedtoasheetofpulpcardboard.Theseboardsshouldnotbeusediflong-termpreservationisaconcern.
Aluminum
Aluminumpanels,AluminumCompositeMaterial(ACM)panels,aluminumhoneycombpanels,andDibondpanelshavebeenwidelyusedbyartistssincethelate1940s.Aluminumismoreresistanttocorrosionthanothermetals,canbecuteasilywithabandsaw,and,dependingonthesizeandthicknessofthepanel,willretainstiffness.Itisnecessarytonotethat,eveninastableenvironment,thinnerpiecesofaluminumwillnotremainplanar.
ACMboardsdifferbymanufacturerbutaretypicallycomposedofathermoplasticcoresandwichedbetweentwolightweightsheetsofaluminum.Theseboardscanbepurchasedwithtwosidesofexposedaluminumandnopreparatorylayer,withacanvasmountedtoonesideandamill(polishedaluminum)finishonthereverse,orwithonesidecoatedwithawhitepolyestercoilfinishtoprotectthesurfaceagainstcorrosion.
ArtefexACMPanelsarecomprisedoftwosheetsof3mmaluminumbondedtoasolidpolyethylenecore.Theycanbepurchasedwithorwithoutapreparatorylayerandwithorwithoutonesidecoveredwithcanvas.DibondACMPanelsare
madeoftwolightweightsheetsof.010”aluminumwithathermoplasticcore.Theyareavailableinavarietyofcolors.
TheadvantagesofACMpanelsoverwoodorstretchedcanvasarethattheydonotrespondasreadilytochangesinRHandarenotpronetoinsectdamage.
Diagram showing the typical layering structure of an Aluminum Honeycomb
Panel.
Diagram showing an example of the layering structure of an Aluminum
Composite Panel (ACM).
Artistswhochoosetousethesesupportsshould:• Preparethealuminum/ACMsurfacesbyremovingtheprotectivefilm.
Degreasingthepresentationside(typicallythesidecoatedwithpolyester)withethanolorisopropanol.Createatooth(e.g.320gritsandpaper)bylightlyrougheningthesurfacewithanabrasivematerialNOTE:Ifawhiteprotectivepolyestercoilcoatingispresentavoidbreakingcompletelythroughitasthisexposestheunderlyingaluminumandcanleadtocorrosion.
• AvoidACMpanelsthatdonothaveapolyestercoilcoating(inindustryACMpanelscanbecoatedwitharangeofmaterials).
• Chooseapriming/groundmaterialcarefully.Priming/groundmaterialsthatareavailableinindustrymaybeacceptableiftheyhavebeenfoundtobecompatiblewithcertainACMbrands(Example:DTMBondingPrimerbySherwinWilliamshasbeenfoundtobehighlycompatiblewithDibondpanels).Aswithmostindustryproducts,artistsareencouragedtotestthesematerialswiththeirpreferredpaintingtechnique.
• FixthinnersupportstomorerigidsupportssuchasMasoniteorconstructacradle(seeinstructionsbelow).Sheetsthataretoothinaremorepronetodamageastheymayflexandtwistduringtransportationandhandling.
• Rememberthat“fatoverlean”principlesshouldbefollowedwhenapplyingalkyd,acrylics,and/oroilpaints.
• UnderstandthatACMpanelswithhoneycomborcorrugatedplasticcores(suchasArtefex)tendtobelighterinweightthanACMpanelsthatcontainsolidplasticcores.
• Avoidsubjectingthepaneltoextremelyhightemperatures(above175F). • Knowthatsupportsthatarefairlyheavyareatriskofplanardeformation
alongtheouteredges(e.g.bentcorners)especiallyduringtransportationandhandling.
• Avoidpaintingdirectlyonthesurfaceofunprimedaluminumasthistechniquecanleadtoadhesionproblems.
• ConsiderapplyinganevencoatofneutralpHPVAadhesiveorcertainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels)whenadheringcanvas/papertothesurfaceofapanelfollowingdegreasing/cleaningofthesurface.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:
ApplyoneevencoatofPVAsizeoracrylicgelmediumtothesurfaceofthepanelusingaspatulaorabrush.Lightlywetthereverseofthecanvas(thesidethatwillbeadheredtothepanel)withwatertopromotebetteradhesion.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).ImmediatelyapplyanothercoatofPVAsizeoracrylicgelmedium(sticktothesamematerialyouused
previously)tothefaceofthecanvas.Oncethecanvashasdried,applyacoatofPVAsizeoracrylicgelmediumtothereverseofthepaneltopreventpotentialwarping.
• ConsiderusingBEVA371adhesive/filmtoadherecanvastopanelafterthepanelhasbeensealed.BEVAfilm(asopposedtotheadhesive)willnotpenetratethefabricsupportasreadilyasPVAadhesiveoracrylicmediumsmightandtheabilitytore-activatetheadhesivewithheatmakesitfareasiertolateraddressanyunwantedair-bubblesshouldtheyformduringtheprocedure.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:
ApplyonetotwoevencoatsofdiluteBEVAadhesive(thincreamconsistency)tothepanelaftercleaningthesurfaceandtwocoatstothereverseofthecanvas(wearadequateprotectionassolventsarerequired).IfyouareusingBEVAfilmitisbettertousetwosheetsoffilmasopposedtoone,althoughonesheetmaybeabletoprovideenoughadhesion.PlacethefilmwiththeBEVA-sidefacingthepanel(orcanvasifyouareusingtwosheets)withoutremovingthesilicone-coatedMylarandapplyheatevenlyusinganiron(BEVAadhesiverequiresatemperatureofaround65.6degreesCelsiustobere-activated).WeightdownthesurfaceuntiltheBEVAhascooledandthencarefullypeelawaythesilicone-coatedMylar(NOTE:IfyouattempttoremovetheMylartoosoonyouwillpulluptheBEVA).Ifyouareusingtwosheets,repeatthisprocesswiththeothersheetofBEVAfilmwhenapplyingtothereverseofthecanvassupport(considerplacingsilicone-releasepaper/Mylarbeneaththecanvaswhenapplyingheat,siliconesidefacingup).ThenpositionyourcanvasdirectlyatoptheBEVAfilm,placesilicone-releasepaper/Mylar(siliconesidefacingdown)atopthecanvas,andapplyheat.IfyouareusingBEVAadhesivesimplywaitforthecoatsofBEVAtodry(inawellventilatedspace)andrepeattheaforementionedstep.IfyouexperiencedifficultiesusingBEVAfilm,tryapplyingacoatofadhesivetothebackofthecanvasorswitchtotheadhesivealtogether.Considerusingatemperaturecontrolledvacuumtableifyouwishtoadhereacompletedpaintingontoapanel.Ingeneralthisisnotrecommendedandheat/pressureshouldbeavoidedentirelyifthepaintfilmisstillfairlyyoung.Itmaybepossibletosafelyadhereyourcompositionifitdoesnotcontainthicklybuiltuppaint,wax-basedadditives,orareasofstrongimpasto.Followtheinstructionsabovebutconsiderusingasoftblotterpaperoveryoursiliconereleasepaper/Mylartoprotectmoredelicatesurfaces(youmayalsoneedtoraisethetemperatureofyourironeversoslightly).
• Provideadditionalauxiliarysupporttolargeformatpanelsandpanels
thatarelessthan¾”thickbyattachingabraceorcradlebygluingstripsofwoodaroundtheoutsideedgeofthebackofthepanelusingthefollowingsteps:
Obtain1”by2”woodenboards(oakormaplearepreferred)andcutthemdowntomatchtheouterdimensionsofthesupport(overallsizewilldependonwhattypeofjoinisusedforthecorners).Buttandmiteredtendtobethemostcommontypeofjoins(considerusinga90degree-cornerclampwhenmakingmiteredcorners),howeverlapjoinsaregenerallyconsideredtobemorestructurallysound.Makesurethatthewoodenboardsareperfectlyalignedandflushwiththeouteredgesbylayingthemonthereverseofthepanelbeforegluingtothereverse(itcanhelpfultomarkthepositionwithapencil).Useanappropriateadhesive(pleaserefertotheDibondManuallocatedinourreferencesection)toadherethewoodenboardsinplacewhiletheglueisdrying,clamp/weighttheboardstoavoidcreatinganyairbubbles.Forlarge-scalesupportsartistsmaychoosetoconstructhorizontaland/orverticalcrossbarsalthoughcrossbarsshouldNOTbeglueddirectlytothereverseofthepanel,onlyfixedtotheouterboardsofthecradleusingglueand/orhardware.
Copper
Artistshaveusedcoppersupportssincethe17thcenturyforbothpracticalandaestheticreasons.Copperpanelsaredurableandcompactandareavailableinarangeofportablesizesbutaremorepronetocorrosionthanaluminum.Acoppersupporttendstogiveawarmtonetotheoverallcompositionasoilpaintsdonotsinkintothegroundastheydooncanvasorwoodenpanelssotheycanremainintenselysaturatedevenwhenappliedinthinlayers.Artistswhochoosetousecoppersupportsshould:
•Preparethesurfacebydegreasingthepresentationsidewithsolvents(e.g.mineralspiritsfollowedbydenaturedalcohol)andcreatingatoothbyrougheningthesurfacewithanabrasivematerial.NOTE:Thereisnoneedtopurchasecostlier“polished”copperetchingplatesasartistsareencouragedtoabradethesurfaceanyhowtoimproveadhesion.
• Sheetsthataretoothinaremorepronetodamageastheycanflexandtwistduringtransportationandhandling.Selectcopperpanelsthatareofanappropriatethickness(e.g.highqualitycopperetchingplates).
•Fix/adherethinnersupportstomorerigidsupportssuchasMasonitebygloballyapplyinganadhesivelikeepoxyinanevenmannertothesheet
and/ortherigidsupport(abradethereverseofthepanelpriortogluingtoimproveadhesion).Ingeneral,however,thingaugecopperpanelsshouldbeavoided.
•Rememberthat“fatoverlean”principlesshouldbefollowedwhenapplyingalkyd,acrylics,and/oroilpaints.
•Avoidaqueous-basedground/paintmaterialsinordertopreventtheformationofcorrosionproducts.
•Notpaintdirectlyonthesurfaceofunprimedcopperasthistechniquemayleadtopotentialadhesionproblemsinthefuture.
OtherMetalSupports
Tin,tin-platediron,steel,zinc,andothermetalshaveoccasionallybeenusedbyartistsassupports.Tin-containingsupportsaresusceptibletocorrosionwhenexposedtohighhumidity,oxygen,andatmosphericpollutants.Zincsupportsarelesspronetocorrosioninhumidenvironmentsthancoppersupports,buttheyaremoresusceptibletodegradationwhenexposedtoacidicoralkalinematerialsandconditions.Athintransparentfilmofzincoxide(whichappearsasabluish-whitefilm)canformonazincpanelwhenitisexposedtoair.Thezincoxidethencanreactwithfattyacidsinoilandalkydpaintstoformzincsoaps(whichmayprotrudethroughthesurfaceasunsightlypustules).Steelandstainlesssteelarenotcommonlyusedassupportsduetotheweightofthesemetalalloys.Steeliscomposedofironandcarbonwithsmalleradditionsofothermetallicelementssuchasmolybdenum,manganese,copper,chromium,ornickel.Thelargerpercentageofchromiuminstainlesssteel(aminimumof10.5%bymass)iswhatgivesitcorrosionresistance.
Slate/Stone/Marble/Porphyry
Itislikelythatvariousstoneshavebeenusedaspaintingsubstratessinceantiquity.Stonesormarblesthathaveafinegrain(arenotporous)andcanbeevenlypolishedarethemostsuitableforuseaspaintingsupports.Stonesupportsaremechanicallystableastheydonotchangewithhumidityfluctuationsandareimpervioustowormsandinsects.Brittleness,poorpreparationofthesurface,andpoorapplicationofthepaintandgroundlayers(e.g.deviatingfromthefatoverleanprinciple)cancausedelamination.Glass
Glasssupportssharethemechanicalstabilityandinsectresistanceofstonesupports,butpossessahighlyfinished,non-poroussurface.However,glassisinherentlyfragileandpronetobreakage(particularlyaroundtheouteredges)andcanbecomemorebrittleasitsages.Aspaintandgroundlayerscanreadilydelaminateduetotheslicksurface,glasssupportsarenotrecommended.Ifartists
choosetouseglasssupports,onlyfrostedorsandblastedglassshouldbeusedandthesurfaceshouldbedegreasedwithethanoloracetonebeforeuse. Polyvinylchloride
Themainissuewiththeuseofpolyvinylchloride-basedplasticsaspaintingsupportsisthepossiblepresenceofplasticizersandotheradditiveswhichmightbeaddedduringthemanufacturingprocess.Withouttesting,itisdifficulttoidentifythespecificpolymerblendspresentwithinapolyvinylchloride(PVC)sheetortoknowhowstablethematerialis.Overtime,anyplasticizersthatmightbepresentinaPVCsheetcanmigratetothesurfaceformingvisibleliquiddropswhichbecometackyandthencrystalline.Thepotentialmigrationofplasticizerscould,inturn,causedelaminationofthepaintand/orgroundlayers.SheetsofPVCcanwarpandwillsometimesgrowmoldwhenexposedtohighlevelsofhumidityandheat.Withoutfurtherstudy,polyvinylchloridecannotberecommendedasapermanentsupportforworksofart.
IftheartistinsistsonusingaPVCsupport,thebestprocedureistopaintonaproperlyprimedcanvasandadherethefinishedcanvastotheplasticsheet.Thisway,iftheplasticsupportdeteriorates,thecanvascanberemovedandadheredtonewsupport. Polycarbonate(e.g.Lexan)
Likepolyvinylchloride-basedplastics,polycarbonatesalsotendtocontainawiderangeofadditivesthatcanposepotentialproblemsforartists.Polycarbonatesarelong-chainlinearpolyestersofcarbonicacidanddihydricphenols(e.g.BisphenolA).Thereareseveralgradesofpolycarbonatesheetingavailabletodayanddistinguishingonefromanotherreallydependsontheadditivespresentwhichcanincludeglassfibers,UVstabilizers,moldreleaseagents,andflameretarders.Thepresence/absenceofthesestabilizerswillinturnaffectthepolycarbonate’sresistancetoheat,itsbrittleness,anditstendencytodegradeinUVlight.Polycarbonatecanalsobeincrediblysensitivetocertainsolvents;artistsshouldavoidbringingacetone,aromatics,andothersolventstosurfaceofPlexiglass,stickinginsteadtowaterormineralspirits-basedproducts.
Theprimaryconcernregardingtheseadditivesistheirtendencytomigrateoutofthesubstrateslowlyovertime(orquicklydependingonthenatureoftheenvironment).Forexample,themigrationofBisphenol-Ainclearpolycarbonateplastics(e.g.waterbottles)hasbeenextensivelystudied,aphenomenonthatcouldverylikelycausedelaminationand/orflakingoftheoverlyingground/paintlayers.Itisforthisreasonthatpolycarbonatesupportsarenotrecommendedforartworksthatareintendedtolast.
PolymethylMethacrylate(e.g.Plexiglas)
Plexiglassisoneofseveraltrademarkednamesusedtomarketclearsheetsofpolymethylmethacrylate,amaterialthatisapopularsupportamongartists.Thesesheetstendnottocontainpotentiallyproblematicadditivessuchasthosefoundinpolyvinylchloride-andpolycarbonate-basedmaterials.However,Plexiglasswillexpandandcontractinresponsetochangesintemperatureandhumidity,leadingtoeventualwarpingorbendingofthesupport.Thiscanbeproblematicifverybrittlematerialsareusedinthepaintand/orgroundlayers(e.g.oils,alkyds,certainresins)asdelaminationandcrackingmayoccurasthesupportexpandsandcontracts.Watercolors,tempera,andmostgouachepaintsshouldbeavoided.Theglassy-likesurfaceofPlexiglassmakesforasurfacethatcanbeeasilyscratchedandcanbuildupastaticchargethatcanattractdustparticles.PlexiglassispronetoyellowingifexposedtoUVlightandcanbeextremelysensitivetocertainsolvents;artistsshouldavoidbringingacetone,aromatics,andothersolventstosurfaceofPlexiglas,stickinginsteadtowaterormineralspirits-basedproducts.Finally,andperhapsmostimportantly,Plexiglasssupportsareinherentlybrittleandeasilyshatterorcrackifdroppedordamaged.
Ifanartistinsistsonusingapolymethylmethacrylatesupport,thebestprocedureistoinitiallysandthesurfaceinordertoprovidesomemechanicaltoothtoimprovetheadhesionofthepaintandgroundlayers.ArtistsshouldconsiderpaintingandprimingwithacrylicsifusingPlexiglassastheydoretainsomedegreeofflexibility.AvoidinstallinginflexiblehardwaredirectlyintothePlexiglass,choosethickerratherthanthinnersheets,anduseachanneledframetohouse/displaythePlexiglass. ADDITIONALREFERENCESANDRESOURCESGeneral“”Supports”inThePainter'sHandbook:RevisedandExpandedbyMarkDavidGottsegen(NewYork:Watson-Guptill,2006).“HistoryandUseofPanelsorOtherRigidSupports”byJorgenWadumandNoelleStreetoninTheConservationofEaselPaintings,eds.Dr.JoyceHillStonerandRebeccaRushfield(LondonandNewYork:Routledge,2012).GoldenArtistColors-PreparingaPaintingSupporthttp://www.goldenpaints.com/technicalinfo_prepsuppGoldenArtistColors–UnderstandWoodSupportsforArt–ABriefHistoryhttp://www.justpaint.org/understanding-wood-supports-for-art-a-brief-history/CAMEO:ConservationandArtMaterialsEncyclopediaOnline(MuseumofFineArtsBoston)http://cameo.mfa.org/wiki/Main_Page
WoodKressTechnicalArtHistoryWebsite-WoodenSupportshttps://www.artcons.udel.edu/about-us/kress/historical-materials-techniques/wooden-supports GoldenArtistsColors-UnderstandingWoodSupportsforArt-ABriefHistorybyElaineSalazarhttp://oldsite.goldenpaints.com/justpaint/jp29article3.php Britannica–WoodSciencehttp://www.britannica.com/science/wood-plant-tissue TransportInformationServices–PropertiesofVariousWoodSpecieshttp://www.tis-gdv.de/tis_e/misc/holzart.htmTheEncyclopediaofWood,U.S.DepartmentofAgriculture,2007[portionsavailable]https://books.google.com/books?id=qxQnAgAAQBAJ&pg=PT354&lpg=PT354&dq=%E2%80%A2+The+Encyclopedia+of+Wood,+USDA&source=bl&ots=MYUmCSV66b&sig=xUESVua9_cPCeLrPxf08t7N_2fQ&hl=en&sa=X&ved=0ahUKEwjard7PxZnOAhUCNSYKHbvzBaMQ6AEIcjAJ#v=onepage&q=%E2%80%A2%20The%20Encyclopedia%20of%20Wood%2C%20USDA&f=false]
Hardboard,Fiberboard,etc.JournaloftheAmericanInstituteforConservation(JAIC)-“Shortcommunicationearlywood-fiberpanels:Masonite,hardboard,andlower-densityboards”byAlexanderW.Katlanhttp://cool.conservation-us.org/jaic/articles/jaic33-03-005.htmlGoldenArtistsColors-PlywoodasaSubstrateforPaintinghttp://oldsite.goldenpaints.com/justpaint/jp29article4.phpAndhttp://www.justpaint.org/plywood-as-a-substrate-for-painting/Ampersand-PaintingPanelsforArtistshttp://www.ampersandart.com/products_main.htmlAmericanHarboatdAssociation-Today’sHardboardhttp://domensino.com/aha/images/tdyhdbrd.pdfCompositePanelAssociationhttp://www.compositepanel.org/CompositePanelAssociation-MDFFromStarttoFinishhttp://www.hardwoods-inc.com/sites/default/files/mdf_start_to_finish_2005.pdf
“Wood-basedCompositesandPanelProducts”byJohnA.YoungquistinForestProductsLaboratory*Madison,WI:I.S.DepartmentofAgriculture,1999)http://www.carbeck.org/pdfs/FPL_Wood_Handbook_Ch10.pdfPanelProcessing,Inc.–“Hardboard(Masonite)Whatisit?”byRMGranumandO.B.Eustishttps://harborsales.net/Portals/0/docs/hardboard_what_is_it.pdfAluminumDibondFabricationManualhttp://graphicdisplayusa.com/downloads/Dibond%20Fabrication%20Manual_May%202011.pdfGraphicDisplay,USA-Dibondhttp://graphicdisplayusa.com/products/dibond/NaturalPigments-ArtefexACMpanelshttp://www.naturalpigments.com/custom-artefex-panel.htmlJackson’s-AluminumPaintingPanelshttps://www.jacksonsart.com/blog/2014/03/28/aluminium-painting-panels/SOSGraphics–SubstrateListhttp://www.sosgraphics.ca/SOSMaterialList.pdfCopperCopperasCanvas:TwoCenturiesofMasterpiecePaintingsonCopper,1575–1775,ed.byMichaelK.Komanecky(Oxford:OxfordUniversityPress,1998).Plastics,etc.GoldenArtistColors–AcrylicsonPlasticshttp://www.justpaint.org/acrylics-on-plasticsSOSGraphicsSubstrateListhttp://www.sosgraphics.ca/SOSMaterialList.pdfPolycarbonatesandotherplasticshttp://www.ptsllc.com/intro/polycarb_intro.aspxPlexiglashttp://www.plexiglas.com/export/sites/plexiglas/.content/medias/downloads/sheet-docs/plexiglas-general-information-and-physical-properties.pdfPlasticsinArt:AStudyfromtheConservationPointofView,byFriederikeWaentig(Petersberg:Imhof.,2008).
PlasticsinArt:History,Technology,Preservation,byTheavanOosten,YvonneShashoua,andFriederikeWaentig(Munich:Siegl,2002).
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