Raman spectroscopic studies of a 13th century polychrome statue: identification of a ?forgotten? pigment

Abstract

A Raman microscopic analysis of pigments applied to a 13th century polychrome stone statue of Santa Ana in Santa Maria la Real, Sasamon, Spain, has successfully identified the materials used. The spectral analysis reveals that the stone substrate had been treated with gypsum prior to the application of the pigments. The use of cinnabar, mercury(II) sulfide, in admixture with lead(II) lead(IV) oxide (minium), is a feature of interest; the presence of calcite in the cinnabar could point to a local mineralogical source. The presence of organic compounds in the pigments analysed suggests their use as binding agents or surface varnishes for protection or enhancement of the appearance of the statue. The use of ‘mosaic gold’, tin(IV) sulfide, in place of gold on the hem of the cape, identified by Raman spectroscopy and confirmed by SEM points to the use of a forgotten technology. Our results also suggest a spectroscopic protocol for the identification of tin(IV) sulfide in ancient pigment mixtures in the presence of other sulfide pigments such as orpiment, realgar and cinnabar. Copyright © 2000 John Wiley & Sons, Ltd.