These spectacular crystals are wonderfully three-dimensional. While some crystalline glazes seem "impossible," by using these glazes and the following firing schedule, you'll be amazed at the beautiful crystals that will appear! This firing schedule may require adjustment in different kilns and under varying conditions. Select from stock colors, or blend your own choice of stain or oxide to the base glaze, WC-160. These glazes are lead free and certified nontoxic. Excellent crystal growth results in slightly raised crystal structure.