Traditional craftsmanship and technology of Jianyang black wares from Fujian, China

A study was conducted to demonstrate variations in materials, fabrication techniques, and firing and cooling regimes produce variations in microstructure that control the appearance. To establish and quantify variability and to gain insight into the crystallization and thermal processes, thin-section petrography and image analysis was used to examine and quantify features of the ceramic body and glaze. The physico-chemical mechanism that promotes the hare?s fur and oil spot appearances consists of firing above 1230 °C up to 1300 °C, and controlling the glaze viscosity by varying the time at temperature, oxidation state, and mixture of raw materials. If the glaze is more viscous and does not flow by lowering the temperature (undercooling) or lessening the time at peak temperature followed by heating to grow the crystals, the oil-spot appearance is produced. X-radiographs show diagonal alignment of elongated pores from 30 to 45° above the horizontal that is common in rapidly thrown bowls made with minimal wedging. The continuous size distribution indicates that the inclusions are natural components of the clay. Total optical porosity is 7%, and the iron-bearing clay constituent and fine porosity is about 83%. The agglomerated clay areas indicate the glaze was poorly ground and poorly mixed to promote heterogeneous crystal growth.