A noninvasive complementary study of an Egyptian polychrome cartonnage pigments using SEM, EPMA, and Raman spectroscopy

Abstract

Raman spectroscopy, optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) were used to study pigments on an Egyptian cartonnage from the Ptolemaic period (305–30 BC). The surface morphology of each color region was examined using backscattering (BS) and secondary electron imaging. SEM X-ray energy dispersive spectrometry and EPMA wavelength dispersive spectroscopy provided semiquantitative chemical analysis of each pigment. Raman spectroscopy was used to identify the minerals associated with the pigments. This technique confirmed the presence of cinnabar (α-HgS) in the red part of the fragments. A mixture of orpiment (As2S3) and bonazziite (β-As4S4) and/or alacránite (As8S9) was detected in the yellow regions of the fragments. The orange pigment was confirmed to be a mixture of orpiment, uzonite (χ-As4S5), and pararealgar (As4S4). Egyptian blue (CaCuSi4O10) and Egyptian green ((Cu,Ca)SiO3) pigments were detected from blue/green dark-colored regions of the fragments.