The Effect of Excimer Laser Irradiation on Historical Pigments

The use of alternative methods of cleaning easel paintings that mitigate the possible problems of irreversible changes to the pigment/binder matrix caused by solvent-based methods is an active area of research. Laser ablation is used as a viable cleaning method for the conservation of stone, but its application to paintings still requires further study. The objective of this research is to advance the understanding of the effects that KrF excimer laser irradiation has on pigmented layers. A comparative study of laser cleaning of samples of pure pigment and pigment mixtures used in the 19th century was carried out, and their response to different laser parameters is reported. Analytical characterisation was performed by colourimetry, optical microscopy, SEM, FTIR and Raman spectroscopy. The study concludes that pigments have different sensitivities to 248 nm irradiation; this also alters the degradation of the oil media. It has been demonstrated that the effect of the irradiation on a pigment mixture cannot be predicted from the effect of the individual pigments; and that the processes occurring in mixtures require further research