Feldspar as a mineral and classify feldspars as mainly as albite, microcline, orthoclase and anorthite. Generally high potash feldspars are employed in bodies and promote vitrification by forming a glassy phase that ‘cements’ more refractory particles together and triggers the formation of mullite from clay mineral. In glazes feldspar promotes melting at medium and high temperatures (feldspars are the primary ingredient in most high temperature raw glazes). Sodium feldspars are most common and used mainly as a source of alkalis. Feldspars are mineral compounds of silica, alumina and fluxes and are among the relatively few insoluble sources of K2O, Na2O and Li2O. feldspars contain a complex mix of oxides, ceramic chemistry calculations are needed to ‘juggle’ a recipe to achieve the desired balance of fluxing oxides with alumina and silica and to control the high thermal expansion that they impart.

1. Potash Feldspar

High alkali base potash feldspar with white firing L value 80*

1. Soda Feldspar

High alkali base soda feldspar with white firing L value 78*