Quartz inversion

The alpha to beta quartz inversion is one of the most important factors to be considered in the production of vitreous sanitary ware. [Maguire, Andrew. Graduate Thesis (n.20). Alfred University, 1958] Between 575 and 600 degrees celsius, there's a 2% expansion and 2% contraction on cooling. In this phase, alpha quartz turns to beta quartz and reverses during the cooling phase. It's recommended to fire slowly through quartz inversion as to avoid cracking. [Cushing, Val. Cushing’s Handbook. p43. Alfred, NY, 1994] Quartz inversion is an important silica reaction in firing clay bodies. The size of the silica particles is important in determining how easily the alpha and beta quartz contracts. Fine-grained silica will more easily change into non-contracting silica glass or sudden-contracting cristobalite, and thus not providing the proper contraction for a glaze. If the thermal expansion rates and contraction rates for the clay and glaze are different it will result in crazing and/or "shivering". [Obstler, Mimi. "out of the Earth and into the Fire". The American Ceramic Society. Ohio, 1996.]
Raw material samples, which have proven beneficial to decreasing the A to B quartz inversion "hump":
Talc-1.The formation of cristobalite and cordierite2.Fluxing of the silica
Nephaline Syenite-1.Taking the silica into solution
Petalite-1.Formation of cristobalite2.Fluxing of the silica
Alumina-1.Possible formation of mullite with the free silica2.The effect on the quartz inversion "hump" was not as evident in this material
Maguire studied the use of talc as a means to lower the maturing temperature of sanitary ware bodies. It would bring the body to quartz inversion earlier. [Maguire, Andrew. Graduate Thesis (n.20). Alfred University, 1958]

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