Another challengewastodetermineifthematerielalteration
has anyimpactonitsrecognition.Thearcheologicalcopalsare,in
this casealso,goodtestingsamplessincetheirsurfacepresents
more orlessalteration.OnthePCAscoreplot(Fig. 6) wecannotice
that thesurfacesamplesareinthesameclusterthantheinternal
samples, asfortheIRresults(supplementary Fig. 3s). Moreover,
othertransformedmaterials,forexamplelinseedandpoppyseed
oil films, areaswellintheoilsclusterwithaPC1of6andaPC2
around2(Fig. 6). Ageingoralterationdoesnotseem,toacertain
extent,hinderthematerialidentification.