A detailed micro‐Raman spectroscopic study of wall paintings of the period AD 100–200: effect of atmospheric conditions on the alteration of samples

Abstract

In this study, optical microscopy and micro-Raman spectroscopy were used to determine the chemical compositions of the materials used in the preparatory and pictorial layers of wall paintings from four different sites of the Roman Empire of first to second century AD. The use of UV excitation for the Raman work for the study of the preparatory layers made it possible to overcome the problems of fluorescence. The fresco technique, revealed by the presence of calcite in the Greek and Roman samples, was not used for the Gallo-Roman works. The studies indicated that the same compounds were used for red and green pigments throughout the Roman Empire: red ocher (hematite) and green earths (celadonite, in the case of the Gallo-Roman fragments). It is shown that the impact of the atmosphere on the sample surface is very important, because the only fragments to have suffered identifiable deterioration are those from the 'open-air humid room' in Kenchreai. The presence of gypsum in these samples in the absence of pigment indicates the implication of SO 2 in the deterioration and makes it possible to suggest that the pigments in the pictorial layer can serve as a protection for the calcite preparatory layers.

Recent advances in linear and nonlinear Raman spectroscopy. Part V

“…Cristini et al . used optical microscopy and micro‐Raman spectroscopy to determine the chemical compositions of the materials used in the preparatory and pictorial layers of wall paintings from four different sites of the Roman Empire of the 1st to 2nd century ad . The applicability of mobile, nondestructive techniques such as energy dispersive X‐ray fluorescence spectroscopy, which reveals the elemental composition, and fiber‐coupled Raman spectroscopy, offering molecular information, was applied by Deneckere and coworkers to the central panel of the Wyts triptych, after Jan van Eyck .…”

Raman microspectroscopic analysis of decorative pigments from the Roman villa of El Ruedo (Almedinilla, Spain)

“…Based on recent analyses of wall paintings, white pigments from Roman times consisted largely of carbonates [particularly calcium carbonate, CaCO 3 , in trigonal (calcite) or rhombic form (aragonite), in addition to mixed magnesium and calcium carbonates such as dolomite, CaMg(CO 3 ) 2 , or, less commonly, huntite, CaMg 3 (CO 3 ) 4 ]. Raman spectroscopy can accurately discriminate these compounds, so it has been widely used to examine white pigments of Roman origin [29][30][31]. Fig.…”

Raman spectroscopy of minerals and mineral pigments in archaeometry

“…Cristini et al studied the alterations of green earths from wall paintings in three different European sites (France, Rome and Greece) of the Roman Empire, dated in the 1st and 2nd centuries ad . Samples from mural paintings from archaeological sites from northeast of Italy were investigated by Moretto et al by a multitechnique approach, by comparison with celadonite and glauconite standards.…”