Potential fingerprints for the usage of botanic ash in the glaze recipes of the Jizhou tea bowl

Abstract

A glaze slip made from a mixture of porcelain clay and flux was melted at high temperatures to form an amorphous glaze layer on a ceramic body. All information about the raw materials and recipes of the glaze was lost in this process, leading to difficulties in the reconstruction of the ceramic-making process performed in ancient China. Herein, the refiring experiment was performed and the thermal dilatometer (DIL), X-ray diffractometer (XRD), X-ray fluorescence (XRF) and field emission scanning electron microscope (SEM) were utilized to investigate the crystallization behavior in the glazes of an underfired Jizhou tea bowl. The results showed that diopside, fluorapatite, and anorthite crystallized from the heterogeneous glaze slip, induced by the inhomogeneity of the raw materials and the incomplete mixing process, during the firing process in the glazes of the Jizhou tea bowl. All these crystals melted with increasing temperature, indicating the importance of the underfired samples in reconstructing the ancient ceramic-making technique. Diopside and fluorapatite could be potential fingerprints to identify the usage of botanic ash in the glaze recipes.