•The secret to cool bodies and glazes is a lot of testing.
•The secret to know what to test is material and chemistry knowledge.
•The secret to learning from testing is documentation.
•The place to test, do the chemistry and document is an account at https://insight-live.com
•The place to get the knowledge is https://digitalfire.com
Cristobalite is a crystalline form of silica. Silica normally exists in nature as quartz. But cristobalite is available as a powder, it is manufactured by mixing quartz with the right fluxes/catalysts and calcined to the necessary temperature (1100C+), then cooling it quickly. But such a material is not useful in traditional ceramics since it would convert back to quartz on heating. However, quartz particles in a clay body, such as a whiteware that does not fire too vitreous, find themselves in a mix of clays and fluxes that provides an ideal environment for the conversion to cristobalite. The firing temperature, fineness of the quartz particles (finer is better) and soaking time determine the completeness of the conversion.
Out Bound Links
Cristobalite at Wikipedia
Article about cristobalite in clay bodies
Cristobalite is a crystalline form of silica (SiO2). Silica has the rather amazing ability to exist in different crystalline forms (called polymorphs) each of which has subforms (e.g. alpha, beta). Each form has different physical properties. Quartz in the preferred most stable form, the one found i...
By Tony Hansen