Crystalline glazing is a process that involves a precise balance of clay, glaze, temperature, time, and form. If any one of these five parts of the process is not controlled in the intended way of the artist, the results will change. Because of this delicate balance, every variable possible must be addressed to give the best opportunity to make a successful crystalline glazed piece.
A crystalline glazed work of art starts with choosing the correct clay body for the desired results. The clay body that provides the most brilliant results is porcelain. Compared to other clay bodies, porcelain has the least amount of impurities, which yields a smooth, white, and blemish-free canvas to apply the glazes. The second step to create a successful crystalline piece is formulating a crystalline glaze recipe with the correct ingredients. Crystalline glazes contain three basic ingredients necessary for crystal growth: zinc oxide, silica (or ground quartz) and a frit which is fused glass that is ground to a fine powder. These three ingredients are mixed with water to form a thick glaze which is then applied to the pot. Various metallic oxides such as copper or cobalt oxide, iron, manganese or nickel oxide are added alone or in combination to give colors ranging from white to blue, green, gold, purple, orange, etc.
Once the glaze has been applied to the piece it is then fired in the kiln to 2300 degrees. Once this temperature is reached the kiln is cooled quickly to suspend the runny glaze on the piece. The kiln must be maintained at this lower temperature for several hours to allow the crystals to grow. Since the glaze runs down the side of the piece it is important that every piece gets its own glaze catcher that it sits upon. This is to ensure that the glaze doesn’t ruin the kiln self that it is placed on. Every glaze catcher has to be then removed and the piece has to be ground flat with a diamond plated grinding disk. The crystalline process contains so many variables that consistent or predictable results are almost impossible to obtain.