Thursday, February 25, 2010

Ash Glazes and the Curious Pits

Last week, I arranged for a local glaze technician, Derik Spoon, to stop in and take a peek at some of the broken bits of pottery still out on the table. Long background story short, I took a pottery class at the local arts center, and imagine my surprise and excitement when the instructor informed us that he just moved to the area from a job as a glaze tech with a major producer of glazes available commercially to ceramic artists across the country... He agreed to stop in and take a look at what we recovered.

He immediately identified the type of glaze used on all of the pieces we had out on the table, and what he had to say ran contrary to everything we thought so far. Derik informed us that every piece on the table was glazed with an ash glaze.

Ash glazes, as Derik explained, are the simplest of glazes to make, consisting of processed ash mixed with clay and water. The ash typically is soaked and filtered through water to draw off the majority of the heavy alkali materials (a convenient by-product of this process is lye, a key ingredient for soap making; it would have been a sought-after product in any pioneering settlement with limited contact to larger supply networks), before being mixed with refined clay. Water is then added to the mix, and the mixture is applied to the vessels. Ash glazes leave very identifiable (to a trained glaze technician) markers on ceramics, including pooling or streaking of colors, and often a gritty appearance on the surface of the vessel. The effects of the glaze naturally differ depending on numerous factors such as the type of wood ash used, the type of clay used, the ratio of ash to clay to water, the firing time and temperature, the amount of fly ash in the kiln during firing, and the final cooling time of the wares in the kiln.

This all leads up to a new theory regarding the "random" ash pits located toward the front of the lot and the enclosed area of clay-like hard pack. These areas could very well have been where Thomas and the family were processing ash with various inclusions (bone, bisqued ceramics) for the purpose of color/effect experimentation, before mixing the ash with the refined clay to glaze the pottery. The material in the enclosure could be the refined clay used in the glaze mixture, or a large, ready supply of pre-mixed clay and ash drawn off of the neighboring ash pits. In any case, this is a very exciting revelation, and it offers possible explanations to the question, "What in the world was going on over there?"

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