ZrSiO4—zircon opacifier—inert dispersoid in glaze melt—low-cost substitute for tin oxide—use double the recipe weight of tin. Includes Zircopax, Opax, Superpax, Ultrox. All are toxic in inhalation. Source: Clay: A Studio Handbook
Sign up for your FREE subscription to the Ceramic Arts Daily Newsletter and we will give you How To Use Clay Pencils, Slip Trailers, Glaze Pens, and Carving Tools to Decorate Ceramics Free!