If weaddaninternalpartofanarcheologicalcopalto
this graph,itgetsplacedintheverybeginningofthearrow.
This axiscanthusbeconsideredasanalterationindextoqualify
the degradationstateofeachsample,withtheinternalsampleas
a reference(unaltered)point.Indeed,alltheyellowcopalsarein
the first halfontheaxisandtheredonesonitssecondpart.The
first assumptionthatthesamplescolorisrelatedtothealteration
degree isheresatisfied. Moregenerally,screeningalargercorpus
of samples,whethernaturallyalteredorartificiallyaged,canlead
toamorecompletecalibrationtoolwhichcanbeusefulforthe
diagnostic oftheconservationstateofawiderangeofnatural
organic substances.Moreover,thedifferenceinthecopalssurface
aspect caninformaboutthetransformationstheymighthave