ZHANG Zigang, GUO Yenyi, CHEN Yaocheng

(Shanghai Institute Of Ceramics Academia Silica)

Abstract: This paper deals about one piece of the blue-and-white ware excaveted from the ruins of an. ancient city of Tang Dynasty in Yangzhou region, and six pieces of blue glaze for the Tang tricolor use. These sample pieces were tested by means of chemical analysis and optical microscope. By comparing the pigments, glazes and bodies of tricolor blue glaze and Tang blue-and-white with those of Jingdezhen, Zhejiang blue and-white ware and the color glaze of T'un-,guan kiln area in Hunan Province,we found that:

(1) the ratios of MnO/CoO, Fe₂O₃／CoO and CoOaCuO in the T'ang; tricolor blue lead g;laze are 0.03, 0.97-1.0l and 2.7— 4.4 respectvely. The ratios of MnO/CoO and CoO/OuO in the blue pigment of Tang blue-and-white are 0.2 and l.2 respectively, which are quite similar to the former, but very different from the blue pigment of the blue-and-white of Song, Yuan, and Ming Dynasties in Jingdezhen, Zhejiang and Yun'nan areas. The fact shows that a kind of intergrowth cobalt ore with a certain amount of copper ore might have been used for blue-andwhite and tricolor cobalt blue in T'ang Dynasty.

(2) the Tang blue-and-white body containing high alumina (28.7%) and low silica (63.81%), with its glaze containing high calcium oxide (14%), is characteristic of the pottery body of Gongxian county in He 'nan Province, which shows that the early T'ang blue-and-white could have been made in Gongxian area.

(3) the blue pigments for blue-and-white from T'ang to Qing Dynasties are cobalt ore which can be categorized into three kinds: Cu-Co intergrowth cobalt ore which contains low amount of MnO, FeCo intergrowth cobalt ore which contains low amount of MnO and high amount of Fe1 01, and Mn-Co intergrowth cobalt ore which contains high amount of MnO and Fe₂O₃.

Keywords: Blue_and-white, Tang Dynasty