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Kiln Over Fired , First Time Using A Kiln


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I have an old Scutt kiln with a kiln sitter that I just repaired with new elements and replaced 7 bricks. Did a test fire with only shelves and witness cones in it. Checked on the cones a few times and the last time I could not see them, I realized  they all are flat I shut down the kiln. I let it cool down a bit and peeked inside to see the witness cones are puddles. I will have to figure out why the kiln sitter did not shut off at 04 like it should have. I am guessing that with the cones having melted so bat that it was WAY over fired. 

The sitter did not release for some reason. I had it adjusted correctly with the gauge but I might have to adjust the release bar down and try again. Also will try to move the sitter cone over a bit to the thinner side. Another thought might be to get some 02 cones and see it it will fire to 04.

The sitter will shut down if I do not have a cone in it, maybe I have it adjusted to close.

Don't want to try any pots in it until I can get it closer to the temperature shutdown point.

 

Any ideas what else to look for?

 

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I'll let Neil, and the other more knowledgeable folk here offer solutions. But, quick question, does your kiln have a shut off timer too? Those come in handy, to avoid over firing, especially once you have wares in there.

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I was running  a test fire with no pots in it, just shelves. I had the elements on high and in 3 hours cones 03,04 and 05 are puddles on the shelf. At least I know the new elements work.

Yes I also had a timer on but had it set to about 6 hours as it was a test fire and did not know how long it would take to reach cone 04

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I had a 04 in the sitter. I am checking the settings again on the sitter now that the kiln has cooled down. 

I guess I should have used kiln wash in the witness cone stand, I can not remove the cones...

Does it matter the direction of the number stamp when placed on the sitter? Does the stamp have to face down?

I hope to try another test tonight and see if I have better results .

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I may have found the issue. I had the sitter adjusted just a little to tight. It would drop the weight when the gauge is in place but it would rip the catch. 

I adjusted the catch and also moved the sitter cone over a little to have it drop sooner.

Hope this works.

 

How often after the kiln is hot should I check the witness cones to see if they are bending over?

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I have a few thoughts-make sure you are using the junior cones right?

place cone so rod is in middle-I never pay attention to where the numbers are. Also my supports are not washed but that is a good idea.

Next fire use a large cone (same cone # as the junior sitter cone) on the middle peep on same level as sited so you can see it and know what temp it is fired to. 

You will have to pay attention to this next fire so you can turn it off if its getting away from you. A digital pyrometer is also a great idea so you know small changes.

Mark

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Do you have the setter template that allows you to adjust the weight on the shutoff lever. If not, just set to lever to drop on a hair trigger. i.e. have the catch set at a minimum hold. Are you using bars or cones. bars are simple. Cones set on the high ridge , slightly different from the two other ridges.Coat the bar and cone support with kiln wash.

 

Marcia

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I have the template and readjusted the shutoff lever, I had it set to tight. The lever would drop but when set on the gauge it would touch the catch.

I am using cones, the supplier that is closest did not have bars.

I set the cone a little cooler and ran a test  again with just shelves in the kiln .Started on low for 20 min then went to high and checked every 15 min. 2 ¼ hours later the Kiln shut down with the witness cones looking just right.   

Was a little worried after the first fire, never run a kiln and I just rebuilt this one.

 

Now if I can figure out how to jet the melted cones out of the base .I used kiln wash on the next one and expect I can remove them tomorrow.

Any ideas how to get the melted ones out? What if I put them back in the kiln suspended upside down?

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What model, voltage and phase is the kiln? 2 1/2 hours is really fast, even for a small kiln.

 

Small cones should be placed in the sitter with the little number facing the interior of the kiln. The rod will be sitting on the spine of the triangle.

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The Kiln is a Skut 231 with 3 rings, 240 volt 1125 watt with new elements. I ran on low for ½ hour then high for 2 ½ before the sitter shut off. This was only a test fire with no pots inside only shelves. The test last night worked well and plan to try my first bisque fire today on a nice slow schedule.

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Any ideas how to get the melted ones out? What if I put them back in the kiln suspended upside down?

 

You could try drilling them out.  It's what I had to do when our kiln over-fired.  It was cheaper tho' to buy new stands than spend the time and break the drill bits lol.

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Don't waste time and effort trying to remove melted cones from a plaque.  Learn how to make your own cone packs, that way you will have a lifetime supply costing next to nothing.

 

Make a 1/2" diameter coil of clay about 4" long.  Press your thumb or similar into one end to create a small "bowl" on one end of the coil.  This is where the lowest number (coolest and melting first) cone should go.  Press the next 2 cones into the clay in a line right behind the first.  Press them just about all the way through the coil so the bottom angle is correct and flush with the table top or whatever horizontal surface you are working on.  Pinch the clay around the bases of the three cones to hold them in place and take your needle tool and start poking holes.  Make sure you pay attention to the thicker parts between the cones and edges.  Make it look like swiss cheese- more holes is better.

 

Using this method, I have never had a cone pack explode or even crack.  You can put the unfired cone pack in with a bisque or glaze load without worries.  When I do this, I usually make a bunch just to have on hand ready to use.

 

Good luck with your new toy!

 

Rob

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If I whoop my kiln up very fast, it affects the drop of the sitter, in fact the cone seems to melt onto the supports even with kiln wash and it does not drop.

Don't know the explanation of this material wise, just observed this.  SO I'd be expecting a sitter failure if I place mine on high for 3hrs. . Fired at a"normal' rate the sitter and cone behave normally, still have timer and log book in hand as it were.

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The Kiln is a Skut 231 with 3 rings, 220 volt 1125 watt with new elements. I ran on low for ½ hour then high for 2 ½ before the sitter shut off. This was only a test fire with no pots inside only shelves. The test last night worked well and plan to try my first bisque fire today on a nice slow schedule.

 

Not 220 volts. It's either 208 volts or 240 volts. Does the serial plate say 220V?

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