From green to white: The technological origins of early white porcelain in Northern China

The appearance of white porcelain in Northern China during the Sui and Tang dynasties marks an important technological shift in the history of Chinese ceramics. How and why this development occurred from the established southern celadon tradition has been a long-standing question for researchers. In this study, samples of celadon, coarse white porcelain, and fine white porcelain excavated from a newly discovered Sui-Tang dynasty kiln site at Jinyang Ancient City, Shanxi, were analyzed for their composition. The results show that a local clay rich in calcium and magnesium was used for the ceramic body. A high-calcium lime glaze was commonly applied, and two distinct glaze formulations were identified based on the ware type. The glaze technology followed two distinct pathways: a common base of body material and plant ash was supplemented with either a silica- and iron-rich material to achieve the celadon glaze, or with a feldspathic mineral to develop the white porcelain glaze. These different technical choices indicate a progression from imitation to innovation. Celadon production followed southern techniques, but the low iron content of local clays required the addition of an iron-rich material to the glaze. This limitation, in turn, revealed the natural advantages of the local materials for making white porcelain, prompting a move from costly imitation toward more resource-efficient innovation. This change also drove improvements in paste refinement, glaze formulation, and the use of sealed saggers for firing. The case of Jinyang reveals a key process behind the origin of northern white porcelain: local, independent innovation was driven by a combination of resource constraints and the imitation of existing technologies. This work provides new physical evidence for understanding the technological origins and regional variations of white porcelain in Northern China.