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nancysmith

Test firing electric kiln

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I have a small electric kiln that I've test fired.  I'm very new firing kilns....

Cone 6 in the ASD

Cones 5,6 and 7 for witness cones.  One set on the bottom shelf in front of the peephole and the other set on the top shelf in front of the peephole.

Safety timer switch turned to 20

Switch set for high fire

Kiln turned on, the ASD cone 6 tripped it off, the safety timer switch had 1 hour left on  the dial

Kiln turned off and cooled 

After opening the kiln (it was an empty kiln because I was test firing) the top set of witness cones were fine, cone 5 overtired, cone 6 good, cone 7 underfired.  The bottom set of witness cones only turned white and standing straight, no bend at all???? 

Why would this be?  Something I did wrong?  

Nanc

 

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Were the cones placed directly on the floor of the kiln? This would explain why the bottom cones are underfired. The floor of the kiln is difficult to heat, because the floor is a heavy thermal mass that requires a lot more energy to heat than the center of the kiln.

Arnold Howard

ahoward@paragonweb.com

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5 hours ago, Arnold Howard said:

Were the cones placed directly on the floor of the kiln? This would explain why the bottom cones are underfired. The floor of the kiln is difficult to heat, because the floor is a heavy thermal mass that requires a lot more energy to heat than the center of the kiln.

Arnold Howard

ahoward@paragonweb.com

The cones were on the bottom shelf about 1" off the bottom base of the kiln

So when the kiln is full of pieces to fire, what happens to the ones on the bottom shelf, compared to those in the middle and top??

Edited by nancysmith

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@nancysmith I'm wondering if all your elements are working. A small kiln like that should have plenty of power. Turn it on high for a few minutes and see if all the elements glow. Just carefully crack the lid and take a peek inside with the room lights off. Also check the serial plate and see what the max temp is. Could be that you're maxing it out, and the elements are a little worn so it's having a hard time getting to temp. A kiln that's rated for cone 6 really isn't good for firing to cone 6.

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5 hours ago, nancysmith said:

I will check the elements for sure!! 

When you say a cone 6 kiln doesn't fire to cone 6....because this is so new to me....will I be firing to cone 5? And using cone 6 clay?

 

I mean that a kiln will only get to its peak working temperature if the elements are in perfect condition. As soon as they age a little bit, they don't have the power to get there any more. Ideally you want to fire 3-4 cones below the peak temp. That way the elements can wear a while before they need to be replaced. It's the difference between getting only 50 firings out of a set of elements instead of 150.

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I just turned on the kiln for a few minutes, cracked the lid and all elements were red.  The max temp is 2300.

Also there's an automatic dial which I used for my test fires, or manual low and manual high.

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Kiln fire differently with no load in them. You need the thermal mass to find out how it really will work .

I read your kiln specs online and it should do cone 6 as its rated to cone 8.

19 hours is way to long for a fire.

I suggest firing a real load of pots and put cone all over to see whats going on.

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If it won't reach temp empty, it won't do it full either, and you run the risk of ruining a lot of glaze work. No sense loading it up with work until you know for sure it works. Try another cone 6 on manual high and see if it does any better. It could be that the automatic setting it ramping it up too slowly.

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