The diatomaceous earth, when utilized, accomplishes three functions :

• It increases the thermal impedance of the mold coating to prevent the development of localized chills in the poured molten metal charge.
• It allows easy stripping or removal of the coating from the mold following the casting operation.
• It acts as an inert binder when the coating is applied to the mold.

Calcined Diatomaceous gives maximum volume stability which prevents swelling during the heating cycles.