Crystalline made at Eck McCanless Pottery contains large crystals that are formed from zinc oxide. The three main ingredients used to produce crystalline are zinc oxide, silica (ground quartz) and frit (ground glass). Metallic oxides are also added to the glaze to create vivid colors.
The crystalline process requires several steps and is difficult to master. Even seasoned pros sometimes have mishaps due to the nature of the glaze, which melts in the firing and becomes very runny. The runniness of the glaze requires crystalline pots to be placed on pedestals, which are then placed on a dishes to catch the excess glaze and keep it from ruining the kiln.
Occasionally, one of the pots will fall off its pedestal in the firing, which can create real havoc. In the photo to the left, a pot fell over and hit another pot. That pot tipped into another, and another, and so forth. The pots became fused together, making them unfit to sell. Seven pots and a kiln shelf were ruined, and the kiln walls were damaged during this mishap. Luckily, this doesn't happen very often.
Crystalline pots are fired to a peak temperature of around 2,300 degrees fahrenheit. Once peak temperature is reached, the temperature is lowered about 300 degrees. The kiln stays at this temperature for several hours, which allows the zinc crystals to form. The placement and the number of crystals on the pot is completely random. Potters have no control over where they form or how many make an appearance.
Eck makes his own glazes from dry ingredients. In the photo on the right, he is applying the glaze to the pots with a paint brush. At this point, he has already glued them to pedestals. The next step is placing them in the kiln. The photos below show pots being placed onto their catch dishes inside the kiln and the results after the firing.
The pots in the kiln are still not ready to greet the public. The next step is to remove the catch dishes and pedestals. Eck taps the bottom of the catch dish with a hammer to get the dish and pedestal to release from the pot. He then uses a grinding wheel to smooth the bottom of the pot and get rid of any rough edges. If you look closely at the photo on the left, you can can see the dish falling into the bucket after releasing from the pot.
Eck sometimes creates suspended crystalline pots (right). These are suspended above a dish that collects the run-off glaze to create a pool of crystalline. Decorative sculpted posts hold the vase and dish in place.