Mayco Crystalites Crystal Glaze - S2723 - Grape Divine - 4 Ounce Jar These beautiful glazes transform in the kiln when small pieces of glass burst into color and intricate pattern during the firing process. Use alone for stunning effects, in glaze combination or simply as an accent to your design. Crystal glazes were designed to mature at cone 06/05. Apply to shelf cone 04 bisque. AP Certified Non-Toxic. Stir frequently as crystals tend to settle in the jar due to their weight. Made in USA.