The introduction of celadon production in North China: Technological characteristics and diversity of the earliest wares

Celadon, technically a stoneware with a lime-rich glaze, had been produced in South China for more than two millennia before it was first made in the North in the second half of the sixth century. It appears to have been an immediate precursor to white porcelain, which was first produced by northern kilns. The compositions and microstructures of early northern celadons from kilns, residential sites and tombs in Shandong, Hebei and Henan provinces, and dated 550s-618 CE, have been determined by SEM-EDS. The majority of the vessels were made using a low-iron kaolinitic clay, with high alumina (20–29%), as anticipated for northern clays. A small number of celadon vessels from a kiln at Caocun, which produced mainly lead-glazed wares, have lower alumina contents and appear to have originated in the South. It seems possible that these imported vessels were being used by the potters as models on which Caocun wares were based. Consistent differences in major element composition are observed between the products of kilns at Anyang, Xing, Luoyang and Zhaili. Unlike southern celadon glazes, which were prepared as two-component mixtures of vegetal ash and body clay, the northern celadon glazes are three-component, and typically contained an additional siliceous component, probably loess. An exception is the glazes of the Xing celadons, which present no evidence for loess but which are rich in Na₂O. The source of the soda is unclear, common salt and albitic feldspar are discussed as possibilities. Based upon micromorphological characteristics such as the relative size and abundance of remnant quartz and the extent of observable mullite, as well as the position of the glazes in the CaO-Al₂O₃-SiO₂ phase diagram, the Xing bodies are more mature and they appear to have been fired to higher temperatures than the products of other kilns. These results suggest that celadon technology was not directly transferred to the North from the South, but that the northern potters adopted their own strategies to make high-fired glazes. Furthermore, each kiln appears to have had its own preferred recipe, to suit the available raw materials. The products of Xing kiln were exceptional and it appears that here the trajectory towards white porcelain was already apparent, perhaps reflecting the creativity of the Xing potters who were among the first to make a successful white porcelain.