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underfired bisque ware


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#1 LisaGrigs

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Posted 04 February 2013 - 04:22 PM

I recently got a used kiln and got it up and running this week. I did a test fire and it was able to reach cone 05 within an hour and fifty minutes. Yesterday, I decided to do a bisque fire. I started it at 7:30 and it seemed like the firing was going pretty good until the last part. I noticed that when I glanced in the peep hole that the top elements were not glowing at all. I know I need to replace them. I had the kiln going for at least 12 hours and it still hadn't reached cone 04 so then i decided to just turn it of and let it be. Today, when I looked at the cone there wasn't even a slight bend in it. What do I do about my bisque ware? When I change the elements should I re-fire them? Or since it was in the kiln for so long and the top elements gave up at the last bit that the bisque ware is okay and I don't have to re-fire? If someone could help me out an answer my question that would be great. Thank you.

-Lisa

#2 mregecko

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Posted 04 February 2013 - 07:43 PM

Honestly, there is no harm in re-firing it. I've refired bisque-ware many times (if you get wax on it, etc). I'd rather do that than have excessive carbons / organic materials that didn't burn out during bisque outgass during the glaze firing.

#3 Chris Campbell

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Posted 04 February 2013 - 08:26 PM

While you are ordering your new elements, order some self supporting witness cones too.
If you fire Cone 04 bisque, get 03, 04 and 05, ... if you glaze fire to 6, get 5, 6 and 7. I put a set of these at the bottom, middle and top shelf of my kiln for each firing.
This bracketing of your final Cone temp will give you a way of knowing what happens on every level of your kiln so you would not have to guess and worry about re-firing.

Chris Campbell
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www.ccpottery.com

TRY ...   FAIL ...  LEARN ...  REPEAT


#4 bciskepottery

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Posted 04 February 2013 - 08:52 PM

You don't need to refire; although the bisque will be more porous than if you had reached ^05. Before glazing I'd wipe them down with a wet sponge so the bisque does not absorb too much glaze -- wipe one item and then glaze, not wipe all the wares and then glaze. Depending upon the clay body, some potters bisque as low as ^010 and as high as ^02. Bisqueing is just to burn out organic impurities and provides some hardness to the wares for handling during glazing.

#5 LisaGrigs

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Posted 04 February 2013 - 08:58 PM

Thank you for answering my question and giving me some more advice along with it. I appreciate the help.

-Lisa




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