Creating Wusetu (“Five-Coloured Clay”): Chronological changes in Zisha ware clay recipes and the complexity of potters’ technological choices

Abstract Technological choices in pottery production, particularly the selection of raw materials, are much discussed for prehistoric periods but have received little scholarly attention in the case of Late Imperial China. In this paper, zisha teapots, which became China’s main tea preparation vessels over the course of the 15th–twentieth century, are presented as a case study to explore the complexity underlying potters’ raw material selection in historic periods. A total of 187 excavated zisha sherds was analysed using optical microscopy, semi-quantitative chemical analysis via scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) spectroscopy, and ImageJ analysis of SEM backscatter spectrum images. These zisha sherds date from the Ming dynasty to the Republican period (1368–1949) and were recovered from Shushan kiln site. SEM–EDX analysis combined with image manipulation in ImageJ revealed changes in the clay recipe over time, including an increase in iron oxide variation and increasing fineness of clay particle sizes, suggesting an expanded colour range and refinement of the clay paste. Combining these findings with an examination of the geological setting of the mining locations, the clay procurement sequence, the clay-processing techniques used by the potters, and texts discussing clay colour and texture appreciation, this study demonstrates the complexity of the potters’ raw material choices in Late Imperial China and illustrates how these factors can be elucidated through a combination of scientific analysis of archaeological material, examination of geological samples, visual analysis, and reference to historical sources.