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low fire - firing cycle...


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#1 nartist

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Posted 06 March 2012 - 10:11 AM

I've been bisque firing cone05 for about 1 yr, in a Duncan/Teacher's Plus kiln.
It's a modest size (smaller than avg) - 240volts: It is smaller than normal...
17.5 " x 20" (depth)
The bisque seems to be firing fine, no problems but.....

I'm trying to figure out the firing cycle - on cone 05/automatic mode (their setting):
it only seems to take approx 5-7 hours to shut off.

--- THIS SEEMS like a very short time and i'm wondering why...
Is the bisque really getting fired in a strong way???
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My guess is it is due to the kiln size being smaller than avg.....?
Most other kilns i've fired have been larger and take around 10 hrs for a bisque...
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The manual (and the Duncan/Paragon cust support) dont have much info...
The manual says (in auto mode) - kiln is on low for 2 hours and then will
"switch itself to the ceramic mode (bisque-c0ne 05) for remainder of cycle"
So, that being said - if it takes 6 hours to fire --> 2 hrs on low then it takes
4 hours to bring up to cone 05...
Doesnt that seem short??????
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Also, In the manual, it says...
firing cycles depend (in general) on:
thickness of ware :firing kids projects, mostly slab - 1/4 "
kiln size: 17.5 x 20 "
amt of ware - almost always a "full load"
and voltage variations - have been checking on this... not sure how much i have to do this in-depth:
as of now: just checked volts w/voltmeter on outlet plug

#2 scoobydoozie

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Posted 06 March 2012 - 11:09 AM

From your post and questions, it sounds like you are not using witness cones on the shelves. Duncan is a reliable company and unless there is something wrong with the kiln, I would trust it knows what it is doing. You can confirm that the firing is adequate and complete by using witness cones on the shelf and examining them afterward. That's the best way to determine if the firing is correct for any electric kiln. To be most accurate, use a witness cone equal to the cone you are firing to and also one hotter and cooler. That way if the firing is not correct, you will have an idea what cone it IS firing too on that setting.

You should always use witness cones ( but I don't and use them only occassionally as a check up. Shame on me.... Posted Image )



#3 Chris Campbell

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Posted 06 March 2012 - 11:10 AM

That sounds right to me ... 5 to 7 hours for bisque. 05 is not really that high a temp for your kiln to reach. If your witness cones are properly bent, if you are pleased with the results and your glazes come out OK ... then all is well.

People who use red clays with a lot of impurities in it prefer to fire very slowly to get all that stuff burnt out but there is debate over the validity of that idea too.

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#4 TJR

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Posted 06 March 2012 - 12:38 PM

Nartist;
This sounds like the correct length of time to me. Having witness cones is a good idea to check the temp. Also, you could consider lowering your bisque temp to cone 07 or cone 06. This saves energy and time.
TJR.

#5 neilestrick

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Posted 06 March 2012 - 03:05 PM

Small kilns often fire faster than large kilns, especially when using mechanical switches. As long as there are no problems with your glazes, everthing is fine. If you notice any bubbling or pinholing in your glazes then you may not be bisque firing effectively. Your best option in that case is to bisque hotter, as high as cone 03, to make sure everything gets burned out.
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#6 nartist

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Posted 13 March 2012 - 12:44 PM

thanx for the replies!

I've been using this kiln over the past 2 years - firing about 2 times/week
almost every week.... been working great....
Yes, i have checked the firing with witness cones - extensively....
They are bending properly - glazes look good... I'm not trying to troubleshoot any particular problem with the firing of the kiln.....

I was just hoping to understand the firing cycle and learn more about it....
i'd like to start expiramenting with changing the cycle.

I looked at manual, called duncan and cant find a good resource that goes beyond the....
- first 2 hours of the cycle....

thx.....

#7 cam

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Posted 20 October 2012 - 11:41 AM

Small kilns often fire faster than large kilns, especially when using mechanical switches. As long as there are no problems with your glazes, everthing is fine. If you notice any bubbling or pinholing in your glazes then you may not be bisque firing effectively. Your best option in that case is to bisque hotter, as high as cone 03, to make sure everything gets burned out.


I am on this site looking for solutions to my pin-holing problems. I have an old small manual Skutt and a newer Cress. In both I try to bisque fire to ^04 for glazes designed for ^5-6. I'm mostly using Standard Clay 182 (a white stoneware) and 112 (a brown with manganese). Am I to understand that bisque firing to ^03 may help? It won't make the pot too tight? to absorb the glaze? Any other suggestions would be appreciated as well ...

over my head

#8 neilestrick

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Posted 20 October 2012 - 11:57 AM


Small kilns often fire faster than large kilns, especially when using mechanical switches. As long as there are no problems with your glazes, everthing is fine. If you notice any bubbling or pinholing in your glazes then you may not be bisque firing effectively. Your best option in that case is to bisque hotter, as high as cone 03, to make sure everything gets burned out.


I am on this site looking for solutions to my pin-holing problems. I have an old small manual Skutt and a newer Cress. In both I try to bisque fire to ^04 for glazes designed for ^5-6. I'm mostly using Standard Clay 182 (a white stoneware) and 112 (a brown with manganese). Am I to understand that bisque firing to ^03 may help? It won't make the pot too tight? to absorb the glaze? Any other suggestions would be appreciated as well ...

over my head

First, 182 is not ideal for cone 6. It is really a cone 10 clay. If you want a smooth cone 6 clay try 240. It's not quite as forgiving as 182, but it's a really nice body to work with. If you are getting pinholing with an 04 bisque, going up to 03 probably won't help. If you're firing to cone 5, try cone 6. If you're already firing to cone 6, try adding a hold time onto the end of the firing. Start with 5 minutes. If that doesn't do it try 10 minutes. Adding 15 will get you close to another cone higher, so at that point you may need to reformulate the glaze.
Neil Estrick
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L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

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