Crystalline glazes are specialty glazes that show visible and distinct crystal growth in the matrix of the fired glaze. The macro-crystals found in crystalline glazes form around a nucleus of a tiny titanium oxide or zinc oxide crystal. In the right circumstances, zinc and the silica oxide molecules will begin attaching themselves to the nucleus crystal. These molecular bonds are in very specific arrangements, which we see as crystals.
Crystals take a long time to grow. In order for this to happen, the glaze must remain molten for an extended period of time. Firing schedules for crystalline glazes usually require a soaking period at the end of the temperature gain, plus a controlled cool down. Below are some of the crystal formations I have been able to achieve.