Selected pictographs from the prehistoric painting panel 2 of Cueva del Tío Modesto shelter in the Sierra de las Cuerdas (Henarejos, Cuenca, Spain) were studied by Raman microscopy in order to determine the chemical composition of the pigments used. Hematite (α-Fe2O3) was found as the main component. The hematite particle size of one motif is much smaller than that observed for the others. No binders were found. A blue-greyish crust extends over the whole panel. Whewellite, weddellite and amorphous carbon were identified in this crust. The Triassic sandstone on which the paintings are made is found to suffer from a flaking process. Therefore, flakes of the rocky substratum were studied, and α-quartz, whewellite, magnetite and gypsum were found. A micro-stratigraphic study of the flakes revealed channels of gypsum from one side of the flake to the other. This result supports the mechanism proposed for this sandstone weathering process. Copyright © 2006 John Wiley & Sons, Ltd.