Electric Mid&Hi Fired Ceramics
Potters & Sculptors - Making Rock from Mud
glaze cracks and peels off the pot
A clear glaze that I have used for years crackled badly so much so that it can be lifted off the pots. Ther was a slip underneath that was fired in during bisque. On top of the slip was underglaze. Anyone any idea? The glaze also underfired.
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Replies to This Discussion
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Permalink Reply by Joseph Bruce Jordan on
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it might be a silly question on my part but was the underglaze fired before putting on the glaze? Also did the glaze peel from all over the pot or just over the slip or underglaze?
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Permalink Reply by Annika Hinze on
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No, it was not fired in. If fired in the color is much stronger and when glazed without firing in it is more pastel, which is what I was looking for. I have done either before without ever having problems. The glaze peeled from all over. I am suspecting that clear glaze bucket - the green and blue liner glazes used on some did not crack. This is the downside of using glazes in a collective - you never know what someone else did to it before. [Note to self: always use your own glazes]
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Permalink Reply by Norm Stuart on
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One of the problems with bucket glazes is convincing people to be certain that they're completely mixed.
When a bucket of glaze has an inch of solids at the bottom, you're missing most of some of the glaze ingredients.
So what you're applying is not actually a glaze.
People tell me they like bucket glazes but few are willing to actually put their hand in to feel if any has settled out.
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I have a glaze that is usually very well behaved but the last time I made a batch it started cracking and flaking off the pot. I can still use it but now need to apply and fire, reapply - particularly in the bare patches and refire. After the second fire it's great but I'm going to make a new batch and calcine some of the clay in the glaze to hopefully give less shrinkage. This glaze is a wonderful bronze that's pretty important in my work so I don't want to abandon it. Something that can help too is 1-2% CMC Gum in the glaze. If it was a glaze you make yourself I think Insight can help with re-formulating the glaze; this is the route I think I'm going to go with my bronze if calcining doesn't work.
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Any chance that you erred when mixing the glaze? Put in a wrong ingredient or twice of an ingredient or such? It's pretty easy to do, and might not be noticed. I'd be tempted to mix up a small batch, being very careful, and testing it to see if it behaved.
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