Don & June MacDonald on tue 29 jan 02
I have recently returned from a trip to Thailand. While there I visited
several ceramic factories, mostly those doing celadons. All the
celadons were crazed. Later I went to visit a craft village near Chaing
Mai, and was able to ask a few more questions as the people involved
spoke English. Turns out that they bisque to 800 degrees C. which
strikes me as rather low, then fire to 1240 C. for the glaze firing.
Couldn't find out exactly what was in the glazes, but the celadon was a
lovely robins egg blue, but very crazed on all pieces. I wonder if the
low bisque has something to do with the crazing. By the way, I highly
recommend Thailand as a vacation destination, the tourist infrastructure
is so well organized, we would go back in a minute.
June from B.C.
Craig Martell on tue 29 jan 02
Doug responded to Denise:
> feldspars do often contain some trace amounts of alumina.
Hi:
Actually, it's a lot more than a trace. Potash feldspars average about 16%
alumina. G-200 for example has about 18% alumina and only 10.8%
potassium. So, if you consider the alumina to be a trace amount, the
potash content would be really miniscule.
regards, Craig Martell in Oregon
Doug Gray on tue 29 jan 02
Denise asks---
Are there many glaze recipes without clay?
Many of the traditional celadon glazes from Korea, China and even Japan
have little or no added clay. Of course, they consisted of mainly
feldspars and feldspars do often contain some trace amounts of alumina.
And your assumption about crazing is correct. Many of these glazes did
craze even on porcelain.
Doug, SC
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