Colour changes in Galician granitic stones induced by UV Nd:YAG laser irradiation

Abstract

[Resumen]: estudio sobre el cambio de color del granito gallego al limpiarlo mediante láser ultravioleta

[Abstract] Laser cleaning has become a high profile and accepted specialized cleaning technique for most stone types. Given that local natural building stone in our region, Galicia (North West of Spain) is granite, our interest was focused on the response of this stone type to laser cleaning. The aim of this work is to determine the change in colour as index of the response of galician granites to UV-Nd:YAG laser exposure. For this purpose samples of commercial granites from different quarries were irradiated at increasing fluences. Colour changes were determined through the analysis of digital images and expressed in the L*a*b* and L*h*C* colour models. The results enable the establishment of application limits of laser cleaning to these materials