Feldspars are important ingredients in clay bodies and glazes. In both applications, their primary function is to supply ﬂuxes to the formulations, but they also provide additional alumina (Al2O3) and silica (SiO2). Feldspars are naturally occurring minerals and are generally classiﬁed as either potash (potassium) or soda (sodium) feldspars based upon the predominant alkali metal element (the ﬂux) that is present. The minerals commonly referred to as lithium feldspars are not true feldspars, but they are aluminosilicates like feldspars and contain the ﬂuxing element lithium, and are used for the same purposes as the feldspars.
Rosette Gault, an expert on paper clay, explains some basics of paper clay preparation and takes you through the process with some step-by-step photographs. Plus she gives some health and safety tips for working with paper clay.
The objective is to locate one single earth material that alone almost provides the desired surface, and then to add as few additional materials as possible. I call this primary material, which almost achieves the desired glaze surface, a “glaze core.”