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Home-made fire clay?


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#1 rdennett

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Posted 13 July 2009 - 12:08 PM

Is it possible to make home-made fire clay? That is, mix it with stuff you dig out of the ground? If so, what type of earth should I be looking for? I live in Austin, Texas.

Thanks,
Rob

#2 HWooldridge

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Posted 13 July 2009 - 01:35 PM

Yes, since all clays originally come out of the ground - but it's easier to go to a material yard (Keller's in San Antonio) or a pottery supplier (Clayworld, also in San Antonio) and buy what you need. That way, you get a clean supply with known properties.

#3 welder19

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Posted 13 July 2009 - 01:44 PM

Your basic fireclays are really cheap any how, not worth trying to dig your own, the last bag of EPK I bought, which is a kaolin clay with a much higher temp resistance than most basic fireclay's, cost me I think around $10-$11 for a 50lb bag.

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#4 meinhoutexas

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Posted 13 July 2009 - 11:42 PM

havent tried this but have heard talk of kitty liter just damp enuf to tamp into place. Again just my 2 cents
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#5 rdennett

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Posted 14 July 2009 - 09:25 AM

havent tried this but have heard talk of kitty liter just damp enuf to tamp into place. Again just my 2 cents


Kitty litter is made of bentonite, IIRC. I don't think that is the same as fire clay. I was just wondering if I could make home-made fire bricks or gas forge lining will stuff in my back yard.

Edited by rdennett, 14 July 2009 - 09:38 AM.


#6 ThomasPowers

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Posted 14 July 2009 - 10:19 AM

Depends on what's in your local ground. Where I live there is a bentonite pit and a pearlite mine and so the answer is *yes*. Back in OH the answer was no.
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#7 welder19

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Posted 14 July 2009 - 10:21 AM

You can, it just may not hold up too long, depending on what type of clay you have in your area, but all clays come out of the ground so you might get lucky and find a high refrectory clay in your yard but you will have to test/experiment with it to find out.
Some but not all kitty litter is bentonite clay and it is good for use in molding sand for metal casting but will not hold up to forging temps not for too long any way, and when using it, it should be ground up to a fine powder.

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#8 Charlotte

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Posted 14 July 2009 - 11:56 AM

If you look around your area you may find a creek or a hwy road cut that has a clay out crop. The clay for claying a coal forge does not need to be top quality. Most clay that has a "greasy" feel will be good enough. The main thing is to get the trash out and and a little white sand if it doesn't have any.

#9 MattBower

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Posted 14 July 2009 - 12:27 PM

I believe there are kaolins and ball clays "growing wild" in Texas, but you're still likely to waste a lot of time hunting down and mining a pure source. Impurities (esp. iron) destroy the refractoriness of the clay. And as someone else pointed out, clay is cheap. Dirt cheap, in fact! It's hardly worth the effort to dig your own, unless you happen to be sitting right on top of a vein of pure kaolin.

You're in Austin. It's an artsy-fartsy kind of place. There must be a pottery supplier there. I suggest you go buy some EPK or a good ball clay, and be done with it. But realize going in that working with raw clay is a much, much bigger pain in the rear than working with commercial castable refractories, etc.

Here, I went ahead and found a place in Austin for you: ARMADILLO CLAY - Equipment, Tools & Glass

Their C&C ball clay is $11.65 for 50 pounds. It's a cone 33 clay; EPK is cone 35, so C&C is very nearly as refractory as EPK. (Both should handle 3000 degrees F without much trouble.) Or you can buy EPK for about $18/50 lbs.

Note that homemade firebricks will require a lot of fuel to fire properly; it's unlikely you'll be able to do that economically, compared to buying them

#10 Jim L.

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Posted 31 October 2009 - 09:35 PM

The refractory that I came up with works OK, but I think I mixed it too wet from what I've been reading. I just used some whit brick mortar mixed with pearlite.

Jim L.

#11 MattBower

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Posted 31 October 2009 - 09:45 PM

I believe normal masonry mortars are based on Portland cement. Portland will not stand up to anything even close to forging temperatures. It sets by becoming chemically hydrated, when you heat it up you reverse that process. It can also spall violently as that water turns to steam, though this might not be as big a problem with a porous aggregate.

This is why commercial castable refractories use things like calcium aluminate cements.

#12 Pac

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Posted 17 November 2009 - 02:43 PM

If I have ten pounds of fireclay, do I use the same amount of sand? I also have about five pounds of crushed clay pots to add, do I need more??

Thanks,
Dave

#13 ThomasPowers

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Posted 17 November 2009 - 04:25 PM

Having melted terracotta pots in my coal forge before, are you sure you want to use them as grog?
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#14 Pac

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Posted 17 November 2009 - 06:20 PM

Would something else be better or can I just use the fire clay and sand?

#15 Nakedanvil - Grant Sarver

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Posted 17 November 2009 - 06:55 PM

No experience with home-made, but I've heard that you should put sawdust in. makes it porous and allows steam to escape once the sawdust burns out.
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#16 pkrankow

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Posted 17 November 2009 - 08:40 PM

I've read the sawdust deal too. I have also read that it takes several low temperature firings (kindling fires) to charcoal the sawdust before you can try a full temperature firing to burn the charcoal out.

Porcelain, which is kaolin, starts vitrification (recrystallization) at high red heat, some 1500F. It will eventually fully vitrify at forge temperatures. It starts to melt north of 3000F.

Sand will melt at somewhere around 1000F. Sand is used as flux in our craft. Keep it out of refractory mixes.

I never tried making anything other than a reflective coating, and I used a very high percentage of Zircon which is a grog till 2800F when it starts interesting chemistry. ZiSiO4 (Zircopax or Superpax) slowly turns to ZiO2 (cubic zirconia) at that temperature and becomes a much better IR reflector than ZiSiO4. This may be why ITC products cost so darn much.

Calcined kaolin is not grog as it is never heated to vitrification temperature, it just has bound water driven off so it shrinks less. On the topic of shrinkage plan for it and create joints that can be filled easily after it has shrunk if you are casting in place.

Anything else you're going to have to look up yourself. I kept to a glaze. Start reading up on ceramics and high fire clay bodies. (cone 10 or higher)

Hope this helps
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