Research on bluish-white porcelain glazes of Fanchang kiln in China

Polarized light microscopy, thermal dilatometery and energy-dispersive X-ray fluorescence spectrometry (EDXRF) were conducted to analyse the microstructures, sintering temperature and chemical compositions of ancient porcelain glazes excavated from Fanchang kiln, China. The origin, development and decline of Fanchang bluish-white porcelain were thoroughly investigated from the perspective of the formula and firing technology from the Five dynasties (907–906 CE) to the middle Northern Song dynasty (1015–1070 CE). The contents of major elements in glazes were compared with those of Ding, Yue, Qingshan and Hutian kilns over the same period. It was indicated that the glazes of Fanchang bluish-white porcelain were prepared by mixing limestone and plant ashes into the ‘glaze stone’. After the middle Northern Song, the content of limestone and plant ashes gradually increased, which was related to the change of raw materials and the formula technology. The glaze formula of Fanchang kiln was much closer to the southern kilns. Evidence revealed that Fanchang bluish-white porcelains had reached a high firing level in the Five dynasties. At that time, the firing temperature was maintained in the range of 1100–1220°C, and their colour and texture showed at their best. In the middle Northern Song, the quality decreased as the firing temperature decreased, implying signals of a gradual decline.