Nondestructive on-site identification of ancient glasses: genuine artefacts, embellished pieces or forgeries?

A selection of 23 rare glass objects, mostly enameled, of various provenance and age, from the 5th century BC to the 19th century AD including the Western and Islamic Middle Ages but with a focus on 16th-18th century Venetian and French' facon de Venise' artefacts, have been studied on-site at the Sevres museum or at the laboratory. The Raman signatures of the transparent or opacified glass matrix and of enameled decorations are discussed and compared to those previously recorded on ceramics and stained glasses. The Raman parameters allow discrimination between 2 groups (with some variations) of glass bodies, belonging to mixed Ca-Na and Ca-containing Na-rich silicates, with some exceptions. Most enamels are instead lead-based glasses, but we also found enamels having a composition close to that of the glass body. Most of the pigment signatures are similar to those recorded on ceramic glazes, which proves the link between the two technologies. A particular emphasis was given to the identification of white opacification techniques. Very specific signatures could question the authenticity of some artefacts, and at least in two cases, arguments have been found to identify a fake or embellished artefact. Copyright (C) 2008 John Wiley & Sons, Ltd.