Fabrication processes of archaeological Egyptian blue and green pigments enlightened by Raman microscopy and scanning electron microscopy

Abstract

The preparation process of Egyptian blue and green pigments was studied by using scanning electron microscopy and Raman microscopy on archaeological samples. Together they allow the identification of the molecular or crystalline structure of different areas each characterized by their elementary composition or morphology. The main result is the identification of tenorite (CuO), which proves that the syntheses of both compounds were performed in an oxidizing atmosphere. The siliceous areas are always α-quartz; in green pigments, α-cristobalite is rarely observed. In addition, a reference Raman spectrum of cuprorivaïte (CaCuSi4O10), the blue crystalline compound of Egyptian blue, was obtained. Copyright © 1999 John Wiley & Sons, Ltd.