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Crazing is one of the most common glaze defects. At temperature, the clay body and glaze fit perfectly however, upon cooling the glaze is under tension. The glaze contracts more than the clay body.
There are several methods to correct crazing. Often potters do not realize the clay body is not vitrified enough causing the glaze not to fit. Make sure you are firing the kiln long enough to glaze maturity as fast firing can make the clay less vitreous.
If the craze lines are tightly spaced 1/4" or less (think road map of Manhattan) reducing some of the materials that cause crazing will help such as feldspar's which have a high thermal expansion with low expansion materials such as flint or zinc. A glaze calculation program will help with bringing the glaze into a compatible range with the clay body. Delayed crazing can happen days, months or years latter.
If the craze lines are far apart more than 3/4" (think road map of Alaska) additional increments of flint 325 mesh or 400 mesh can move the craze lines to a greater degree apart and then disappear. Most glazes have room for slight additions of flint without changing their color, opacity, or surface texture.
Crazing can occur if the pot is under fired or over fired both situations cause the glaze not to fit the clay body.
Crazed pots are 10 times weaker than non crazed pots.
Glaze crazing a fine network of lines in the fired glaze.
The glaze on the left is not the right one minus silica.
Gemini generated image showing state of the art in May 2026. The prompt was "Two pottery mugs, one is crazed. Both are made by the same potter and are the same shape and size. Both have a transparent glaze and underglaze prairie motif brushwork."
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