Made of high-fired stoneware, and with an olive-green glaze, this jar is a precursor of the celebrated celadon wares of the Song and later dynasties. It was made in Zhejiang province, which lies south of the Nanshan-Qingling divide. Vital for an understanding of Chinese ceramics, this takes its name from two mountain ranges separating the loess plateau of north China from rice-growing southern China. Provinces north of this line are classified as 'northern China', have different raw materials from those in the south and their wares were fired in kilns of different design.

Archaeological evidence indicates that the first Chinese ceramics were produced in southern China, in about 9000 BC, at least 1,000 years before the earliest than northern wares. Southern potters used superficial deposits of locally abundant refractory clays. These are by definition resistant to heat and therefore needed a high temperature to mature, and in about 1500 BC true vitrified stoneware - fired at 1,150-1,200°C - made its first appearance in Zhejiang.

The first Chinese glazes were discovered by chance, when incandescent wood ash in the draught of a high-temperature kiln reacted with the clays of the wares. Potters were quick to make use of this natural reaction by deliberately applying wood ash to the raw clay, and, as on the later celadons, here they exploit the deepening of the colour where the glaze pools. The three ridges on the shoulders prevented the molten glaze from running at full heat, but have the added advantage of evoking work in cast bronze.