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Thread: DIY Refractory Compositions

  1. #91
    33.3% by weight bentonite clay from ground cat litter, sifted through window screen
    66.6% quikcrete washed fine white silica sand

    I rammed it up like a sand castle and let it dry. It has basically no insulating properties but I've had it over yellow heat multiple times and it hasn't even sintered together yet! Unfortunately this means that I keep damaging it because it's essentially a dry sand castle - little green strength.

    Pros: Might take 3000F to melt it, cheap, homemade.

    Cons: You have to actually get to 3000F to sinter it or it has no strength, poor insulator
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  2. #92
    i read the whole thread and didn't see any answer to this question by ToastedWilliam, so i went looking. apparently gypsum plaster, KOH (lye), and bentonite are part of a capping mix for radioactive waste piles...

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  3. #93
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    welcome to the forum Tinker Jason

  4. #94
    Does anybody know if any of these could handle 3000F + temperatures? or if they all could? I dont really want to be replacing the refractory every other week
    Well OBVIOUSLY, you don't know how we do things around here!

  5. #95
    Administrator Site Admin Anon's Avatar
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    Certainly not all of them. The recipe in my book can. Otherwise, any recipe with lots of alumina and very little flux (no Portland cement, no plaster, minimal bentonite, not enormous amounts of dirty silica sand) will do as well.
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  6. #96
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    Hi to all, first post. I just completed my first oven and made my own refractory. After reading all the post on the mixes, I expermited with the fomula and came up with this:
    2 parts sand
    1.5 parts vermiculite(because I had it)
    2 parts type f fly ash
    2 parts chalk clay

    The chalk clay is a local white clay that I had used once before in a wood fired outdoor oven and seemed to work ok in it. It is used here in the south to seal water ponds and must be kept under water or it will dry hard as a brick. The fly ash is from Boral and I use it in making compressed earth blocks instead of portland. Boral makes a fired tile out of it and so I thought it might be a good thing to try. I can't afford the $100+ a bag for refractory so this is think will work better then portland. It will be a few days before I fire the oven so will let you know what happens.

    I want to thank every one who contributes to this site as it is very helpfull for people like me who know absolutely nothing about foundry work. My main purpose in doing this is to smelter gold ore (when I find some!) Has anyone out there done any gold smelting? I have the chemical formulas for the flux, just haven't done any black sands or ore yet. We'll see....

  7. #97

    New and wanting to Build first refactory

    Hi I'm new to this and wanting to make a start on building. Been reading through your thread and been out buying stuff, seemed like a good idea at the time. here is what I have got

    16 litres of tesco Kitty Litter (I believe this to be Bentonite)
    25 KG Sand not sharp but clean from my builders yard
    8 Litres of Perlite from B&Q
    5KG Portland Cement (why don't know but seemed like a good idea at the time)
    25kg Mastercrete (just plain concrete powder)

    Large Metal bucket (Green from Ikea looks pretty)
    small plastic bucket for insert
    old chinup bar for blasting in air

    And I'm looking to make a charcoal fired Refactory.


    My question to you guys is. using this load of stuff what is the best mix for melting. I'd like the option to melt more than just aluminium, and have it last a while. As I said I am new to this and have read loads on this but seem to find loads of conflicting information. I live in Edinburgh Scotland were clay is real hard to come by. I have asked the local potter adn they have no idea. Can't get fire clay. Any help appreciated...

    Billy

  8. #98
    Senior Member 4cylndrfury's Avatar
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    Welcome. Your post is probably not best suited to this thread, but we dont mind helping.

    Any plain concrete will fail after heat cycling up to aluminum temps, and is definitely going to fail if you go much higher. You need some clays that calcine at high temps like Kaolin clay or Fireclays. You can buy them online if they arent available locally. Firing any clay based refractory is likely to be a problem if youre using charcoal. Its not a very even heat, so the firing will be uneven and prone to failure.

    For real refractory, try boiler intallation companies, and for kaolin, try that potter again. Then read Anons tutorial, theres a LOAD of good stuff in there regarding refractory makeup and use.

    p.s. if youre going to fire your furnace with coal...just bury that steel bucket in the ground and plumb your air to enter from the center of the bottom of the bucket. Charcoal is fairly self insulating, no need to go to great lengths to insulate the furnace as well.

    Good luck

  9. #99
    Quote Originally Posted by wbrcasson View Post
    Hi I'm new to this and wanting to make a start on building. Been reading through your thread and been out buying stuff, seemed like a good idea at the time. here is what I have got

    16 litres of tesco Kitty Litter (I believe this to be Bentonite)
    25 KG Sand not sharp but clean from my builders yard
    8 Litres of Perlite from B&Q
    5KG Portland Cement (why don't know but seemed like a good idea at the time)
    25kg Mastercrete (just plain concrete powder)

    Large Metal bucket (Green from Ikea looks pretty)
    small plastic bucket for insert
    old chinup bar for blasting in air
    you would be much better off if you had some fireclay in that mix. 25% would be a good place to start. and the portland will not help you
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  10. #100
    Thanks for the advice guys. Clay seems to be the answer. I had hoped the Kitty litter would suffice but from this thread I see that not to be the case. Unfortunatly I can't bury it in the garden. Also I have trawled all over Edinburgh today painfully trying to find any fireclay or good substitute. No sales assistent knows of any. I was hoping to get this started tomorrow but alas I shall have to order online and await delivery. I have a mill and lathe arriving in a week so hope all is done by then.

    Billy

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