Chemical Compositions of Co-Based Materials in Yuan Dynasty Blue-and-White Porcelains

The Chinese Yuan Dynasty blue-and-white porcelains exhibit different ornamentation effects, such as bow string and main patterns. In this study, ten pieces of blue-and-white porcelains in the Jingdezhen Ceramic University Museum were examined using energy-dispersive X-ray fluorescence to reveal the chemical compositions in their microzones. Four key findings were obtained. Firstly, the Co-based material used in the specimens was imported ore with high Fe and low Mn contents, with certain quantity of Ni and As. Secondly, the bow-string and main patterns had different (Fe+Mn)/Co ratios, with the main patterns having lower ratios, suggesting purer Co characteristics. Thirdly, the differences in the elemental ratios were verified using a historical purification process, whereby the main pattern was speculated to be painted with purified Co-based materials. Finally, the material differences that began to appear during the Yuan Dynasty, which influenced the painting of blue-and-white porcelains in the Ming and Qing dynasties, were investigated. This study provided with a new perspective on the Yuan Dynasty blue-and-white porcelains and the development of decoration systems for Chinese blue-and-white porcelain paintings.