Hi, this is my first post to the board, but I have been lurking around for a while. I checked and didn't see the answer to my question ... I apologize if it has been asked before.
I am in a bit of a crunch for Christmas. Usually, I fire and allow the kiln to cool down overnight (which means I can get a maximum of one firing in a day). I read that once you get down to 750, that if you have a 12" diameter, 1/4" thick piece, you can cool the rest of the way to room temperature in 80 minutes. My kiln takes WAAAY longer than that (probably 6-7 hours).
Is there some way I can speed up the cooling process? I can pull out one of the peep-hole blocks, or put a small wedge in at the top to allow air in. However, I don't want to risk thermal shock (since I'm ALREADY behind for Christmas), but I'd like to try to get 2 firings in a day.
Any suggestions or advice would be GREATLY appreciated!
Thanks again.
Cooling rate below 750 degrees
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Geri Comstock
- Posts: 340
- Joined: Mon Mar 10, 2003 4:16 pm
- Location: Northern CA
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Alot of speeding up cooling rates in your particular kiln takes experimentation to understand your particular kiln and it's limitations. Mine is a top loader, which helps in this process immensely. I also live in CA and my kiln is in my garage. Temps out there rarely get below 60F and there's no drafts near my kiln.
The first thing is that you shouldn't open the kiln before it gets below about 700...if you've using BE, the glass in it has to be below 740 to be below the strain point. A 700 pyrometer reading gives you a little extra margin for error since the glass could be hotter than the pyrometer reads.
My kiln is very deep...18" and my shelves are at about 14". I'll tell you how I cool things faster in my kiln, but it may not work for yours unless it's really deep. Mine is deep enough that the glass won't thermal shock from cold air getting to it.
At 700F, I crack one side of the lid about 2 inches with a short kiln post. At 600, I crack that same side lid about 4 inches. At 400, I open the lid about 5-6 inches. At 250, I can open the lid completely so it cools from there pretty rapidly.
I wouldn't use this strategy with a shallower kiln because of the risk of thermal shock. It took me alot of mistakes to figure out just how far I could push cooling with my particular kiln.
Alot of it depends on how close the glass is to the lid. The more space between the glass and the top of the kiln, the less risk of thermal shock. I'd also never use this if I was slumping something deep because of the risk of temperature variations and then thermal shock.
So, the short answer to your question is that yes, you may be able to speed up cooling. But the risk is that if you speed it up too much, it may thermal shock. Experimentation is the only way to know for sure.
Good luck!
Geri
The first thing is that you shouldn't open the kiln before it gets below about 700...if you've using BE, the glass in it has to be below 740 to be below the strain point. A 700 pyrometer reading gives you a little extra margin for error since the glass could be hotter than the pyrometer reads.
My kiln is very deep...18" and my shelves are at about 14". I'll tell you how I cool things faster in my kiln, but it may not work for yours unless it's really deep. Mine is deep enough that the glass won't thermal shock from cold air getting to it.
At 700F, I crack one side of the lid about 2 inches with a short kiln post. At 600, I crack that same side lid about 4 inches. At 400, I open the lid about 5-6 inches. At 250, I can open the lid completely so it cools from there pretty rapidly.
I wouldn't use this strategy with a shallower kiln because of the risk of thermal shock. It took me alot of mistakes to figure out just how far I could push cooling with my particular kiln.
Alot of it depends on how close the glass is to the lid. The more space between the glass and the top of the kiln, the less risk of thermal shock. I'd also never use this if I was slumping something deep because of the risk of temperature variations and then thermal shock.
So, the short answer to your question is that yes, you may be able to speed up cooling. But the risk is that if you speed it up too much, it may thermal shock. Experimentation is the only way to know for sure.
Good luck!
Geri