Colouring mechanism and firing technology of white porcelain from the Sui Dynasty (581–618) from the Xiangzhou kiln, Anyang, China

Abstract

The Xiangzhou kiln was one of the first significant kilns in China to fire white porcelain and as well as the earliest one to adopt the technique of Make-up clay. It plays a very important role in the history of Chinese ceramics. Here we utilize ten pieces of Sui (581–618) white porcelain from the Xiangzhou kiln as the research objects. The chemical composition, micro-morphology, firing temperature, firing atmosphere, micro-area composition and other characteristics of white porcelain glaze were tested by energy dispersive X-ray fluorescence spectroscopy (EDXRF), laser Raman spectroscopy (LRS), optical microscope (OM), thermal dilatometer (TD), focused ion beam scanning electron microscope combined with X-ray energy spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and spectrophotometer (UV–Vis–NIR). Finally, the firing technology and colouring mechanism of the Xiangzhou white porcelain are revealed. Our study demonstrates that the relatively high content of Fe2O3 and TiO2 in the white porcelain glaze of the Xiangzhou kiln results in a milky white glaze with a slight greenish tinge. The high content of CaO and K2O in the glaze and the almost entirely glass phase of glaze layer lead to the fine grain, good transparency and gloss. Most of the white porcelain of the Xiangzhou kiln is fired at high temperature under reducing atmosphere. The Xiangzhou kiln white porcelain glaze belongs to the crystalline glaze, glaze disorderly distribution of some calcium feldspar precipitation crystals and a very small amount of quartz, calcite residual crystals, glaze bubbles are larger, the distribution of relatively dispersed. The overall colour effect of the Xiangzhou kiln white porcelain results from the combined action of the chemical colour of the body and glaze, along with structural colour.