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Help with crazing and underglaze flaw

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Hi Everyone,

I am having two different problems. First I am encountering crazing about a month after I take pieces out of the kiln. The second problem I am encountering on other pieces is that painted designs become bump after they are glazed. The glaze and the paint are both Duncan brand. Please help.

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The crazing is most likely due to enough of a coefficient of expansion difference between your glaze and Claybody.. That it is delayed indicates they are likely close but enough of a mismatch that it eventually crazes. Lots of ways to try to fix crazing so I expect you will have lots of questions to answer. As always pictures here help folks a lot in being able to respond.

The underglaze and glaze issue often is the result of heavy underglaze application and certain colors of it being a bit more refractory than the overglaze will melt.

As long as the underglaze is not fired beyond its range we have had success using our own mixed clear glaze with a bit more boron added to melt over some of the tougher colors. This may or may not be something you want to pursue.

If what I described is your issue, I would ask if you have less problems over watercolor (thin) type applications and whether there are any particular colors that are worse than others with the bubbling.

Edited by Bill Kielb

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