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Help. Where To Start? Clay-Firing

clay wheel firing propane

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#21 Colby Charpentier

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Posted 28 February 2014 - 02:46 PM

A lot of the suggestions here about taking classes or learning before jumping into this SHOULD be heeded. I have built kilns to be used with limited resources in situations like you mention, where not much is available, however, there is no short-cut to learning kiln building, firing, and clay work all at once.

 

The closest thing that I've done to a high-fire home-made gas kiln is the Shopping-Cart-a-gama. This was a collaborative kiln project built using a shopping cart as a frame. I needed a portable kiln that could be fired off with a weed burner and a 20 lb propane tank. The kiln is insulated with soft brick, fiber frax, and steel flashing on the outside to protect from the weather. The stack is 9" steel duct, and a frax-lined mailbox was added to the throat of the kiln once I realized the propane wasn't full combusting before reaching the pots (this helps heat more efficiently). I fire this kiln to c10-12 and add soda ash through the throat of the kiln and through a spy-hole. I have once-fired in this kiln, about half the time, and it does fine as long as the early portion of the firing is gentle. I can get a firing down to ~2 hours from green to c10, however, the firebox is fairly small. The shopping cart interior dimensions minus the fiberfrax and softbrick leaves enough room for about 12 beer steins. I'll generally use about half a propane tank per firing. I also found that I need forced air to compensate for the shorter stack I was using (like an artificial draft), a box fan worked fine for this.

 

In regards to Sheffield Clay, I love them. I live about 3 hours away, and drive out, getting ~500 lbs at a time (or whatever my vehicle can handle). I highly recommend their schoolhouse white. It's smooth, white, and forgiving. It doesn't perform as well on larger forms, but for functional wares, it's absolute tops, especially for the price. S-14 is a great groggy stoneware, great for hand building or throwing and it stretches great, without complaint. I have had less than a positive experience with their W1A, but that's in pushing a bit above the c6 rating of the clay.

 

Good luck in any case...



#22 Benzine

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Posted 28 February 2014 - 06:16 PM

Colby, that sounds like quite the kiln. Do you have any pictures of it? Seriously though, did you say two hours to cone 10?!
"Anything worth believing, is worth questioning"

#23 High Bridge Pottery

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Posted 28 February 2014 - 07:32 PM

I agree, would love to see what it looks like. Takes me 7 hours to get to cone 10 in my small 3kw kiln and that is from bisque.

 

I wouldn't rush into buying a kiln as you are not going to replace it any time soon. It could easily still be going 20 years down the line.

 

I picked up my 3kw kiln from people who do house clearances. I don't think the elements had ever been used! It is just in a sorry state on the outside as whoever owned it kept it outside.



#24 CecRR

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Posted 28 February 2014 - 10:24 PM

Thank you Colby! This is the kind of input Ive been hoping for. I know its going to be hit and miss for awhile, thank you for recommending a base clay to try out. I worry about the raku, and high grog content of some clays. I have a certain type of eczema that occurs on my hands, and have worried about what will 'chew my hands up" thank you to Benzine, and Pres for pointing out how harsh grog clays can be. I LOVED porcelain when I worked with it before, but am obviously looking for something more cost efficient while getting back in the swing of things. Im fine with learning with a raku kiln. It would be fun to work on throwing some basic pots for outdoor plants, decor etc. Maybe one day I can get to the point where I will be more knowledgeable when it comes to kilns and be able to stumble across something affordable. We do have a very small school here which has a kiln, they fire once a year tho, so Im not sure on the availability to use it. Thanks for all the help! :) 



#25 Benzine

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Posted 28 February 2014 - 10:51 PM

Im fine with learning with a raku kiln. It would be fun to work on throwing some basic pots for outdoor plants, decor etc. Maybe one day I can get to the point where I will be more knowledgeable when it comes to kilns and be able to stumble across something affordable. We do have a very small school here which has a kiln, they fire once a year tho, so Im not sure on the availability to use it. Thanks for all the help! :)


Raku kilns are great to work with, but I still think you will have issues, if you try to bisque/ single fire in them. Now if you are doing something more like Colby did, that would make more sense.

In regards to the school's kiln, maybe if you did a little barter with them, they'd let you fire more often. Give them some clay or glaze, in exchange for the use of the kiln. If it's an electric kiln, they don't cost much to fire it all, so they'd probably come out ahead on the deal.
"Anything worth believing, is worth questioning"





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