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Each time I have tried to make a plate or platter with my 90 coe glass I end up with some kind of problem. So I tried using 96 coe and it seems to work better for me. I honestly do not know why but I am going with it. Making pendant pieces 1 to 2 inches with 90 coe is fine. I may have a bubble here and there but no breaking problems. The attached picture is a plate I make with lots of left over pieces. I used a 9.75" square of clear and spread out the misc pieces. Almost all if it had not been fired before. I did add in some pieces left over from trimming pendants. I am positive all the glass is 90 coe. The edges were uneven so I decided to go with it and added in more curves with the grinder. I slumped it in a shallow square plate mold. Looked great when I took it out. I was washing it and it broke. I can also see another curving crack that's about 2 inches long that is almost touching the edge. So I expect it to break again. Can anyone tell me what is going on? It is so disappointing.

Thanks, K

ps. Should I try to refire it and repair the break? Somethings I have fired several times and have finally given up. I will break them up and use the glass in mosaics.

Was the glass completely cooled before you washed it, or was it still warm? What was your firing schedule?

strange things can happen to different glass when it is re-fired several times. It also appears that due to the differences in thickness of the piece that the annealing may have not been sufficient for this slump and how much area of the slumped piece touched the mold. That could cause uneven heating and cooling depending upon the mold. Just because it is all the same COE doesn't always mean it will remain that way. Some glasses actually change COE every time they are reheated and this can cause lots of problems It appears that you have many different colors of glass in that piece and the more you put together the greater chance that problems can arise. Some of those glasses are more fluid than others and that can also affect the compatability of the overall pieces.
Lots of variables using so many colors that it makes the output of a successful piece difficult.

Yes, more info please. That crack looks a lot like thermal shock (they're usually meandering with a bit of a hook/direction change in one end). If that's what it is, the brand of glass isn't as important as other factors.

So...per GlassFever, WHEN did you wash the glass? Right out of the kiln or did it sit for a couple of hours first, and cool down?
How thick is this piece?
What was the firing schedule?
What colors were refired (i.e., from your pendants)? Hot colors tend to be more sensitive to compatibility shifts than cooler colors.

We should have a pool before Kelly posts her schedule. I'll put 1 magless on bad annealing.

Marty wrote:We should have a pool before Kelly posts her schedule. I'll put 1 magless on bad annealing.

I'll see your magless and put another on ramping up too quickly.

Here's my firing schedule:
1 400d/hr to 1250 hold 30min
2 600d/hr to 1480 hold 10min
3 AFAP to 900 hold 40min
4 150d/hr to 700 off

The majority of the reused pieces were dichro on black, a few on red glass. They were scattered across the plate in no particular pattern. The plate ended up being just under 1/4 of an inch. It was also room temperature when I washed it. It had been cooled off for several hours. I think I got all the questions answered. Who won the bet?

Thanks so much.

Valerie- it's a draw.
Kelly- slow down on the way up and anneal for longer. Follow BE's schedules with attention to "special" circumstances like unequal thicknesses.

Do you think I could full fuse again to put it back together and slump it once more?

Yeah probably, but your time would be better served making something that required thought and design. You're certainly not the first person to make somethig like this, but I've never seen a good one.

Kelly, I like what you are creating and as Marty says, try to slow down. Also you could think of taking some of the scrape pieces and layer and slice up , to make a new design feature with the pieces. Bullseye has a true firing schedule system that works , and I usually will even add more time so that it has every advantage of working. Good luck and enjoy your glass journey. Les