CALCINED KAOLIN / CHAMOTTE
Chamotte is a calcined clay. The calcination process takes place in a rotary kiln at high temperatures of 1400 - 1600ºC. Sanitaryware pieces are fired at lower temperatures of around 1200ºC, therefore the chamotte is inert at the firing stage and acts like a skeleton to produce ware with better proprieties. Grog is composed of 40% minimum alumina, 30% minimum silica, 4% maximum iron(III) oxide, up to 2% calcium oxide and magnesium oxide combined. Its melting point is approximately 1,780 °C (3,240 °F). Its boiling point is over 9,000 °C (16,230 °F). Its water absorption is maximum 7%. Its thermal expansion coefficient is 5.2 mm/m and thermal conductivity is 0.8 W/(m•K) at 100 °C and 1.0 W/(m•K) at 1000 °C.
