Archaeometric investigation of the relationship between ancient egg-white glazed porcelain ( Luanbai ) and bluish white glazed porcelain ( Qingbai ) from Hutian Kiln, Jingdezhen, China

Hutian Kiln, located in Jingdezhen City of Jiangxi Province of China, is well-known for the productions of bluish white glazed porcelain (Qingbai) from Song Dynasties (AD 960 – AD 1279) and egg-white glazed porcelain (Luanbai) of Yuan Dynasty (AD 1271 – AD 1368). Luanbai with an opaque glaze is thought to have evolved from Qingbai, which has a transparent glaze; however, the precise technological details for this process have not been adequately studied. This paper presents the analyses of samples of Luanbai and Qingbai porcelains from Hutian Kiln using various microscopic studies, including visible light spectrometry and Energy-dispersive X-ray fluorescence. Some distinct technical changes have been identified that help to explain the evolution from transparent Qingbai to opaque Luanbai glaze. First, there is an increase in the proportion of potassium-rich ingredients in sherds dating to Late Song Dynasty, which suggests a change in the glaze recipe. Second, during Yuan Dynasty, both types of porcelain share the same chemical composition, but Luanbai products display distinct micro-structures and opacity in contrast to the Qingbai ware. Third, the overall firing temperature of Luanbai is around 1270 °C which is generally around 100 °C higher than that of Qingbai. The opacity of Luanbai ware may be the result of different firing techniques, including the higher firing temperature and a correspondingly longer time to heat and to cool the glazed porcelain. The results reveal new insights on the coloring mechanism of the two kinds of glaze and the transition from Qingbai of Song Dynasty to Luanbai of Yuan Dynasty.