Duncan Color Burst Crystal Chips, Set of All 8 Colors, Add to Ceramic Glaze for Unique Effects After Kiln Firing Duncan Color Burst Crystal Chips will make your ceramic art projects explode with an eruption of color! Mix these crystal with any ceramic glaze and after kiln firing the crystals explode with bursts of color. Crystal chips will react differently in the firing process depending on what glaze you pair them with, changing the color, burst size or amount of flow. Set includes one 2 ounce bottle of each of 8 colors! Fires to cone 06 to 6. AP Certified Non-Toxic. Made in USA. Crystal Glazes are nontoxic but due to a possible crazing nature, not all colors are food safe.