Microstructural Analyses of Salt-Glazed Ceramics

Defining features of certain salt-glazed studio pottery are a surface texture akin to orange peel, with mm-scale dimples across the ware, and fine scale cracking within the salt glaze. There is remarkably little information in the scientific literature to explain the reasons for the formation of the orange peel effect or to specify the length scales due to this fine scale cracking. Here, salt glazes on ceramic wares have been characterised by light microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction to ascertain the thickness and chemical composition of the glazes and the nature of any crystalline phases present, and also to quantify the length scale of the crack patterns. It is proposed that the orange peel effect is produced as a consequence of local chemical inhomogeneities within the salt glaze affecting its local viscosity, and therefore its local ability to flow during maturing of the glaze.