Crack in finished bowl - WarmGlass.com

Crack in finished bowl

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Monika
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Re: Crack in finished bowl

Postby Monika » Fri Dec 14, 2007 1:53 am

Sue,
check your pm,
Monika
Live is a Journey - Not a Destination

Barbara Muth
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Re: Crack in finished bowl

Postby Barbara Muth » Sun Dec 16, 2007 10:32 am

I have seen cracks show up long after firing Lynne. They weren't always clearly compatibility cracks. Sometimes the piece just needs a little stress for the cracks to start. Like the stress of sitting in the sun a few hours a day. The annealing schedule looks okay, but a typical compatibility crack pattern is that of surrounding the offending glass in an attempt to spit it out. This crack appears to be running right through the middle of a color, so unless there is a sliver below of a different color along the fault line, I am guessing that this is not compatibility. However, given that there are other cracks and you have the midlayer of clear, I wonder if your clear glass is tested compatible...

An annealing issue can be fixed by taking the piece carefully up above the annealing temp (and in this case up to re-fuse the piece) and re-annealing using schedules appropriate for the piece. You might want to look in the archives at some of the schedules Lisa Allen started using when she was working with many colors. Her annealing was very conservative and it solved all sorts of problems for her. But if your piece is three layers thick, then your annealing schedule looks okay.

A shame. Looks like a fine design and excellent coldworking from what I can see of the piece. I like clean designs like that.
Barbara
Check out the glass manufacturer's recommended firing schedules...
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Lynne Chappell
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Re: Crack in finished bowl

Postby Lynne Chappell » Mon Dec 17, 2007 1:28 am

You are right, sitting in the sun in a window can start a crack. I have always attributed this to compatibility; as the glass heats up, the differences in the expansion rate starts a crack. It is a strange looking crack, however, very straight, but only felt on the surface not on the bottom, so probably not an impact crack.

I'm thinking though that it is Amazon Green, I had a student with a problem piece with that colour. Very strange, it was a piece with stacked squares of different colours in different orders. Some of the squares had surface cracking that only appeared on the squares that were Amazon Green. But not on every square that had that colour. It defied analysis. And we ran a test on leftover pieces which didn't show that any of the colours were off.

Barbara Muth
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Re: Crack in finished bowl

Postby Barbara Muth » Mon Dec 17, 2007 9:43 am

Lynne, who makes Amazon Green? I assumed this was BE Spring Green and my monitor was a bit dark.
Barbara

Check out the glass manufacturer's recommended firing schedules...

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