Pigment Identification on a XIV/XV c. Wooden Crucifix Using Raman and LIBS Techniques

Abstract

The Raman and laser-induced breakdown spectroscopy (LIBS) techniques were applied for pigment identification in polychrome layers on a Polish 14th/15th-century wooden crucifix. In the Raman spectra, characteristic bands associated with compounds of the pigment samples taken from different areas of the object are observed. Groups of bands corresponding to the original white, red, and green pigments allow the identification of chalk, vermilion, red lead, malachite, and azurite. From the presence of bands ascribed to Prussian blue (282, 538 cm-1) and chrome yellow (338, 360, 403 cm-1), known since the 18th century, it can be concluded that some of the crucifix's elements have been retouched. The elemental composition is obtained from LIBS profiles recorded under excitation at 248 and 266 nm. The gold leaf technique is identified, and the presence of Cu, Pb, Cr, Fe, CN, C2, and Ca agrees with the pigment composition applied for retouching and observed in the Raman bands.