Vessel in the Shape of a Bird - Public domain museum image. A black and white photo of a vase

The san tsai technique dates back to the Tang Dynasty. Despite the name, the number of glaze colours used to decorate wares from this period was not usually limited to three. Traders in the West sometimes referred to Tang-era san tsai wares as 'spinach egg' because of their use of green, yellow and white (although the latter colour might more accurately be called 'amber', 'not quite white' or 'cream'). San tsai wares were made in northern China, where white kaolin and fired dark yellow secondary kaolin and refractory clay were used to make pottery. These raw materials contained very little iron. The wares were covered with white clay and glazed before firing. Due to the high plasticity of the material, intertwined underflows were formed on the piece, creating coloured patches and stripes on the surface. At kilns in Tongchuan, Neiqiu County, Hebei Province, and Gongxiang, Henan Province, the clay used for ritual wares was similar to that used by Tang Dynasty potters. The ritual wares were fired at a lower temperature than the white porcelain of the period. In some cases, the figures in the set were personalised by hand engraving.