Is the most common source of calcium in glazes. It is a high temperature flux that gives durability and hardness to glazes.
Whiting 325 mesh - standard material used in pottery glazes. 98.0 % CaCO3 with 1% retained on a 325 mesh sieve
Also know as Calcium Carbonate, alone is quite refractory but when mixed with feldspar or silica will start fluxing around 1100°C. It is often used in low fire clay bodies as an addition to help with glaze fit. It is rarely used as a flux in stoneware or porcelains.