Application of reflected light microscopy for non-invasive wood identification of marquetry furniture and small wood carvings

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Available

online

at

ScienceDirect

www.sciencedirect.com

Original

article

Application

of

reﬂected

light

microscopy

for

non-invasive

wood

identiﬁcation

of

marquetry

furniture

and

small

wood

carvings

Flavio

Rufﬁnatto

a,∗

_,

_Corrado

_Cremonini

a,1

_,

_Nicola

_Macchioni

b,2

_,

_Roberto

_Zanuttini

a,3

a_Department_of_{Agricultural,}_Forestry_and_Food_Sciences_(DiSAFA),_Via_Leonardo_da_Vinci_44,₁₀₀₉₅_Grugliasco,_Torino,_Italy

b_{CNR–IVALSA,}_Istituto_per_la_{valorizzazione}_del_legno_e_delle_specie_arboree,_via_Madonna_del_Piano_10,₅₀₀₁₉_Sesto_Fiorentino,_Firenze,_Italy

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received15May2013 Accepted26November2013 Availableonline24December2013 Keywords:

Reﬂectedlightmicroscopy IAWAlist

SavoiaRoyalHouse

Non-invasivewoodidentiﬁcation Antiques

a

b

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Woodidentificationisabasicinformationthatshouldinterestanywoodenartefact.Thistypicallyinvolves invasivesampling,butsometimessamplingisunattainableeitherbecauseoftheobjecttypologyor becauseitisdifficulttoobtainauthorizations.Inthepresentstudy,reflectedlightmicroscopypotential asanon-invasiveidentificationtoolforwoodenculturalartefactsisassessedonanumberofmarquetry furnitureandsmallwoodcarvings.Inmorethanonehalfofthe13examinedcasesaccuratewood identifi-cationwaspossible,whiletheremainingcasesyieldedinformationofdiagnosticvalue,makingitpossible toexcludeseveralpotentialcandidatespecies.Inanumberofcasestheuseofopticalfiltersimproved thevisibilityofcharacterstates.Shapeandorientationofsurfacesinfluencedthevisibilityofmicroscopic characters.Thestudyconfirmsthatreflectedlightmicroscopyisavaluabletoolfornon-invasivewood identification.Inmanycasesitisabletosupportaccurateidentification,inothersitcananywayprovide importantinformation,usefultohelpdecisionaboutsupposedspecies,ortolimittheinvasivenessof possiblefurtheranalysisbyaddressingthemonspecificfeatures.

Thepurposeofthisworkistonon-invasivelyidentifywoods used in some antique marquetry furniture and small carvings throughtheuseofreflectedlightmicroscopy.Limitsand poten-tialofreflectedlightmicroscopyasanon-invasiveidentification tool,i.e.withoutanypriorpreparationofobservedsurfaces,are hencediscussed,togetherwiththeroleofretrievedinformation forobjects’interpretation.

2. Introduction

Theknowledgeofthetimber(s)usedinawoodenobjectorwork ofartbelongingtotheculturalheritageisabasicinformationfor anystudy,conservationorrestorationactivity.Itsimportancecan varyfromonekindofartifacttoanother,butitisalwaysan essen-tialinformation.Theroleoftheknowledgeofthewoodsusedinan objectofart,inthespeciﬁccaseancientfurniture,isﬁnelypointed outinreference[1],wheretheauthorstates“_._._{.furniture-making}

∗ Correspondingauthor.Tel.:+00390116705540;fax:+00390116705556. E-mailaddresses:flavio.ruffinatto@unito.it(F.Ruffinatto),

corrado.cremonini@unito.it(C.Cremonini),macchioni@ivalsa.cnr.it(N.Macchioni), roberto.zanuttini@unito.it(R.Zanuttini).

1_Tel:₊₀₀₃₉_0116705542;_fax:₊₀₀₃₉_0116705556. 2_Tel.:₊₀₀₃₉_0555225502;_fax:₊₀₀₃₉_05552255070. 3_Tel.:₊₀₀₃₉_0116705541;_fax:₊₀₀₃₉_0116705556.

isessentiallyamanufacturingactivity,althoughitmayalsoinvolve artisticexpression,and,likeallmanufacturingprocesses,it there-forebeginswithrawmaterials”andmoreprecisely“knowledge ofthewoodsusedinfurniture-makingisnotjust aquestionof connoisseurship;itisafundamentalrequirementfor understand-inganypieceoffurniture”.Justtomentionfewotherexamples, withoutthisknowledgeitisimpossibleforinstancetoinferthe mechanicalstrengthofthetimberelementsinawoodenstructure

[2],whileinthearcheologicalstudies,allthephysicalandchemical measuredparametersarecomparedtothoseofthesoundwoodof thesametimberinordertodeterminetheamountofdecay[3].

Thequestiontherefore is:how canwe identifywoodonan antique?Rarelyidentificationthroughmacroscopicfeaturescan bereliable;inmostcasesmicroscopicanalysisisnecessary.Limits ofmicroscopicwoodidentificationhavebeenexaminedbymany authors,bothconsideringthetechniqueitself[4],andinrelation withspecificproblemsassociatedwithvaluableculturalartefacts

[5,6]. TheItalian standard UNI 11118[7] describescriteria and

limitsofspeciesidentiﬁcationonwoodenartefactsofhistorical, artisticandarchaeologicalinterest.Thisdocumentstatesthatthe identiﬁcationprocessisastep-by-steppath,whichstartsfromthe macroscopicobservationanddeepensuntilasatisfactorylevelof taxoncanbereached.Becauseoftheabovementionedlimits,even microscopicanalysiscandisappointexpectations.

Thesamestandardalsoindicatesthatsamplingisalways sub-jecttoanofﬁcialpermissionfromtheartefact’scurator,whoisthe soletohaveauthorityonthesubject.Suchauthorizationcanbe difﬁculttoobtainwhenartisticobjects,suchasstatuesandpanel 1296-2074/$–seefrontmatter©2013ElsevierMassonSAS.Allrightsreserved.

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paintings,areinvolved,evenifsamplingisalwaystargetedon hid-denplaces,likethebackoftheartifacts,ornon-decoratedparts

[8].Ontheotherhand,samplingcanbesometimesimpracticable, likeonpiecesofartwherethedecoratedorartisticfunctionsare givenbythewoodsurfaceitself.Thisisthecaseofmarquetryor preciouslydecoratedfurniture.

Thereforenon-invasivewoodidentiﬁcationcanbehighly pre-ferred,whennotunavoidable.

Reﬂectedlightmicroscopy(RLM)potentialasanon-invasive identiﬁcationtoolforwoodenculturalartefactshasbeendiscussed inarecentpaper[9].Herewetestthetechniqueandmethodology onhistoricalobjectsmadeavailablebythe“CentreofConservation andRestoringofLaVenariaReale”nearTurin,Italy.

Theguidingprincipleinartefactselectionwastogobackover theproductionofthecabinet-makerswhoalternatedattheservice oftheRoyalHouseofSavoiainPiedmontthroughtheXVIIIth_and

XIXth_Century._Following_this_path,_the_paper_takes_its_cues_from_a

rangeofdifferentmanufacturingtypologiestopresenttheresults obtainedthrough non-invasiveRLMand discusstheirreliability anddiagnosticvalue.

3. Materialsandmethods 3.1. Microscopes

Threedifferentreflectedlightmicroscopeswerealternatively useddependingonartefactsdimension:forthesmallestobjectsor partsanOlympusBX51opticalmicroscopefittedwithanOlympus TH4-200reflectedlightsource,apolarizingfilter(Pf),anOlympus U-MNB2narrow-bandbluefilter(Bf)andanOlympusDP71digital colorcamera;formediumsizedobjectsanOlympusSZX10 stere-omicroscopefittedwithanOlympusKL1500LCDlightsourceand aColorViewIdigitalcolorcamera;biggerobjectswhichcouldnot fitunderanyofthepreviousinstrumentswhereobservedwitha ScalarDG-3portabledigitalmicroscopeequippedwith25×–200× parfocalzoomlens.Asregardsfixedinstruments,adigitizedimage analysissystem(analySIS®,Olympus)wasusedfor microphotog-raphyandquantitativeanatomy.

3.2. Identiﬁcation

Allpieceswereobservedrigorouslyastheyare,avoidingany kindofsurfacealteration.Eachvisiblefeaturewasrecordedand documentedthroughphotographs,someexamplesofwhichare presentedinthepaper.Becauseofthereducedfeaturesvisibility entailedintheobservationofnon-preparedsurfaces(i.e.neither orientednorsurfaced),absenceofspeciﬁcfeatureswasnotused foridentiﬁcation.

TerminologyandsurveyprinciplesgenerallyfollowedtheIAWA listofmicroscopicfeaturesforhardwoodidentification[10]andthe IAWAlistofmicroscopicfeaturesforsoftwoodidentification[11]. Someexceptions,pointedoutinthetext,havebeenoccasionally madeasregardssurveyprinciplesinordertoadapt tosurfaces availability.Somecharacterstatesnot detailedintheIAWA list wererecordedtoo.Non-anatomicalfeatureswereoccasionally con-sideredsincetheyhavebeenprovedusefulinwoodidentification

[12],yetkeepinginmindthatsomeofthem,suchascolor,canbe easilymodiﬁedbytime,lightorhumanmanipulation,whichare allcommonagentsonancientartefacts.

Thereferences[13–20]wereadoptedforidentiﬁcation,while thereferences[1,21,22]wereconsultedforthebotanicalidentity ofcommonnames.Referenceinformationaboutemployedwoods, whenavailable,wereusedforthesolepurposeofresults compari-sonanddiscussion.

3.3. Artefacts

Secretary chest of drawers with shelves, Decorative arts museumofthe“PietroAccorsi”Foundation,Turin–PietroPiffetti (1701–1777).

Thisartpieceisalmostthetwinoftheoneconservedatthe QuirinalePalace(ofﬁcialresidenceofthePresidentoftheItalian Republic).Bytraditionthemainveneer(Fig.1a)wassupposedtobe “rosewood”.Unfortunately,thebotanicalidentityofthisvernacular namecan’tberetrieved,sinceit hasbeenwidelyusedover the centuriesforwoodsbelongingtoseveraldifferenttaxa[1].Alittle looseveneercard,whichhadtoberearrangedbyrestorers,was observedonbothsidesbymeansoftheOlympusBX51.

Centretable,PalazzinadiCacciadiStupinigi–GiovanniGalletti (XVIIIth_century).

Themainveneer(Fig.2)consistsofacompositionoftransverse sectionsandwoodburls,aquiteoriginalpatternforthistypeof objects.Inanancientdocumentreportedby[23]itwasattributed to“busso”,anItalianvernacularnameforboxwood(Buxus sem-pervirens)[21].Observationsaimedtoverifythisassumptionwere performedonthedrawersinbothsidesofthetablebymeansof theScalarDG-3.

Table,PalazzinadiCacciadiStupinigi–GiovanniGalletti (spec-ulation).

Twoveneers(Fig.3aandb)lackinganydocumentalinformation wereobservedbymeansoftheScalarDG-3.

CarloXtable,ReggiadiValcasotto,Garessio–GabrieleCapello (1806–1877,speculation).

Anydocumentalinformationaboutthespeciesusedislacking. Based ongeneralhistoricalknowledge,thelight-coloredveneer (Fig.4a)wassupposedtobe“citronnier”or“satinwood”,towhich speciesfromdifferentgeneracanbereferred,mainly:Chloroxylon, Morus,Pericopsis,Zanthoxylum[1,22,24].Thedarkinlay(Fig.4b) wassupposedtobe“purpleheart”,i.e.,Peltogynesp.[1]and[22]. BothwereanalyzedbymeansoftheScalarDG-3.

Militarytrophy,PalazzoMadama,Turin–GiuseppeMaria Bon-zanigo(1745–1820).

Bonzanigo,apartfrombeingagreatcabinet-maker,is world-wide recognized as one of the most prominent wood carvers, especiallyregardingminiature.Thisworkofartisanexampleof hisoutstandingskillsand,beingmadeupofseveralsmallpieces, constitutesanexceptionalchanceforstudy.Vernacularnamesof sometimbersusedin thisart piececanbefoundinanancient documentmentionedin[25].Theauthorstatestohavecollected theseinformationdirectlyfromtheartist,butdoesnotspecifyany correspondencetosinglepieces.

Somepieces(Fig.5–10),representativeofdifferenttypologies insidetheartifact,wereanalyzed.Thankstotheirlimited dimen-sions, theycouldbeobservedwiththe OlympusBX51, but the OlympusSZX10wassometimesusedtoo.

4. Resultsanddiscussion

For abettercomprehensionresultsare displayedinTable1; hereinafteridentiﬁcationresultsarediscussed.

Both tropical (Dalbergia, Pterocarpus) and Italian indigenous (Buxus,Laburnum,Taxus)generawereidentiﬁedonfurniture,while inonecaseanidentiﬁcationcouldnotbeprovided.

Dalbergiacomprisesapproximately250species[26]distributed fromthetropicaltosubtropicalregionsoftheWorld[16,27],some ofwhichcanbenumberedamongthemostwantedwoodsfor valu-ablefurniture[1,24].Althoughonlyaround10–15speciesareof economicimportance[28],separationofsomeofthemis nowa-daysachallenge[29].Severalspeciesofthegenushavebeentraded (andstilltheyare)underthename“rosewood”[1],thesupposed

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Table1

Observedsurfaces,charactersandidentificationofeachobservedpiece.Surfacesarereportedwithdetailsaboutorientation,evenness,extensionandfinishing;characters withdetailsaboutIAWAcodesinbracketsforlistedfeatures,filters(ifused),surfaceofsurvey(ifdifferentfromsurveyprinciples)andmagnificationtowhichtheyhave beenobserved;whenanItalianindigenousgenusisidentified,localspeciesaresuggestedinbrackets.

Artefact Piece Observedsurfaces Characters Identiﬁcation

Secretarychestof drawerswith shelves

– Tangential,notperfectly

orientated

Finishedwithshellacon thefrontside,withglue tracesontheback Allfeaturesweredetected ontheshellacﬁnishedside exceptthan“52”

Intervesselpitsalternate(22;Bf;500×) Intervesselpitsmedium(26;Bf;500×) Vesturedpits(29;Bf;500×)

Meanvesselelementlength≤350␮m(52;Pf;100×) Eight(5-8)cellsperparenchymastrand(93;Bf;200×;

Fig.11)

Allraysstoried(118;Bf;100×)

Heartwoodbasicallybrownorshadesofbrown(197) Heartwoodwithstreaks(201)

Hardwood:Dalbergiasp.

Centretable – Transverse,radialand tangential.Finishedwith shellac

Bodyraycellsprocumbentwithonerowofuprightand/or squaremarginalcells(106;100×)

Bodyraycellsprocumbentwithmostly2-4rowsof uprightand/orsquaremarginalcells(107;100×;Fig.12) Heartwoodbasicallyyelloworshadesofyellow(199)

Hardwood:probablyBuxussp. (Buxussempervirens)

Table Veneer“a” Tangentialandradial. Finishedwithshellac

Woodring-porous(3;radialsurface;40×)

Vesselsintangentialbands(6;latewoodvesselsjagged patternvisibleontangentialsurface;40×)

Fusiformparenchymacells(90;100×;Fig.13)

Largerrayscommonly4-to10-seriate(98;100×;Fig.13) Bodyraycellsprocumbentwithonerowofuprightand/or squaremarginalcells(106;100×)

Sheathcells(110;100)

Heartwoodcolordarkerthansapwood(196)

Hardwood:Laburnum anagyroides

Veneer“b” Tangentialandradial. Finishedwithshellac

Heartwoodcolorbrownorshadesofbrown(26) Growthringboundariesdistinct(40;radialsurface;100×; Fig.14)

Transitionfromearlywoodtolatewoodgradual(43;radial surface;100×;Fig.14)

Helicalthickeningsinlongitudinaltracheidspresent(61; 100×;Fig.14,poorlyvisible)

Averagerayheightmedium(103;100×) Raysexclusivelyuniseriate(107;100×)

Softwood:probablyTaxussp. (Taxusbaccata)

CarloXtable Veneer“a” Radialandtangential; transversesurfacenot perfectlyorientatedandof limitedsize

Finishedwithshellac

Growthringboundariesdistinct(1;40×) Wooddiffuse-porous(5;40×)

Meantangentialdiameterofvessellumina100–200␮m (42;100×)

Septateﬁbrespresent(65;100×)

Largerrayscommonly4-to10-seriate(98;100×;Fig.15) Allraycellsprocumbent(104;100×)

Heartwoodbasicallyyelloworshadesofyellow(199)

Hardwood:uncertain

Inlay“b” Tangential.Finishedwith shellac

Meantangentialdiameterofvessellumina≥200␮m(43; 100×)

Meanvesselelementlength≤350␮m(52;100×) Raysexclusivelyuniseriate(96;100×;Fig.16); Allraysstoried(118;100×;Fig.16); Heartwoodwithstreaks(201)

Hardwood:Pterocarpussp.

Militarytrophy Piece“5” Uneventangentialand smallradialandtransverse surfaces

Finishingabsent

Wooddiffuse-porous(5;50×) Simpleperforationplates(13;Pf;100×)

Helicalthickeningsinvesselelementspresent(36;200×; Fig.17)

Largerrayscommonly4-to10-seriate(98;200×;Fig.17) Raysoftwodistinctsizes(103;200×)

Allraycellsprocumbent(104;Bf;200×)

Axialparenchymaabundant(tangentialsurface;100×)

Hardwood:probablyTiliasp. (TiliacordataorTilia platyphyllos)

Piece“6” Uneventangential, transversesurfaceof limitedsize Finishingabsent

Wooddiffuse-porous(5;50×)

Vesselsindiagonaland/orradialpattern(7;50×); Helicalthickeningsinvesselelementspresent(36;500×) Fibrepitscommoninbothradialandtangentialwalls(63; Pf;500×)

Helicalthickeningsingroundtissueﬁbres(64;500×; Fig.18)

Largerrayscommonly4-to10-seriate(98;200×); Rayheight>1mm(102;Pf;100×)

Raysoftwodistinctsizes(103;Bf;200×) Sheathcells(110;200×);

Uniseriateraymargins(tangentialsurface;200×)

Hardwood:Ilexsp. (Ilexaquifolium)

Piece“7” Uneventangentialand smallradialsurface Finishingabsent

Simpleperforationplates(13;126×)

Meantangentialdiameterofvessellumina≤50␮m(40; tangentialsurface;126×)

Raywidth1to3cells(97;200×;Fig.19) Allraycellsprocumbent(104;126×)

Heartwoodbasicallybrownorshadesofbrown(197)

Hardwood:Pyrussp.,Sorbussp. orMalussp.

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Table1(Continued)

Artefact Piece Observedsurfaces Characters Identiﬁcation

Piece“8,a” Uneventangentialand smalltransversesurface Finishingabsent

Wooddiffuse-porous(5;50×;Fig.20)

Helicalthickeningsinvesselelementspresent(36;200×) Meantangentialdiameterofvessellumina≤50␮m(40; 50×;Fig.20)

Raysexclusivelyuniseriate(96;Bf;200×);

Vesselssolitaryorinshortradialrows(transversesurface; 50×;Fig.20)

Hardwood:Aesculussp. (Aesculushippocastanum)

Piece“8,b” Unevenradialandsmall tangentialandtransverse surfaces

Finishingabsent

Scalariformperforationplates(14;500×;Fig.21,onlybar residualsvisible)

Meantangentialdiameterofvessellumina≤50␮m(40; 50×)

Fibreswithdistinctlyborderedpits(62;Bf;500×) Raywidth1to3cells(97;Bf;500×)

Bodyraycellsprocumbentwithonetofourrowsof uprightand/orsquaremarginalcells(106&107;Bf;200×) Vesselluminameantangentialdiameter≈20␮m (transversesurface;50×)

Hardwood:probablyBuxussp. (Buxussempervirens)

Piece“9” Unevenradialandsmall tangentialandtransverse surfaces

Finishingabsent

Simpleperforationplates(13;200×;Fig.22)

Helicalthickeningsinvesselelementspresent(36;200×; Fig.22)

Meantangentialdiameterofvessellumina≤50␮m(40; 50×)

Meanvesselelementlength350–800␮m(53;200×) Raysexclusivelyuniseriate(96;126×)

Vesselssolitaryorinshortradialrows(transversesurface; 50×)

Hardwood:Aesculussp. (Aesculushippocastanum)

Piece“10” Extremelyunevenradial andtransverse. Finishingabsent

Growthringboundariesdistinct(1;Bf;100×;Fig.23) Wooddiffuse-porous(5;Bf;100×;Fig.23) Simpleperforationplates(13;100×)

Meantangentialdiameterofvessellumina50–100␮m (41;Bf;100×;Fig.23)

Raysexclusivelyuniseriate(96;Bf;transversesurface; 100×;Fig.23)

Hardwood:Populussp. (Populusalba,Populusnigra, Populustremula)

Figs.1–4.Artefactsdetails.1.PietroPiffetti;Secretarychestofdrawerswithshelves,Decorativeartsmuseumofthe“PietroAccorsi”Foundation,Turin.2.GiovanniGalletti; Centretable,PalazzinadiCacciadiStupinigi.3.GiovanniGalletti;Table,PalazzinadiCacciadiStupinigi.4.GabrieleCapello;CarloXtable,ReggiadiValcasotto,Garessio.

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Figs.5–10.Artefactsdetails.GiuseppeMariaBonzanigo;Militarytrophy,PalazzoMadama,Turin.Scalebars=1cm.

Figs.11–14. Identiﬁedcharacters;blueﬁlterwhenused(Bf)andIAWAcodes(forlistedfeatures)reportedinbrackets.11.(Bf):eight(5-8)cellsperparenchymastrand(93). 12.Bodyraycellsprocumbentwithmostly2–4rowsofuprightand/orsquaremarginalcells(107).13.Fusiformparenchymacells(90);largerrayscommonly4-to10-seriate (98).14.Growthringboundariesdistinct(40);transitionfromearlywoodtolatewoodgradual(43);helicalthickeningsinlongitudinaltracheidspresent(61).–Scalebars: 11=50␮m;12–14=150␮m.–Microscopes:11:OlympusBX51;12–14:ScalarDG-3.

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Figs.15–23. Identifiedcharacters;bluefilterwhenused(Bf)andIAWAcodes(forlistedfeatures)reportedinbrackets.15.Largerrayscommonly4-to10-seriate(98).16.Rays exclusivelyuniseriate(96);allraysstoried(118).17.Helicalthickeningsinvesselelementspresent(36);largerrayscommonly4-to10-seriate(98).18.Helicalthickeningsin groundtissuefibres(64).19.Raywidth1to3cells(97).20:wooddiffuse-porous(5);meantangentialdiameterofvessellumina≤50␮m(40);vesselsolitaryorinshortradial rows.21.Scalariformperforationplates(14).22.Simpleperforationplates(13);helicalthickeningsinvesselelementspresent(36).23.(Bf):growthringboundariesdistinct (1);wooddiffuse-porous(5);meantangentialdiameterofvessellumina50-100␮m(41);raysexclusivelyuniseriate(96).Scalebars:17,19,22,23=50␮m;15–16=150␮m; 18=25␮m;20=250␮m;21=10␮m.Microscopes:17–19,21–23:OlympusBX51;15–16:ScalarDG-3;20:OlympusSZX10.

attributionforthisveneer.Noteworthyisthebettervisibilityof mostfeatures,reallysmallonessuchasintervesselpitsdimension andvesturingincluded,ontheshellacfinishedsideoftheveneer cardratherthanthenon-finishedone;thusconfirmingthe posi-tiveeffectofshellaconanatomicalfeaturesvisibilitypointedoutin

[9].ThePterocarpusgenusincludesextremelyvaluabletimberstoo, whichhavebeenextensivelyusedinmarquetryfurniture[1,24]. Theidentificationdoesnotconfirmtheinitialassumption (Peltog-yne).Laburnumanagyroides,goldenchain,hasbeenoftenemployed inmarquetryasasubstituteformoreexpensiveexoticones,such asmahogany[1,24].BuxusandTaxusidentificationsarenot cer-tain.Asforthefirst,althoughobservedfeaturesareinagreement withdocumentedinformation,nosufficientanatomical informa-tionweredetectedtoconfirmthegenus.Inparticular,perforation platetypeevidenceisneeded,becauseBuxushasexclusively scalar-iformperforations.Thedifficultymetinidentifyingthisfeatureis notsurprisingifwelookatitscomparativelylowFeature Recog-nitionIndexonnon-finishedsurfacespointedoutinreference[9]. Moreover,itmustbenotedthattheindistinctnessofnumerous individualcharacterstatesisduetotheextremelyfinetextureand grainofthewood,whichisinagreementwithanidentityofBuxus wood,alsoveryfine-grained.Asregardsthesecond,moreclear

evidenceofhelicalthickeningsshouldbeneededforconfirmation. Yewwood,mostlyknownforitsuseinlongbowsmanufacturing sincemedievaltimesinEngland[1],wasfrequentlyusedin mar-quetryinordertoemulateexoticones[24].InthecaseoftheCarlo Xtable“veneera”,observedfeatureswerenotsufficienttomake anaccurateidentification,butstillallowedtoexcludeanyofthe generacommonlyknownas“citronnier”or“satinwood”.

Allthewoodsidentiﬁedonthemilitarytrophysculpturesbelong toItalianindigenousgenera.Halfofthemarenotmentionedin[25]: Tilia,IlexandtheRosaceaegroup(Pyrus/Malus/Sorbus);while Aes-culus,BuxusandPopuluscanberetrievedinthedocumentwiththeir correspondentvernacularnames,respectively“castagnod’India” (literally“Indianchestnut”),“bosso”and“pioppomaschio(literally “malepoplar”).

Thewoodofholly(Ilex)isreportedtobevaluedasacarving materialespeciallybecauseofitscolorresemblancetoivoryand ﬁnetexture[24].Atthisregard,noteworthyisthepresenceinthe centreofthetrophyofasimilarportraitmadeofivoryrepresenting thekingVittorio EmanueleI,towhom theobjectwasdonated

[30].Thiscouldsuggestaninterestingartisticchoice,nowadays hiddenbydiscolorationofthewood.AesculusandPoplarwoods tooaretraditionallywidelyusedforcarving[24].BuxusandTilia

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identificationsarenotcertain.Inthefirstcase,evidenceofintact scalariformperforationplatesisneededforfurtherconfirmation. Because of wood discoloration this piece shows no more any evidentcolorcontrastwithitssupport(Fig.8a)madeofAesculus, whichinsteadwasprobablytheoriginalintentionoftheartist.The useofboxwoodforcarving,especially forsmallrefinedobjects, can be traced back to ancient times [24]. In the second case, evidenceofaxialparenchymapatternwouldbeusefulforfurther confirmation.Limewoodisamongstthepreferredtimbersallover Europeforcarving[24].Finally,onthebasisofobservedfeatures furtherdiscriminationwasnotpossibleamongstthethreegenera Pyrus,Sorbus,MalusbelongingtotheRosaceaegroup,allwoods highlyvaluedforrefinedcarvingandturning[24].

5. Conclusions

Conventionallywood anatomical identification is performed throughtheanalysisofeachoneofthethreeplanesofobservation ofwood(transverse,longitudinalradial,longitudinaltangential). In most of the examined cases all the three planes were not availablesimultaneously and atleast one ofthe availableones wasnotclearlyvisiblebecauseofsurfacesize,orientation, even-nessorfinishing.Ofthethree,thecrosssection(veryimportant, especiallyfor hardwoodsidentification) wasthelessfrequently observable.

Nevertheless,inspiteofalltheselimitations,sevenoutofthe13 investigatedpieces(Fig.1a,3a,4b,6,8a,9and10)wereidentiﬁed withthehighestaccuracyreachablethroughanatomicalanalysis. Forothersixpieces,ahypothesiscouldbeprovidedtogetherwith thedetailaboutlackingfeaturesneededforconﬁrmation.Inthe worstcase,(Fig.4a)theexclusionofapreviousspeculationcould besupportedanyway.

Amongstthethreetestedinstruments,theopticalmicroscope providedbyfarthebestperformances,duetohighermagniﬁcation andtheavailabilityofpolarizationandﬁlters(whicheffectiveness waspointedoutin[9]too).Stereomicroscopesandportable dig-italmicroscopeswerehelpfulforbiggerobjects,whichcouldnot beobservedattheopticalone,butfeaturesvisibilitywasnotas good.

Ourstudyconfirms that RLMcan beconsideredaneffective toolfornon-invasivewoodidentification.Inseveralcasesableto supportaccurateidentification,in othersitcananywayprovide importantinformation,usefultoexcludesupposed speciesorto limittheinvasivenessofpossiblefurtheranalysisbyaddressing themonspecificfeatures.

Acknowledgments

The“CentreofConservationandRestoringofLaVenariaReale” isacknowledgedforprovidedartefacts;specialthankstoMassimo Raveraofthe“WoodenobjectsRestoringLaboratory”for interest-ingdiscussionandtothe“PhotoLaboratory”forinitialartefacts images.Financial supportwasprovided bythe“Fondazioneper l’ArtedellaCompagniadiSanPaolo”.

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