Crystalline Glaze Technique
I enjoy the varied patterns and appearance of depth created by crystalline glazes. Examining the crystals closely shows unending variations. The crystals form from and grow in the fluidized glaze at high temperature during the glaze firing.
The process required for crystalline glazes is labor intensive. Each piece, after bisque firing, must be glued to a bisque fired, clay pedestal that fits the base of the piece exactly. Then, the glaze is applied. I have found that spraying the glaze on the piece relatively thinly works well for me. Because some of the glaze will run off the pot, a clay catch basin must also be prepared and bisque fired. Once the glaze is applied, the piece and its pedestal are placed in the catch basin. The whole assembly is then carefully placed in the kiln for the final glaze firing.
The glaze firing requires a kiln in which the temperature can be carefully monitored and controlled. Crystalline glaze firing schedules can require two, three or more temperature manipulations and hold times. This is quite different from a typical ‘increase to temperature and cool’ glaze firing.
Following the glaze firing I separate the piece from the pedestal and catch basin by applying heat from a torch to the pedestal below the base. The thrown pedestal and catch basin are discarded. Then, the bottom of the piece must be ground down to smooth the glass edge at the base.
Crystalline glazes are a lot of work but I enjoy the results and I hope that you do too.