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jpc

Electric Kiln Temp Regulation

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Greetings One and All. Happy Spring! At some point I am sure it will feel like it!

I have been experimenting with my electric kiln with the down firing process. The results have been interesting. My kiln is run manually, I also have access to a programmable electric kiln.  The first issue I have had is getting the temp. the same throughout the kiln. The bottom being cooler than the top which is where the kiln sitter is. The fan is also a top hanger versus a bottom one. I thought the programmable kilns would take care of this issue but it doesn't. With the electric kiln it took so long to get the bottom to temp. my electric bill was ridiculous! There was a thread a while back that discussed how the heat works within the kiln (can not find it) and that it does not work intuitively. Thanks so much!

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There's a lot at play...  With electric kilns and even-ness of temperature, the controller and number of zones/number of elements will make a huge difference. I can't think of what wouldn't be intuitive, though, electric kilns are big toaster ovens...

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do brand new kilns offer even heating? im so fed up with losing work that im ready to give up.

how are you supposed to get an accurate temp when the difference between testing an empty kiln and a full kiln is HUGE?

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The digital controller has nothing to do with the evenness of the temperature if it's a single zone kiln. Whether there is a Sitter with a cone or a single pyrometer, you can have the same problem with areas of the kiln firing hotter since there is only one device that actually senses the temperature. It has no idea what's going on above or below it. The only way to deal with it is to either pack the kiln tighter in the middle so there is more mass there to heat up, thereby hopefully making it cooler in that area, or get a new kiln that has multiple zones, where each section of the kiln fires independently of the others. It's a standard feature on L&L kilns, however most brands offer it as an option.

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My solution to the problem is to try to formulate glazes that look pretty much the same over a span of at least one cone difference. If you are using commercial glazes then you may be able to manipulate them by adding silica, kaolin or fluxes. This will require trial and error but it is worth it in the end. You got to zero in the kiln and the glazes and stay alert towards the end of the run.

 

Plug and play don't make it.

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There is somewhere an very clear explanation of how the heat behaves in the kiln, I believe it is not intuitive. unfortunately I can't find it. The advice I was given was not to use lower portion of the kiln. Not efficient but I tried it with my last firing and the results were good.

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There is somewhere an very clear explanation of how the heat behaves in the kiln, I believe it is not intuitive. unfortunately I can't find it. 

 

For electric kilns from Linda Arbuckle:

 

Heating

There are three ways that heat is transferred in a kiln:

• Convection: air heated rises and air currents circulate heat. This kind of heat transfer happens early in firing. Unless

air circulation is even, the kiln will not be even at this point. Convection promotes more heat at the top of the kiln

and a cooler bottom.

• Conduction: transfer of heat through solids from the outside inward by interaction with molecular structure. Must

be done gradually to maintain even heating. Transfers radiant or convection heat into the ware.

• Radiation: Effective at higher temperatures. Transfer of heat by waves of energy that are absorbed with they meet

cooler objects. Hot objects (ware, kiln furniture, kiln brick) radiate energy in all directions. Radiation helps even out

kiln temperature in still atmospheres.

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