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heat treating

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JoJoDapyro:
With my very limited heat treating, I have found more of an issue with Cooling fast than that of getting it to temp too fast. I lose more stone on the cooling end, than I do the heating end. So what I take from it is that my kiln heats slowly, and cools more quickly. This weekend I'll see what it heats to, I have only ever used one element of the two in it.

iowabow:
If you don't have digital temp control you could put some additional mass in the kiln.

JoJoDapyro:
I normally fill it. It is strange that it breaks while cooling. I normally have to wait 48 hours after it is off to be able to handle the stone. I don't ramp down, but the kiln is efficient enough that the cooling time is far longer than the ramp time.

Chippintuff:
I only have a little experience at melting glass. There are definitely big differences between various glass that is out there, bottles, windows, cookware and even paper weights. The melting points and annealing points of them varies widely. I never had any luck with mixing one batch of glass with another, and I think it was because their reaction to heating and cooling varies widely. All the glass that I worked required temps much higher than 900 F to melt. Maybe he was talking about Celsius. Heating in a hurry never seemed to cause a problem, but cooling fast did. My best results were obtained when I slowly cooled to 800-900 F, then held it there for a couple hours, then continued the slow cooling. The time spent at the annealing temp was critical to their "temper". Some that I held there for longer annealed so hard that I could not knap it.

WA

JoJoDapyro:
It was Celcius, about 1700 Fahrenheit.
I am strictly talking about stone.

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