Crystalline Process

imageExploring the fascination of growing crystals in molten glazes has been an exciting facet of my work for the past 16 years. I began by attending a workshop at Ghost Ranch in New Mexico in 1991 with Willard Spence & Jim Kempes. I always wanted to learn how to make and use this glaze and once I finished the workshop I became addicted to them. The process of growing crystals is complicated one, but it has great rewards if one is patient and willing to keep trying when difficulties arise.

In order to fire Crystalline glazes, two pieces must be thrown and trimmed. One, the final product (vase, t-pot, bowl, etc…) and the other, a pedestal with a catch basin attached. The pot is glued to the pedestal with a mixture of white glue and alumina. During the firing, the glue burns out, leaving the alumina to keep the pieces from fusing.

imageMost of the glazes that I use contain large amounts of Zinc & Silica. Because of the high zinc and silica content and low alumina content, the glaze is very runny. The movement of the glaze aids in crystal growth. The kiln is fired to a temperature that melts the glaze, usually about 2300 F and then is backed off 200-300 degrees and held for a specific time – usually about 2.5 to 4 hours. During this time, the glaze is still molten and the crystals form from the nuclei of the Zinc Silicate that saturates the glaze. The crystals continue to grow while the kiln maintains this lower temperature. Once the soak is finished, the kiln is cooled slowly.

Once the kiln cools, the pots are removed. At this point I determine whether the glaze is satisfactory or if the pot needs to be re-fired. Once I feel that a piece is finished, I chisel it off of the pedestal. Because the glaze runs, the catch basins have glaze pooled in them. The pedestals, having served their purpose, are discarded. The bottoms of the pots are then smoothed on a sanding disc. The beauty of the glaze is that there is no way to plan the outcome. The crystals grow at random and although the process can be controlled somewhat, the end result is always unique.