Abstract
A selection of 10 Chinese enamelled metal wares dating from the 17th–18th centuries (Qing Dynasty) was analysed on-site by mobile Raman microspectroscopy. These wares display cloisonné and/or painted enamels and belong to the collections of Musée du Louvre in Paris and Musée Chinois at the Fontainebleau Castle in France. Pigments (Naples yellow lead pyrochlore, hematite, manganese oxide etc.), opacifiers (fluorite, lead arsenates) and corresponding lead-based glassy matrices were identified. One artefact was also analysed by portable X-ray fluorescence spectrometry (pXRF) in order to confirm the Raman data. In some of these metal wares, it is suggested that cassiterite was unpredictably used as an opacifier in some parts of the decor. The results are compared to previous data obtained on Chinese cloisonné and Limoges enamels as well as recent data recorded on painted enamelled porcelains of the Qing Dynasty. Lead arsenate apatite detected in some of the 17th–18th century blue enamelled decors is related to the use of arsenic-rich European cobalt ores, as also characterized in French soft-paste porcelain and glass decors and high-quality Limoges enamels for the same period. However, lead arsenate could then also have been deliberately used for white opacification. The specific Raman signature displaying the shape of the Raman scattering background indicates the presence of colloidal gold (Au° nanoparticles) in red to violet enamelled and cloisonné areas. At least three types of Naples yellow lead pyrochlore pigments identified with Sb-rich, Sn-rich and mixed Sb–Sn–(Zn, Fe?) compositions prove the use of European pigments/recipes.
Highlights
An enamel can be defined as a glassy material, made by mixing various types of fluxes and colouring/opacifying agents with silica, which is discretely applied and fused onto several bases upon subsequent firing in order to get a glossy coating [1,2]
We present the first non-invasive on-site study of 10 enamelled metal wares dating to the 17th–18th centuries (Qing Dynasty) from the collections of Musée du Louvre (Département des Objets d’art, Paris) and Chateau de Fontainebleau (Musée Chinois, Fontainebleau) by mobile Raman microspectroscopy
The objective of this study is the comparison of the enamelling technology used in these artefacts, regarding cloisonné and painted enamels, with the identification of pigments/opacifiers and glass types used
Summary
An enamel can be defined as a glassy material, made by mixing various types of fluxes and colouring/opacifying agents with silica, which is discretely applied and fused onto several bases upon subsequent firing in order to get a glossy coating [1,2]. [6] whereas the earliest examples of enamelled metal were found in Cyprus, Mycenaean Greece and China at about the same time period [3,7,8]. The earliest enamel applications were carried out onto gold and silver [8], such as in the golden cloisonné rings of Bronze Age Cyprus [7]. Several‘cultures including the Celts and Romans adopted the craft of enamelling on metal for producing more sophisticated decorations and correspondingly developed various techniques such as champlevé (the support is curved in order to make valleys in which the molten glass is retained) and cloisonné (pieces of metal foil set perpendicularly to the substrate are stuck in order to form walls that retain the molten glass according to the target design) [3,9,10].
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