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porcelain firing schedule needed


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#1 GaryFBrown

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Posted 16 April 2013 - 12:47 PM

My electric kiln is not properly programed for the pieces I am firing. I hand sculpt in porcelain, using the coil technique, pieces with very thin walls (1/8 -1/4 inch). I need to program an appropriate firing/ramp/time/temp schedule that will fire my work without slumping it. I spend around 40 hours per piece and have experienced a couple of heartaches. I've not been into the studio for a while and would love to get back out there, but can't justify spending the time until I resolve my kiln problem. I need 2 schedules, one for cone 10 and one for cone 6. Any help would be appreciated.

Thanks.

Below is an example of the work I will be firing.

Attached File  oceanicawix.jpg   333.63KB   37 downloads

#2 neilestrick

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Posted 16 April 2013 - 09:27 PM

The problem is not the firing schedule. If your clay is slumping, you need to fire cooler. It's called pyroplasticity- the clay becomes plastic, or soft, as it heats up. The closer it gets to its melting point, the softer it gets, and slumps. Try firing a cone cooler and see what happens. You may have to adjust your glazes slightly.
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#3 GaryFBrown

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Posted 16 April 2013 - 10:45 PM

I can certainly understand that. However, I do believe that my kiln is completing it's schedule to rapidly. After speaking to my college instructor about it, he was very surprised at how quickly the heat ramped and the short time that it took to complete the firing. What I wasn't able to get from him was a clear answer to the soak times and how quickly the temp should ramp during the stages. I would also like the cool down to be controlled and not just the natural electric kiln cooling time.

#4 Marcia Selsor

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Posted 17 April 2013 - 07:27 AM

You may also need to add some molochite (used as a porcelain grog) to give the clay body more strength.
Sculpting with porcelain isn't easy.
Very nice example of your work.

Marcia

#5 Chris Campbell

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Posted 17 April 2013 - 10:00 AM

I work in thin porcelain so I would offer this ...
Porcelain slumps and needs to be supported in order to have successful firings. I make forms from higher firing clays to support all of my work ... Once a porcelain form veers from being self supporting (cylinders) it wants to slump. Firing down will definitely reduce cracks but will not help with slumping.

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#6 GaryFBrown

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Posted 17 April 2013 - 10:34 AM


You may also need to add some molochite (used as a porcelain grog) to give the clay body more strength.
Sculpting with porcelain isn't easy.
Very nice example of your work.

Marcia


Thank you. I'm going to research molochite. That will, likely, be VERY helpful to me. What ratio would you suggest?




#7 GaryFBrown

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Posted 17 April 2013 - 10:39 AM

I work in thin porcelain so I would offer this ...
Porcelain slumps and needs to be supported in order to have successful firings. I make forms from higher firing clays to support all of my work ... Once a porcelain form veers from being self supporting (cylinders) it wants to slump. Firing down will definitely reduce cracks but will not help with slumping.


Some very good advise. It would make glazing difficult if not impossible, though, would it not?

#8 Chris Campbell

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Posted 17 April 2013 - 12:48 PM

One solution is to reverse your firing process ... First firing is high, glaze firing is low. Your porcelain will not slump at low temps.
Another is to only glaze inside surfaces.
Another is to combine the two methods to suit your work.

Chris Campbell
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#9 GaryFBrown

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Posted 17 April 2013 - 01:07 PM

One solution is to reverse your firing process ... First firing is high, glaze firing is low. Your porcelain will not slump at low temps.
Another is to only glaze inside surfaces.
Another is to combine the two methods to suit your work.


That is a fantastic suggestion. Thanks




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