In crystalline glazes, the crystals form through a complex process that mirrors the geologic conditions found in volcanoes. Intense heat allows molecules to move freely and combine, then are trapped as the molten material cools. The glaze is applied thickly to form a layer in which the molecules can travel. As the glaze is heated to a molten state, the molecules move about, are attracted to each other and join together in patterns based on their molecular bonding affinities.
The kiln is then cooled and held at a controlled rate to specific temperatures so that the different types of molecules join together to form lattice structures. Varying the firing schedule can produce halos, frills, curving crystals and many other variations. If all conditions are just right, beautiful crystals are captured as the glaze cools and hardens. No two pieces are exactly alike.
The glaze is so fluid that it runs off the pot so the pots are placed on special catchers to contain the molten glaze. These catchers must be cracked off of the pots and the bottoms ground to achieve a smooth foot.
I constantly experiment with many variables, and find it always a gift to open the kiln and see the variety of crystals that have formed. I have painted with molecules and played God in my own personal volcano.