Duncan Crackle & Crystal Glazes emerald falls CR903 4 oz. [PACK OF 3 ] Duncan Crystal Glazes are nontoxic gloss glazes that contain glaze crystals that melt and flow during kiln firing The easiest glaze to apply, each of the Crystal Glazes are different. Some glazes contain crystals of just one color, while others contain several different colored crystals. Due to the unique multicolored bursts and specks while firing, you will have a different finish every time! AP Certified Non-Toxic. Made in USA! Fire to cone 06