Sax True Flow Obsidian Colorburst Glaze’s opacity is dependent on number of applications and is ideal for one-of-a-kind pieces since every application and every firing will produce different results. Creates multi-colored patterns as well as designs when fired. Create unique dramatic effects by combining other glazes of a similar firing range. Crystals will fade and turn blue when fired at Cone 6. Freeze/Thaw stable. Not dinnerware safe due to surface characteristics.