Glazes and Kiln Firing
Part Two: The Ceramic Building Process

Ceramic artists make a point to explain how volatile the whole process of ceramics can be. Clay bodies can differ from one batch to another and water for your glazes change for whatever reason, perhaps due to a relocation of your studio.

These folks went to great lengths to experiment with their materials until they arrived at a suitable combination for the style of ceramic they seek to create. A very complex process. Some get there by accident and others stick to an almost scientific recipe and enjoy success until one day perhaps the clay body they’d been buying produces subtle changes or even fails during the firing process. Then they go at it again, trying to make the adjustments necessary to stabilize the mixtures.

I chose two artists who produce with great success, but with completely different ceramic types: Thrinley DiMarco of San Juan Island for Raku, who has decades of ceramic experience, and Joe Symons of Orcas Island, who more recently found the love of ceramics and has spent several years working an exclusive process-using glaze that produces crystals.

Other than for the similarity in using a porcelain clay body type, their glaze and kiln work is very different. Raku has a dark and textured surface with various patches of metallic coloration, while the Crystal pots generally display smooth surface texture and a more predictable color, and the prized crystals produce random patterns within the glaze.

As for any ceramic process, the greatest factor is in the firing, of which there are three components: clay, glaze, and kiln. The ingredients for glaze and clay will vary. A base glaze will begin with water and the addition of powdered ingredients. Characteristics in glazes can range in transparent to opaque, the finish can be shiny, matte, or satin, may have texture or be smooth, or have density. Color is then added from heavy metals in the form of powder: copper for green, blue is from cobalt, iron gives browns, and nickel is for a blue/green.

As for clay bodies, Thrinley described her preference for low-fire white clay without lots of talc for her Raku, with occasional use of a high-fire white clay body called Colman Raku. Joe says only the finest porcelain clay body will provide the best crystals formations.

In either case, Raku and crystal pots are most affected as an end product by the kiln or firing procedures. The process for Raku is to withstand a lot of thermal shock and extreme temperature changes. Crystal pots like lengthy high-firing and require evenly distributed heat for best results throughout the kiln.

One synthesized version of the Raku firing process is after the bisque firing and the application of the glaze has dried, a very fast firing of 15 to 16 minutes at 1750 to 1900 degrees, depending on the glaze. The piece is then removed directly from the hot kiln and often a smoking process takes place, where the piece is placed in an open fire pit using any number of organic materials such as dried grass, pine needles, saw dust. A hand torch can also be used. The pots are pulled from the fire and evaluated for color, which change before your eyes. As you determine the moment to "freeze" or "lock" that color pattern, the pot is dipped into cold water–another thermal shock.

The Raku process is a big contrast to Joe’s crystal ceramics, which are extremely fussy about their firing environment. The real excitement for me to visit Joe’s studio was seeing his big kiln: a side load drawer rolls on tracts, it’s gas fired, and equipped with an electronic timing system and thermostat. He loads during the day, begins firing at 6pm with the timer set to end the cycle at 9am the next morning, and will cool down until 6pm that evening. The kiln produces extremely efficient and stable heat distribution, a beautiful piece of equipment that takes the hassle out of an otherwise tedious task of kiln watching. Of course it has taken Joe trial and error to devise the timing and heat structure to confidently fire his pots, and they are beautiful.

The experimentation process, which these two artists continue to pursue in the world of ceramics, is no doubt impressive. You can lean more about Joe Symons and his crystal pots and gallery locations by visiting his Web site, www.HotIceOrcas.com.

Although Thrinley is currently beginning the process of building a new studio, you can find a sample of her past work on www.sanjuanartistcommunity.com/dimarco .