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is it possible to candle an Olympic gas kiln?


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Hi,

I've had a number of successful bisque firings with this tin can (size 2827) but haven't been able to stabilize the temperature below 212F to candle overnight.  The peep holes and flue are open.  I've read that some electric kiln users leave the top open.  Would that help?  Any advice appreciated.

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Many folks just pilot to candle. Opening the lid is definitely a way to remove more heat though. I am assuming this is the gas model (Torchbearers)  so as long as things are well vented and open raising the top enough to keep it below 212 seems fine. When we fire our gas kilns, we will candle (pilots only) overnight knowing it will be many hours until It reaches 200. Since these are glaze fires, there is little concern for too much moisture but spending several hours getting there is usually sufficient time for everything to dry slowly. We actually prefer the kiln to be as warm as possible for next days firing.

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8 hours ago, redbourn said:

Thanks, all.  We finally managed to stabilize it at 187-ish with pilot only, open only 1 1/8 turn.  This is good news for us because now we can sleep through the night!

Is there a reason you do not want to exceed 200 in let’s say eight hours?  25 degrees per hour would be considered super slow and usually very safe for drying things out. 187 ish I am assuming is 10-15 degrees per hour Which is extremely slow and safe. Just curious why it needs to end up at 200 or so.

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2 hours ago, redbourn said:

212, and 187 was the closest we could come below that temp.  If 212 were not an issue our lives would be much simpler!

It’s more about rate so in general we always start with warming slowly to approx. 200 to allow any leftover water to vaporize slowly and leave the ware gently. If we go too quickly, then it’s possible a lot of water will turn to stream quickly and break the ware.

A common preheat rate for an automatic controller to dry out ordinary greenware (already dry stuff) is 80 degrees per hour until 250 degrees or about 2-1/4 hours to get there.

Electronic controllers make it possible to go slowly to a preprogrammed temp and then hold for long periods. This is usually only done for very thick, large pieces, maybe sculpture where one wants to ensure the piece is dry throughout and even then only often  see preheat and hold schedules for 6 hours or more.

For normal wares, this is likely excessive and just wastes gas. So getting to 200 in eight hours for ordinary wares should for the most part be very safe as getting to 300 or 400 for that matter. It happens so slowly, that is the key part to removing the water gently. In gas kilns some folks count on the next day temperature to be as high as possible just so they don’t have to fire as long the next day. Candle by pilot is considered by many to do that in a reasonably safe way while slowly drying any remaining moisture.

one exception: I had an engineer / potter present the argument that they did not want to exceed 400 degrees because that was still below the ignition temperature of most paper and textiles. Who could argue against that? I reminded her to remove all flammables including the lawn mower gasoline can from the shed where they kept the kiln. She laughed and said good idea!
 

Edited by Bill Kielb
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25 minutes ago, Bill Kielb said:

one exception: I had an engineer / potter present the argument that they did not want to exceed 400 degrees because that was still below the ignition temperature of most paper and textiles. Who could argue against that? I reminded her to remove all flammables including the lawn mower gasoline can from the shed where they kept the kiln. She laughed and said good idea!
 

:rolleyes: Perhaps she had neverboiled water for tea on the stove and watched the steam come out of the spout of the kettle. It's not the paper burning, it's the water exploding.

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