Macro crystalline glazes are most likely not a Japanese invention. They first started to appear on the scene in Europe during the 1850s. They pose some of the most difficult challenges that a potter could face. This challenge might be why they’ve caught on among so many Japanese yakimono artists.
Combining porcelain and crystal glazes works especially well when fired in gas kilns. Those who remain patient should experience the best results. Outside observers may be most surprised by the recipes used to make the glazes. Those who try to do too much at once are usually fooled by this simplicity.
Crystal glazes are generally made from a frit, zinc oxide and silica. Titanium dioxide, lithium carbonate and bentonite are generally preferred when working with supporting agents. Most of the brilliant appearance of these pieces actually comes from the brilliant glazes. Colorants don’t all work at the same temperature, so it can be hard to mix them together at times.
The firing profile along with the thickness and angle of the glaze has a lot to do with the success chances of any macro crystallization project. While most people are aware that the top temperature of the firing and the atmosphere in the kiln influence the macro crystallization process, fewer people are familiar with all the other variables that go into it. The temperature at which the artist bisqued the green clay can have a profound influence on the art. The temperature at which the clay was soaked can also influence the growth of crystals.
Artists who try to rush the process never get anywhere. Working with precise equipment can help a lot, though. Traditionalists might scoff at the idea of using computer software to control a kiln, but this method allows artists to fire reduction glazes that they wouldn’t be able to any other way. Gas kilns were previously unheard of in the field of firing crystals.
Nevertheless, gas kilns actually produce brighter and sharper crystals than most electric kilns could. Individuals who get really into the art will probably start to experiment with nickel oxide. That compound can make some large crystals. Keep in mind that porcelain is more expensive than regular stoneware, though, so patience will be rewarded.
Those who have to throw out many of their pieces will end up shelling out a good bit of money as a result. Crystal pieces tend to fetch more on the collector’s market since porcelain is worth so much more than stoneware.