Continuing cracks- large glass! Why?

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Morganica
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Re: Continuing cracks- large glass! Why?

Post by Morganica »

Bonnie Rubinstein wrote:I read this on Bullseye website... in answer to a question posted re: breakage..

" it could be (most probably) that your kiln isn't even in heat across the entire span, making annealing of wide projects impossible.

if this is true, then longer anneal times actually work against you, as they freeze in the temp differences across the span, and only parts of it get annealed, leading to stress. shorter times may possibly work in this case."

so, there is the other viewpoint.
Well, if you read the next post in the thread, the artist has done some fairly rigorous testing of the kiln and how it heats. It heats unevenly on the way up and evens out to within a degree or two on the way down. That's pretty common with glass kilns. Didn't solve the annealing problem, either.

In the pieces that were successful in the past...did you have tacked frit scattered across the piece?
Cynthia Morgan
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Bonnie Rubinstein
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Re: Continuing cracks- large glass! Why?

Post by Bonnie Rubinstein »

Some.

I think the bottom line might be: my thermocouple was the older, exposed tip kind. It was not registering temp correctly anymore. So, earlier fuses worked. Lately, I was annealing too long at a hotter temp than I should have been due to this. Bert did suggest this earlier..and I hope that was it. I can lower the anneal temp, and hold for 2 or 3 hours. Holding too high just stressed the glass.

Thank you, all, really. this has been a long few weeks, and although the U.S. gov't may not be working, I hope my successful fusing does.
Bonnie Rubinstein
Bonnie Rubinstein
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Re: Continuing cracks- large glass! Why?

Post by Bonnie Rubinstein »

Last question…

I will try to repair my broken piece. The crack right up the middle. I will fuse the 2 sides together. Is it better to fuse the crack together uncovered, or cover with a clear piece? I want to disguise the crack as much a possible (not sure I can), and wonder if the crack is more visible when ‘covered’, than not. If direct exposure to the heat will blend it better.

Thank you
Bonnie Rubinstein
Marty
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Re: Continuing cracks- large glass! Why?

Post by Marty »

I wouldn't waste any time on the repair- cut or grind the ragged edges off and end up with 2 good smaller pieces. Then start another large one.
Bonnie Rubinstein
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Re: Continuing cracks- large glass! Why?

Post by Bonnie Rubinstein »

part of my motivation is to see if the new shelf set up and schedule works..then if that piece cracks again, I wouldn't mourn it as much. If a new large piece does crack that I worked on for 10 days, it would be a sad day.

But I do have a question about the idea of cutting an re-using the 2 pieces without re-fusing, as you recommend, Marty.. could they continue to crack in other areas, if I don't re-anneal and 'heal' them?
Bonnie Rubinstein
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