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

Presentado en International Conference Lacona VII, Madrid, Spain, 17-21 September 2007[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 material

Compositional depth profiles of gilded wood polychromes by means of LIBS

[Resumen] Se analizan las diferentes capas existentes en retablos de maderas policromadas del periodo barroco. Se distinguen la capa base y las posteriores hasta el acabado mas superficial. Se aprecian las diferentes técnicas aplicadas en función de la procedencia y del autor que las ha realizado.[Abstract] Gilded wood polychromes are important artistic expressions in Galicia (NW Spain) during the baroque period. The variety of techniques applied in gilded ornamentation and the possible existence of products of previous interventions make difficult the restoration process of these artworks which frequently include the removal of a brass-based paint (purpurin) added to cover the lack of gold leaf. The aim of this work is the characterization by means of LIBS of the different layers in gilded wood polychromes. For this purpose small pieces taken from two baroque altarpieces were analyzed using a Nd:YAG laser source operating at the wavelength of 355 nm to obtain characteristic LIBS spectra and compositional depth profiles.Xunta de Galicia; PGIDIT06CCP00901C