Concerning the archeological samples, the spectra adjustments
are different between the internal part and the altered surface
part. In a general way, for the external samples, the bands get
broader (W is higher for the surface samples), their profile tends
towards a Gaussian one; and some bands' intensity decreases
significantly. Band number 10 almost disappears for some arche-
ological copals (the red ones). It is related to CH bonds in vinyl
groups which may be transformed (oxidized) during alteration
processes [41].