Tuesday, September 21, 2010

Boil, Little Porridge Pot!

I was reminded of this little line from a childhood story last night as I hovered over a large kettle of boiling water. I was subjecting three pieces of pottery to one of the most brutal tests you can imagine. It's called the Boiling Water/Freezing Water test and it is the acid test for glaze crazing. In a nutshell, you immerse a pot in boiling water for three minutes, remove it and immediately immerse it in ice water. After three minutes in the ice water bath, you quickly drop it back into the boiling water. You repeat this cycle three times. Once finished, you use a dauber and rub black ink or paint into the pot. After a few minutes, you wash the excess ink off and then examine the pot closely to see if any crazing is present.

Any pottery that can withstand this test is probably strong enough to last a long time. Nobody that I know of exposes their dinnerware to this kind of treatment, but the test is intended to duplicate the ravages of time in a hurry.

Last night I was testing the newest version of the white glaze on both the newer clay body and the old local clay. Results were slightly mixed, There was no crazing on the pot made from local clay, and no crazing on most of the pot made from the new clay. Where crazing did appear, it was not surprising. The glaze was too thickly applied in that particular spot and had crawled slightly, making that area prone under any circumstances.

There was no crazing at all on the moss agate test. This despite some crawling in the bottom inside.

All of this is very encouraging. More when I have more time.

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