Crushed high-fired clay graded in sizes from 15-mesh (very coarse) to 150M (extra fine) added as a source of filler or tempering grit to claybodies to reduce shrinkage and give structure for throwing or handbuilding. Does not shrink in firing, so in medium and coarse grades will show texture through thin to medium glaze. Toxic in inhalation. Source: Clay: A Studio Handbook