Duncan CR879 Color Burst Crystal Chips, Green Thunder, 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. Non-toxic  Food safe  Fires to cone 06 to 6 AP Certified Non-Toxic. Made in USA.