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Old 03-15-2018, 08:54 PM
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Kiln tranfering heat down - how to stop?

I have a Paragon fiberfuse 16 in my classroom. The counters in my art room are all fire proof - the heavy black type that would also be used in a chemistry lab - not stone, but some other man made material. I have fired the kiln once and it made the counter top very hot. I was still able to touch it with my glass blowers hands...but the temp has me worried - pyrolysis to the wooden counter base. What can I do to insulate the kiln from the counter top? The kiln comes factory with riser legs and rubber feet. If I set it on a layer of thin fire brick or kiln shelves, it will still radiate heat out to all of that potential thermal mass and still transfer the heat into the counter below it.....
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Old 03-15-2018, 09:05 PM
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If the countertop is truly the same as a chemistry lab then it is likely to be soapstone and very tolerant of high temperature. The wood underneath would be the only concern. As you indicated.
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Old 03-15-2018, 09:46 PM
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Multiple dead air spaces, try two or three, then stick a probe in there at the bottom. If it's over 135F, it's still too hot.
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Old 03-16-2018, 07:45 AM
Rosanna Gusler Rosanna Gusler is offline
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Concrete blocks laid on their side make a nice kiln stand. You can store props and stuff in the holes.
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Old 03-16-2018, 12:08 PM
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Dead air spaces

Pete - any recommendation on the minimum height for a unit of "dead air space"? I am thinking about using sheets of thin concrete backer board.
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Old 03-16-2018, 02:42 PM
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Make each one an inch, use two. Then feel it out. A lot depends on the firing cycle. If it's continuous it needs more. Aluminum foil on the top one will really help.
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Old 03-16-2018, 02:52 PM
Art Freas Art Freas is offline
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I think you are fusing, so if you have 1/4 fiber paper maybe a layer of that under the foil on the top layer. That gives an immediate air layer under the foil limiting the conduction to the feet.
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Old 03-16-2018, 04:40 PM
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Thank you for the suggestions. I am guessing shiny side up on the foil to reflect the most heat?
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Old 03-16-2018, 05:40 PM
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I might try a couple metal 2x4 studs cut to length and lie them flat. That should provide adequate air space and suport the kiln evenly. Whatever you use its going to be the air space that stops the heat transfer.
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Old 03-16-2018, 07:45 PM
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Brian, just run the thing and monitor what it really does in real time. Then do the corrections, monitor them. Pyrolisis is a slow motion machine based in ambient temps. My take in all the fires I 've looked at is 135F is as high as you want it to get if it's continuous. Other wise, you have to look at the materials.

I'm basing my findings on Weinberg, Chiarizia, Bissett, Keckic and my own studio and bathroom ( which never lit off) and a number of pottery fires which had pyrolitic deterioration along with my dear departed mentor Tom Langhorst's observations from the New Mexico State Fire Marshal's office at whose feet I studied the issue. He taught me to look and think. Rare in the arts. RIP Tom. I miss your wit in the night.

Tom and I were working a fire one night in the south county and we were running the sniffer and there was another guy from the Fire Marshal's office who really wanted to go home.It was around 2:00AM. We didn't like him much as we kicked the crap around just looking and mumbling. Dave asked Tom to tell him the cause and origin which is what we always want to know in an insurance case. We look at checks in the wood, both large and small and follow them. Little check are near the inception, big ones, it's ripping. Tom said "Residual Electricity" . Dave wrote it down and left. We were there another four hours. Dave got fired the next day.
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Old 03-16-2018, 08:54 PM
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"Residual Electricity"? That's a new one, up there with Douglas Adams' structural exasperation.
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Old 03-17-2018, 09:11 AM
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well maybe in an undischarged capacitor but you don't find them in mobile homes.
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Old 03-17-2018, 11:03 AM
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Well... if you have let the national enquirer catch your eye in the check out lane at the grocery store, people can just spontaneously combust while chillaxing in their lazy boy recliner... so anything is possible.
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Old 03-17-2018, 12:11 PM
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You'll want to install a phlogiston suppressor, too.
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Old 03-17-2018, 01:35 PM
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you can't suppress phlogiston. That was the entire point.
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Old 03-24-2018, 07:53 AM
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Here is the kiln base that I came up with - old wall shelf hangers cut to length with a thin piece of hardie backer board attached. The single air space worked at maximum temperature (1500F). Between kiln and hardie board it was 140F - between base and table top it was 115F.
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Old 03-26-2018, 12:42 AM
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Concept is good, but find something other than the hardieboard. 140 is too hot for that board.
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Old 03-26-2018, 09:18 AM
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Quote:
Originally Posted by Art Freas View Post
Concept is good, but find something other than the hardieboard. 140 is too hot for that board.
You might be thinking of some other type of board. Hardie board is cement board. It Will not burn and is well known for using it these type of aplacations. The caveat I see is the free silica the board is made from can be a respiratory hazard. Undisturbed I would think it's just fine.
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Old 03-26-2018, 10:04 AM
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I have used Hardiboard as the outside of a rectangular gloryhole. It lasted ten years and although it did eventually crack, it was never an issue. It's not an insulator but I don't think it's any significant hazard. 115F on the tabletop is not a risk in my mind. Keep in mind it's also periodic.
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Old 03-26-2018, 11:22 AM
Cecil McKenzie Cecil McKenzie is offline
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1 inch of ceramic fiber equals something like 18 inches of hard brick. Put fiber of table top and metal studs flat on top of that.
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Old 03-26-2018, 12:50 PM
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While that's true, it is far more effective at higher performance temperatures than it is in the range Brain is using. Also, it is still obnoxious about fiber release. Brian has lowered the temperature at the hot face of the table to a very reasonable level. That was the goal.
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