Pigments analysis of an Egyptian cartonnage by means of XPS and Raman spectroscopy

Abstract

X-ray photoemission spectroscopy and Raman spectroscopy were used to identify pigments on an Egyptian cartonnage from the Ptolemaic period (305–30 BC). While XPS allowed us to perform a qualitative chemical analysis and establish the chemical composition of each pigment, Raman spectroscopy was employed to identify the associated minerals. High-resolution (HR) XPS spectra revealed the existence of Hg and S in the red region of the sample; Raman spectroscopy confirmed the presence of cinnabar (α-HgS), as the red pigment. Sulfur and arsenic were detected by HR XPS in the yellow part of the fragment, which is confirmed to be orpiment mineral (As2S3) by Raman spectroscopy. Raman spectra from blue/green dark-colored regions of the samples corresponds to Egyptian blue pigment (CaCuSi4O10). Detection of Cu and Cl by XPS, from the same region, is a strong indication of a degradation product of the Egyptian blue, namely a polymorph of trihydroxychloride Cu2(OH)3Cl.