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Craig Kitzman

Uneven temperature Minnesota flat topkiln

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Since the forced air burners (usually two) are on bottom that is where the heat is generated . I suggest making the target bricks angle some flow upwards.-also  stack the bottom tighter and looser on top to encourage heat to flow into top and slow it before it can exit Bottom with that part tighter.

I feel any kiln that size with only two burners is asking for hot spots.

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Not 100% about this but I'm not sure a true Minnesota flattop has bag walls. If so raising them will work fine.If the kiln has none try the directing target brick to shoot that flame upwards at a angle .

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I have the same issue with my flat top downdraft. Hot down by the burners, cooler on  the top shelves by at least a cone.

I'm finding that besides fiddling with the flue and blower flaps/gas, when it gets close to desired temp, I'll cut the gas down 1/3rd and adjust flaps for optimal flame and let it stabilize (essentially soak).  Turning down the gas (hot burners) tends to even out the temp top to bottom and still reach the target temp.

Hope that helps.

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J.T. Abernathy in MI had burners half way up the kiln also.  His theory was put the heat where you need it.  Supposedly a 30% decrease in fuel usage as opposed to similar kiln - actually as compared to Marc Ward's numbers.  Would be interesting to see one with and one without and see the difference. Hmmm. I feel an empirical data collection moment coming on...  If you added a burner up half way up, theoretically it would only have to increase the cost of firing by the additional electricity to run the blower.  Making an additional burner would be in initial outlay, but if it cut costs, just a matter of time for break-even and then savings. ... Just brainstorming for ya.

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Part of the problem in many of the gas kilns is that the exit hole is too big.  Another is that the stacking does not allow the gases to circulate within the kiln.  The burners should be causing the gas inside the kiln to circulate.    Of all the kiln books I have examined (10+ I think) only Mel Jacobson's "21st Century Kilns" has addressed the circulation issue.  Nils Lou's book hinted at the problem and did identify the oversized exit hole as being a cause of both wasted fuel and poor temperature uniformity.  

LT

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I assumed that his kiln has the original liquefied (propane )power burners. Those really had great output and turbulence . Lets see if he is still here for an answer 

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More information on cold top in Minnesota flat top: 2 sk 1ss liquified propane burners at 3lbs at regulator. Hot on top by a cone or two until cone 1 then abruptly switches to hot on the bottom as indicated. I've moved target brick toward burner incrementally but this also exacerbates the hot top during early stages .

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For me I could care less about cone 1 temps going to cone 10.I need more eveness at cone 8 or 9 before 10.  Early hot tops make sense as thats where the heart goes before kiln starts to breath.

There has been a lot written on flat tops-lois book and Mel Jacobson if I recall as well. I'm suggesting an angle to the target brick not closer to direct heat up near the top end of temp when the glaze is melting.

This kiln has no bags walls right?

Mark

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