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Old 08-26-2018, 01:57 PM
Chris Lowry Chris Lowry is online now
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Compatibility question

Can an annealing issue cause compatibility issues?

My wife fuses together cane that we make in the hot shop. She just made a large piece that got some tinny cracks only on R306. They showed up after grinding.

It is a color that she has used many times with no known issues. We still have a piece that is a year old with the color and no cracks.

This piece was fired in a new kiln, so the question is did the kiln cause the problem?

Other differences were that this is the largest piece she has ever made, although the same thickness. It’s a different kiln shelf. Same clear glass but maybe it had been in the furnace for a while.

Since only that color is showing signs of cracking I don’t see how it could be the kiln or the schedule.

What do you think?
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Old 08-26-2018, 02:23 PM
Eben Horton Eben Horton is online now
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If you only sawed this piece, the color is probably incomparable in the other pieces as well. Sawing brings out the glass’s “true colors”
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Old 08-26-2018, 02:36 PM
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Pete VanderLaan Pete VanderLaan is offline
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I think we should exclusively call this "Incomparable" from now on.

Just because a piece doesn't break up when you first make it, doesn't mean it fits. When you saw or grind, you break the surface tension of the glass in question. I had a piece in Santa Fe we all knew would explode if it was ever ground. It sat on the shelf for ten years. Just before we shut the shop down making the big move east, I called staff and we did what we had talked about for years and I touched the piece down on the 60 machine. It blew violently.

It is the case that bad annealing is frequently blamed for mismatch but if you don't do basic testing rather than assumption, you will periodically be in a world of hurt. If you took any of the Kugler Opaques and put them with a true 96 glass and ground them, they will all break. Many other colors fail as well. Sometimes it may take a week or so to let go, but it's going to let go. Sometimes it just puts your eye out.

"Incomparable", That's great. I love Eben's spellcheck.
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Old 08-26-2018, 02:43 PM
Chris Lowry Chris Lowry is online now
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All her pieces get the same amount of grinding and are made in the exact way.

So you say it can only be incompatibility?

My guess too.
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Old 08-26-2018, 04:11 PM
Eben Horton Eben Horton is online now
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argh.. I am loosing my vision. INCOMPATIBLE !!!
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Old 08-26-2018, 06:24 PM
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I would never assume " So, it can't be this". The color may have changed in batches. Temperatures are measurements of microvolts, size is always a factor.

You have to test.
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Old 08-27-2018, 11:53 AM
Brendan Miller Brendan Miller is offline
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I will throw 2 cents in here. I think what you have found is that larger work has a smaller margin for error.

You can "get away" with only so much in the compatibility range depending on the dynamic you setup in the material.

Annealing correctly can give you the best chance for the material, but if the color is truly incompatible than it should never survive cold working, small or large. Knowing your kiln can allow for you to correctly anneal. Hot spots, cold spots, the shelf position, the shelf itself, having space below the shelf...ect. There are ways to test your kiln to know whats happening inside.

If you are using different colors combinations, they can become incompatible from being on separate ends of the tolerable spectrum.

In the end what your probably seeing is that your glass is not annealed as well as the smaller pieces for whatever reason and the canary in the coal mine is the color. Or the color was never compatible and you've been getting away with it because it was in a more perfectly produced material. Test and know.
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Old 08-27-2018, 12:57 PM
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Make the same pieces in clear. Treat them identically. Change nothing. Then use a very good polarimeter to look them over.
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Old 08-27-2018, 03:46 PM
Jordan Kube Jordan Kube is offline
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I think about blowing and casting/fusing as two completely different animals when it comes to compatibility. Casting/fusing is way less forgiving of mismatch.
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