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firing large ( 40"x30" ) sculpture

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I have a finished sculpture that is 40" high and30" wide and about 1.5" thick.

Does anyone have any experience firing something this big?  I am having a hard time finding 

a kiln big enough that can fire it?  I already have made a mold but would like to save the original.

If I can't get it fired , how would you go about finishing it? 

thanks, chris


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clay type is a moist clay .  4-6 cone

there is no back side, meaning it is not 360 dgrees

its approx. 100 lbs and been drying 2 months

this is me pulling mold off,,but you can see it is open at the back



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There are kilns large enough out there to fire this, but I don't think you want to buy one. about 4-6K. My solution to your problem would be to locate a local college/university that has a ceramics program. Most of the larger schools would have gas fired kilns. Contact with the Art or Ceramics department would possibly get you in the door, but you would have to convince the professor in charge of the ceramics program to allow it to be fired in a load. You should have available with you when you meet with anyone: good pictures, clay type with manufacturer, and the drying time of the piece so far. It could probably  be bisqued with a standard load, but I doubt that they would be firing a cone 6 glaze load in the larger kilns, but then I may be wrong as cone 6 is very popular for ceramics right now .




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TY CPD... Congrats on a very niece piece. You have an appreciable talent.

1. Due to the weight (75lbs. +|_) dry, you will have to fire this on a bed of course sand. Some would suggest wadding, but I think this piece is too heavy for that method. Clay will shrink 10-14% when you fire it! which means the base that makes contact with the kiln bottom will shrink that much as well. So you MUST plan for that movement, and allow it to move without drag; otherwise you will crack it.

2. Absolutely fire on slow speed (108 F) an hour climb. This piece is 1.5" thick, so it will take time for heat to penetrate that thickness. I have read studies from various Universities using lab equipment to measure the effect of heat on clay. For instance; if the surface of the clay is 1000F, it could be an additional 30 minutes before the core reaches that temperature. One of the reasons extended holds are often used to cure pinholes and  give clay the time to finish off gassing.

3. Quartz Inversion.  This will be the problem child for this piece due to its weight , size and thickness.quartz Inversion is when the silica in the clay (quartz) converts from the alpha to beta stage at 1065 F or so. I think for those across the pond it would be 563C. The simplified explanation of this reaction would be: a molecular earthquake. All the clay particles start vibrating ( reaction to heat)  to the point it can literally split the piece. Many threads on the topic. Personally, I would program a 50F an hour climb from 1000 to 1150F to make sure  the heat equalizes in the core.  You cannot push this piece too fast through this critical temperature range.

4. This piece will require an extended hold at peak firing temperature in order for the heat to reach the core. At minimum I would suggest 30 minutes. Personally, I would candle it for a few hours just to make sure it was driy to the core before starting the temp climb. Others might find that excessive, but I see it as a few hours of added insurance. Too nice of a piece to take chances.

i have a 15.5CF kiln: the maximum piece would be 24 x 24 x 34 tall. You need to locate a kiln in the 20CF range to fit this piece in.


Edited by glazenerd
Spelling corrections... As usual.

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if you find that there is no kiln available within a reasonable distance, maybe you could try something really different.   there are people all over the world whose work is too big for a kiln so they build a kiln around the piece and fire it with wood or other burnables.  i remember the ceramics monthly article years ago about the horse sculptures in India that were done outside with help from an entire village.  it was a celebration and i think the horses were built for that event.

steve mattison has a section showing an in situ firing in his book, The Complete Potter.  see pages 206-7.  this was an international effort with the artist from denmark, a kiln builder from usa and the huge  sculpture was fired and left in portugal.

a smaller scale firing might be just what you need.

Edited by oldlady

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I have no idea where or how to fire it, but if ultimately you cannot fire it and you've already made a mold then you might be able to make it again out of Portland cement or some other concrete product. It would be extremely heavy it might even need some steel ,  but I guess clay is heavy too... Just a thought . 

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