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Nabertherm kiln fired bisque twice


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I fired my recently acquired 2nd hand but only 6 month old kiln yesterday for the first time.  I didn’t expect an issue. Set the bisque to fire to 980c. Started at 7pm. Checked at 7-8am, it appeared ok and cooling down. Temp around 780c. Busy day. Went out in the morning. Checked it at 2pm and temp was going back up. So I thought maybe I misread the temp in the morning as I was tired. Anyway as I wasn’t 100% sure if there was an issue, I let it carry on. Assuming if it hadn’t got up to temp it would do so now . I made a quiver spreadsheet to check ramp or hr and temp and realised it wasn’t right. But thought well damage done. It will cool down now. Had to pop out for an hour. Husband came home and sud it was going up again. So at this point I turned it off to stop the program. No witness cones. 

i have 2 questions

1) will my bisque wear be any good. Will it take glaze? 

I had a lot of test tiles in, should I chuck them out?

2) does this sound like a fault with the kiln or in the program. I created a new program.

thanks.

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No cones? no way to tell other than ringing and feeling bisque ware to see if its overtired . If it is then the stuff will be really hard to glaze-and I suggest  tossing it out and starting over. Yes with a new program and cones and stay with kiln to see whats going on. 

I answered below as well.

4 hours ago, Clayfox said:

I fired my recently acquired 2nd hand but only 6 month old kiln yesterday for the first time.  I didn’t expect an issue. Set the bisque to fire to 980c. Started at 7pm. Checked at 7-8am, it appeared ok and cooling down. Temp around 780c. Busy day. Went out in the morning. Checked it at 2pm and temp was going back up. So I thought maybe I misread the temp in the morning as I was tired. Anyway as I wasn’t 100% sure if there was an issue, I let it carry on. Assuming if it hadn’t got up to temp it would do so now . I made a quiver spreadsheet to check ramp or hr and temp and realised it wasn’t right. But thought well damage done. It will cool down now. Had to pop out for an hour. Husband came home and sud it was going up again. So at this point I turned it off to stop the program. No witness cones. 

i have 2 questions

1) will my bisque wear be any good. Will it take glaze? 

You will have to see how hot it got before we can answer this-see above to tell.

I had a lot of test tiles in, should I chuck them out?

Yes start over with new tiles-as these will not glaze right.

2) does this sound like a fault with the kiln or in the program. I created a new program.

My guess is the program

thanks.

 

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Thanks for the reply.

kiln not yet been opened. It’s saying it’s 130c. So I should wait a bit more.

i managed to get the firing info. I know what happened now.

the repeat function got caught when checking the program. I didn’t think it had saved that but it had.

so it did the full firing from 0 -980 once

at that point, I saw it in the morning cooling down and assumed all was well.

it cooled down to 600bat which point the repeat function started. It did the 600-980 three times in all before we realised and shut it down.

human error.

so best to chuck all out?

i am tempted to glaze a few pieces and run them through. If they are messed up, doesn’t matter.

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No I wouldn’t chuck things.  I would use it to learn.  Pottery can be fired multiple times. Some sculptors depend on the feature.  

I could do the flinck with finger test to see if you hear thud (throw) or ping (glaze).  

However I don’t know what happens to repeated bisque.   I’d love to know how your glaze fire worked. 

I would not trust your test tiles though.  

If your pots look like they are not taking glaze warm them in your oven or kiln at lowest temp and then glaze.  

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Thanks for the advice. All pieces appear fine.  Will try them this week and update here. Many thanks guys. I was very daunted by the controller on this kiln. No doubt programming the glaze firing will be a challenge too. I am only going to fire to cone 5 or6 as I’m using mainly amaco pc glazes. It’s the controlled cooling that this kiln offers that I’m not used to. I may leave that function off for now.

i should have L plates on my bac ; )

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