So sorry your piece didn't work out! We suspect that your kiln might be running a little hot, but your temperature might be fine. When slumping into an unfamiliar mold, it is important to check the kiln every 10 minutes or so at the high temperature. You can set the hold for an hour, and if you see that it has slumped after 20 minutes, just skip ahead to the next segment of the cycle.
I think that mnglass's advice is good--- to make a fairly small test tile that is the same style(s) and thickness (6mm?) as your original blank but a smaller diameter (like a 6" square). Try a process temperature of 1225 degrees, and check your kiln at process temperature (which is the highest temperature in your programmed cycle), and at regular intervals until you know how long it takes for the blank to slump all the way into one or more of the indentations. Note how much time the slump took at process temperature, skip ahead, and complete the cycle.
That will give you a starting point for your next try at the full dish, but even on the next try, check the piece before the soak is over to verify that it has slumped enough and is not slumping too much, so you know when to go on to the next segment. After you have done this with the same glass styles a few times, you can program and forget it, but if you change glass colors, it pays to check the slump. I hope these responses are helpful. Let us know if you try it again!
Mary Kay Nitchie
Bullseye Glass Co.
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