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Hey, i'm planning on making a small foundry for aluminum, I plan on using a mixture of Fire mortarclay, portland cement, and silica sand. Can anyone suggest a ratio and amount of water i should use. 

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you posted in solid fuel FORGES asking about a foundry with explosive material for the lining,  are you sure you are in the correct place?, this is I Forge Iron, we do have a foundry section, that explains a little of this, I suggest you start by reading before you hurt yourself trying to reinvent the wheel

I will relocate this as it makes little sense where you posted it

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Welcome aboard, glad to have you. If you'll put your general location in the header you might find forum members within visiting distance.

We aren't trying to discourage you but you've just run smack dab into the problem with using the internet for "research." Without having enough knowledge to sift the good from the BAD you can't really learn much. In fact the more marketers dictate search results the more worthless adds block good info. It's coming down to the point I turn my computer on to a long string of infomercials.

Try the library, real, bound, paper books are far more informative than the maelstrom of the internet.

NO Portland cement in a refractory. Like said already that's just plain DANGEROUS and a good example of why you should NEVER take what's said online for granted. You MUST verify what you read.

Frosty The Lucky.

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I have used portland cement in the past, using the recipe at the site formerly known as backyardmetalcasting.com.  I forget what they're called now.  If I remember correctly, it was 1 portland cement, 1.5 parts sand, 1 part perlite, and 1.5 parts fireclay, with the first three mixed together, then fireclay added last and mixed with as little water as you can get away with.  It worked...but it was problematic.  

Definitely not as effective as a good refractory.  I used it on and off for several years without spalling at temperatures suitable for melting aluminum or lower temperature metals, but at higher temperatures, it..well, it didn't explode, it just kind of degraded, got brittle, and fell apart a lot quicker.  Pieces started to break off of the inside and required patching when you poured bronze, copper, or brass.  Not explode, just kind of cracked and gradually fell to the bottom over multiple uses.  Not really desirable, and you ended up having to cover your crucible.

I did have one rather glorious explosion in one furnace, but that was due to a failure to ram the refractory in properly,  which allowed a gap in which water collected.  The thing about cement is it's porous.  And any porous material that collects water is prone to nasty steam explosions.  Honestly, with homemade refractories, I did about as well with a 50/50 sand/fireclay mix over grog, with maybe 10 percent straw or sawdust built in and baked out.  It's about as effective as a refractory, and easier to work with.  The real way to go is to buy a proper refractory and use it.  It's cheaper in the long run, and far more effective.  Have you looked at the Gingery books, or the website above?

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