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12/12/2004: "A pottery glaze firing"

I fired a glaze kiln last night: porcelain and stoneware thrown this past summer. It was a very small firing; about a dozen coffee cups, a vase, and a medium size lidded casserole dish. It wasn’t my most successful. Two cups the glaze ran, one cup broke in the firing, and three cups developed fatal cracks while cooling. I glazed the inside of one cup red, and while the color is stunning, it pitted and bubbled in the firing--the pitting makes it junk. I ended up with three decent coffee cups, one small dogwood flower vase, and one nice casserole dish that my mother immediately confiscated.

There could be several reasons for the bad firing. If I had to guess I would say the most likely culprit for the cups breaking in the cooling was that I opened the kiln too soon and the cups cooled too quickly. The running glaze can be attributed to a soaking heat—my fault again. The cups themselves were made from left over porcelain clay that had come through the previous winter. The clay had frozen and separated, but I wedged it well and thought it would do fine: it handled beautifully on the wheel, but it could have been a contributing factor in the cracking.

There is no real telling. That batch of clay is gone and I won’t be throwing again until late spring.

On a positive note the colors were all brilliant: mostly Spectrum cone 6 greens and blues that I had not worked with before. One combination in particular: a Wedgwood Blue exterior, white interior with a Cascade Green rim dipped about an inch. I would never have expected to achieve such beautiful coloration in an electric kiln. .