Nought-point-two per cent titanium dioxide: A key to Song ceramics?

Abstract

The high-fired ceramics of Song China (960–1279) owe most of their glaze colours to iron oxides, generally in glass-solution, although occasionally in crystalline suspension. There is though, another metallic oxide that has been present in high-fired Chinese glazes since their first appearance in the early 16th C BCE through to modern times. This is titanium dioxide (TiO2, titania), a natural impurity in most rocks, clays and ashes and in the clays and glazes made from them. Titania is not a true glaze colourant but it can turn iron-blue glazes green by oxidising some Fe2+ ions to Fe3+ at full kiln temperatures. This rather obscure reaction has recently been studied scientifically and is now regarded as a key factor in the broader understanding of China’s high-fired ceramics, particularly those of the Song Dynasty. Titania’s influence on glaze colour has also proved important in understanding China’s ancient and extensive ash-glazed stoneware tradition, the development of Chinese white porcelain in the Sui Dynasty (581–618), the creation of Jingdezhen’s porcelain industry in the early 10th C CE, the manufacture of the finest Song imperial stoneware glazes, and the vast production of porcellanous celadon wares that developed in south-eastern China from the 13th to the 15th Cs.