Paris Resto and Culinary: Chao Zhou Clay Pots by the Wu's

Yuan Xing Hao is established in 1847 in Feng Xi (Chao Zhou area), Guang Dong Province, known to be the best local pot maker. This batch of pots (20) are made of sandy Zhu Ni (local Chao Zhou red clay) by Wu Pei Liang.

Wu's family has its own secret recipe for clay. What's known to outsiders is the basic process. Raw clay materials are ground into dust, sifted and soak in water for 2 years, then drained and made into blocks of damp clay put away for 10 years before use. Small grains of sand are added for texture and also to increase porosity. There are 2 standard types of sandy grains used by the Wu's family.
1, raw clay materials ground into small grains then added directly into ready for use cured for 12 years clay. After firing, both clays shrink at similar rate, approximately 12%.
2, defected/broken pots are ground into small grains then added into ready for use cured for 12 years clay. After firing, clay shrinks at 12%, sands at 0%, therefore creates more pores.
Chao Zhou pots range from 2% to 5% porosity depending on the clay mix, each maker/family tradition have different recipes not shared with others. I do not have the answers to them, but all clays are pure, just different composition of texture and curing process.

Pots I currently have in stocks are mixed with the later type of grains therefore with higher porosity of up to 5%. Zhang's family pots are approximately 2% due to the fine clays are used.