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These are Amaco bottled glazes, a transparent and a decorative on a porcelain at cone 6. The glaze fit is poor, severely weakening the piece. I tapped this lightly with a spoon about 2 cm below the rim. It sounded like I was hitting a wet sack of rocks! And the handle fell off! Another few taps and the piece broke like auto-glass. This type of functional ware is entirely unacceptable. The IWCT test, which anyone can do, can help assess the risk.
If you buy commercial bottled brushing glazes then there is nothing you can do to adjust the recipe. When they fit a clay body (without crazing) it is just by accident (since the clay body and glaze manufacturer do not cooperate to ensure fit). Unfortunately, it is common for them to craze.
| Troubles |
Glaze Crazing
Ask the right questions to analyse the real cause of glaze crazing. Do not just treat the symptoms, the real cause is thermal expansion mismatch with the body. |
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