Multianalytical approach to the analysis of English polychromed alabaster sculptures: muRaman, muEDXRF, and FTIR spectroscopies.

Abstract

A complete study of several English polychromed alabaster sculptures is presented. The support, pigment, and binders were characterised by combining muEDXRF, muRaman, and FTIR spectroscopies. Among the pigments, minium, vermilion, lead white, carbon black, red iron oxide, and a degraded green copper pigment were determined, together with gold leaf. The presence of the rare mineral moolooite (copper oxalate) was also found as a degradation product in the green areas, where weddellite (calcium oxalate dihydrate) was also determined. These facts, together with degradation of the green copper pigment, suggest microbiological degradation of the original materials. Remains of glue and a varnish were also determined by FTIR spectroscopy and principal-components analysis (PCA) of the spectra. Finally, PCA analysis was carried out to confirm whether the pieces came from the same quarry.