Comparative analysis of wucai Chinese porcelains using mobile and fixed Raman microspectrometers

Three porcelain shards representative of wucai (Famille verte, Famine rose and fencai), enamelled wares from Kiangxi, Yongzheng and Qianlong reigns have been studied using fixed instruments (optical microscope, EDS-SEM and Raman microspectrometer) in order to identify the amorphous and crystalline phases in the glaze, body and the different enamels. A comparison is made between the information collected with portable Raman set-ups excited with 532 and 785 nm lasers and equipped of sophisticated optics. Emphasis is put on the detection of pigments and opacifiers, in particular arsenic -based phases in blue coloured areas, in relation with the use of cobalt ores originated from European or China. The mobile Raman set-up excited with green laser and equipped with a high magnification (x200) ultra long working distance microscope objective allows the identification of all the phases, as for the fixed instrument excited with blue 457 nm laser line. Confirmation of the identified phases is made by SEM-EDS. The old technologies are discussed and compared to those used to produce 18th century French soft paste porcelains and Limoges enamels.