Raman studies of the underglaze blue pigment on ceramic artefacts of the Ming dynasty and of unknown origins

A micro-Raman spectroscopic study of underglaze blue ceramic shards was undertaken. The shards in this study are of Ming, Meissen and unknown origins. The Ming samples were donated to the National Cultural History Museum in Pretoria by private collectors and were confirmed by the museum as originating from the Ming period (1368-1644) in China. The shards of unknown origin were also supplied by the Museum and were excavated at sites in and around the city of Pretoria, South Africa. The shard obtained from the Museum fur Angewandte Kunst, Frankfurt am Main, originated from Meissen, close to Dresden in Germany and dates from the late 19th century. The blue pigment on all the shards was probed by focussing through the glaze at the ceramic/glaze interface using the depth-profiling method. The blue pigment used for decoration in all samples that were studied has been identified as the spinel-structured cobalt blue or cobalt aluminium oxide (CoAl2O4) and was shown to be mixed with amorphous carbon in two of the unknown archaeological shards, presumably to obtain a darker shade of blue. The unknown shards are also shown to contain white anatase (TiO2) applied on the surfaces prior to application of the colour and glaze, thereby suggesting the use of a two-step technology for the unknown archaeological shards as opposed to a single-step technology used by the Ming manufacturers. These differences could be used to distinguish shards of Ming origin from others. The method of probing the blue pigment through the glaze proved very useful and can now be extended to the study of underglaze pigments on the large number of intact glazed ceramic artefacts in museums around the world for comparison with archaeological shard samples. Copyright (C) 2007 John Wiley & Sons, Ltd.