Plainsman Clays | WHIT
Whiting (Calcium Carbonate)
Whiting is calcium carbonate, and a common way to add calcium to a glaze. Calcium fluxes at high temperatures, so it is most active from about cone 4 upward.
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In a low fire recipe whiting is added for hardness, durability and opacity, since boron and the alkalis do the melting at those temperatures. From cone 6 it becomes an active flux, and at cone 9 and 10 it can strongly increase the melt. Higher calcium levels can promote crystalline matte surfaces during cooling. The same glaze can finish glossy or matte depending on the cooling rate alone. Nearly half its weight leaves as gas during the firing, though early enough that most glazes have not sealed over yet.
- Calcium carbonate, a common way to add calcium to a glaze
- Fluxes at high temperatures, with little melting below about cone 4
- High concentrations in an addition can promote matte surfaces during cooling
- Nearly half its weight leaves as gas during the firing
