Non-Invasive On-Site Raman Study of Pigments and Glassy Matrix of 17th-18th Century Painted Enamelled Chinese Metal Wares: Comparison with French Enamelling Technology

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 cloisonne and/or painted enamels and belong to the collections of Musee du Louvre in Paris and Musee 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 cloisonne 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 degrees nanoparticles) in red to violet enamelled and cloisonne 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.