Kaolin grog is powdered insulating firebrick, a by-product of kiln manufacturing. Mix kaolin grog with just enough repair cement to hold the mixture together. Use to fill in damaged areas on the brick bottom or walls. Add kaolin grog to modeling clay to reduce shrinking and warping. Make custom kiln furniture by mixing 50/50 with fire clay. Inquire about economical large volume purchases. 5 lb. (2.26 kilogram) bag.