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

Abstract

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 'façon de Venise' artefacts, have been studied on-site at the Sèvres 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.

On-site Raman analysis of 17th and 18th century Limoges enamels: Implications on the European cobalt sources and the technological relationship between Limoges and Chinese enamels

“…Raman analyses showed that the opacification of the Limoges enamels studied was carried out with tin oxide (cassiterite, 635-775 cm -1 doublet [26,27]) for the white areas of all artefacts, as previously observed for similar and older items [9].The peaks are narrow and rather strong, indicating the use of a highly crystalline cassiterite. According to the previous study, another opacifying agent, namely lead arsenate, was also observed only in the 19 th century Limoges artefacts [9].…”

“…The white pigment (opacifier) has been described as made of tin oxide [22] but also as an arsenic-based compound [25]. Tin oxide had been in use as an opacifier since the 5 th century [26] and arsenic was first used in the making of lattimo glass in Murano during the 16 th century [27]. However, its common use as a glass opacifier was developed during the second half of the 19 th century [28].…”

The Use of Metal Nanoparticles to Produce Yellow, Red and Iridescent Colour, from Bronze Age to Present Times in Lustre Pottery and Glass: Solid State Chemistry, Spectroscopy and Nanostructure

“…Examples of lustre Fatimid glasses (a, original bottle; b, a fake [114]) and of red copper Krich glasses (b,c). The samples are from b) Aube French Country (13 th century) and c) from Amiens Cathedral (13 th to 17 th century), respectively [100].…”

“…The first preparation of ruby glass, is assigned to Bernard Perrot an Italian glassmaker working in Orléans ( [114] and references herein). Usually, gold nanoparticles are precipitated due to tin oxide from a gold solution in regal acid and then incorporated into the glaze precursor before firing [7].…”

Raman microscopy and x-ray fluorescence analysis of pigments on medieval and Renaissance Italian manuscript cuttings

“…Application of RM to the study of manuscripts, paintings, ceramics, glass, icons, and archaeological artifacts etc., permits the identification of most of the pigments present and many dyes, facilitating the establishment of artists' palettes at different periods and in different localities (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). It can also aid in the identification of previous restorations and in the detection of forgeries (18).…”