Crushed up bisque clay sifted through various sizes. Bought and sold by their general size. It helps by preventing cracking from worsening, shrinkage not as bad, and gives more body to clay. A drawback would be that the plasticity suffers and the texture is a blessing/curse depending upon the project.

However, the grog itself opens up the clay body and seems to prevent the drying out the body too badly. For such tight bodies as porcelin it seems to dry too fast and unevenly--not so bad with a liberal amount of grog, I like the rough tecture tho, sucks for burnishing.