kiln casting annealing

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theanimallover
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Location: The Sticks, England, UK

kiln casting annealing

Post by theanimallover »

I did a brief class in casting and have a question...
If using just one sort of glass - one colour billet, is it still possible to have problems after firing? e.g the piece 'pinging' and breaking because of improper annealing? Or does this mainly happen when using incompatible glass.

Thanks.
Brad Walker
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Re: kiln casting annealing

Post by Brad Walker »

Annealing and incompatibility are two totally different kinds of problems. So even if you use a single glass so that incompatibility isn't an issue, you can still have problems with glass cracking and breaking due to improper annealing.
theanimallover
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Joined: Tue Jan 22, 2008 9:19 am
Location: The Sticks, England, UK

Re: kiln casting annealing

Post by theanimallover »

Thanks Brad.
Morganica
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Re: kiln casting annealing

Post by Morganica »

Agree with Brad. If you hear pinging when you open the lid on a casting, it's most often thermal shock.

I anneal for the thickest part of the shortest dimension (which can be difficult to figure out with 3D stuff), and if the casting is more than about 3/4 inch thick I let it sit in the kiln for at least 12 hours before opening the lid. The plaster mold tends to insulate, so even if the plaster is at room temp, the glass inside can still be hot enough to thermal shock.
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