Study on the phase-separated opaque glaze in ancient China from Qionglai kiln

Qionglai kiln is a famous folk kiln site in China. Six pieces of opaque green-glazed porcelain shards with mild gloss and jade-like feel fired in the Tang dynasty (618–907 A.D.), were adopted as test samples. The correlation among composition, microstructure, firing technique and glaze appearance has been investigated by means of energy-dispersive X-ray fluorescence, field emission electron microscopy, direct transmission electron microscopy, X-ray diffraction and refiring experiment. The study has demonstrated that the opaque green glazes from Qionglai kiln site are high-temperature calcia–magnesia–silicate glazes and typical of phase-separated glazes. The liquid–liquid immiscibility structure plays a key role for the artistic appearance of the glazes.