Spanish mediaeval frescoes at Basconcillos del Tozo: a Fourier transform Raman spectroscopic study

The late mediaeval frescoes in the Church of SS Cosmo and Damian at Basconc illos del Tote, Castille y Leon, Spain, were studied using Fourier transfor m Raman spectroscopy. The paintings were only discovered about 3 years ago and afforded a rare opportunity for spectroscopic analysis of pigments and substrata which have not been subjected to cleaning or re-touching over the last 600 years. Although in a polychrome palette, the most common pigments were reds, followed by black, yellow and blue; 20 samples were taken for a nalysis. The red pigments were identified spectroscopically and a hierarchi cal application is evident, with pure cinnabar being used for only the most important biblical figures. There is evidence in two of the samples taken of hydrated calcium oxalate, probably arising from lichen colonization, but it is not possible to infer whether this is pre- or post-mural painting. T he substrate shows no evidence for the presence of a gypsum plaster. The di fference between the red pigments in the paintings is associated spectrosco pically with mixtures of red ochre and cinnabar in the figures and also org anic coloured resins in the background. There is also some spectroscopic ev idence for the inclusion of red lead in figures in the lower panels. Copyri ght (C) 1999 John Wiley & Sons, Ltd.