GROG - Materials to strengthen clay.
Grog: is a granular material that has been crushed down from brick, refractory rock, or other pre-fired ceramic product and added to clay to give textures, reduce shrinking during firing, help the clay to form uniformly and stop cracking and warping when being fired. Grog can be made of many varied substances, of different thicknesses and colors. Make sure the grog can be fired to the same or higher temperature than the clay it is going to be added to. It can be obtained from cutting or filing tiles. When using an electric tile cutter it throws off bisque in powder form, which is grog.