ZHANG Zhigang  GUO Yanyi

(Shanghai Institute of Ceramics, Chinese Academy of Sciences)

LIU VHeying

(Hebi City Museum, Henan Province, China)

Abstract: The underglaze decoration porcelain in the early Tang dynasty found at Hebijiyao site, Henan province, was the earliest in the North China after the discovery of blue-and-white porcelain at Gongxian and underglaze colour porcelain at Tongguan kiln, Changsha. The conclusions obtained from the research are as follows: 1. The main colouring element is iron, not cobalt. 2. The glaze belongs to calcium glaze. It contains RO 16.37% and R20 1.99% and has the same composition used in the early Tang dynasty.3. The body belongs to high Al₂0₃ one in the mineral composition of clay-feldspar-quartz system. 4. The engobe layer between the body and glaze is a thick­ness of 500 micrometer and its Al₂0₃ content is higher than that in body, but Fe₂0₃ con­tent is lower, and particle size is finer. 5. The ware was fired at 1150士20℃ in the weak re­ducing atmosphere. The water absorption of body is 5.6%.

Keywords: ancient pottery and porcelain, underglaze decoration, Hebijiyao