Ultimate Guide to Making a Cheap but Effective Aluminium Forge.

There are many guides and many ideas I've collected and, being that I completed this (the first one... I made a completely new setup just for this instructible... you should feel special.) within two days and most importantly... cheaply.

My cousin /assistant / camera man and I created this instructable so we could share our wonderful smelting smelting experience and win the hearts and minds of the instructable community.


This instructible includes fire and molten metal.

Also; If you mortally wound yourself while duplicating this instructible, please delete this from your history internet history before dieing. i don't want to be held liable.


We shall begin.
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Step 1: Parts / Tools

In retrospect, the parts / tools list quite long but it should be things that are easily available.

The most expensive thing was the torch. I'm really cheap but it turned out to be a rewarding investment.

The other parts are as follows:

Quick Setting Quickrete (I got a 20 lb bucket for under 10 bucks)
Something to mix the Quickrete in
Something to stir the Quickrete with
Large Coffee Can (6 inch)
Small Coffee Can (4 inch)
Hack Saw (or any metal cutting tool)
Drill (or metal punch or improvised hole making tool)
An empty 14.1 oz propane tank (make sure it's competently empty)
Scrap steel bar like from a printer, about a foot long (you can buy 5/8 steel bar at lowes)
A sharpie (or any marking tool)
Short (about 2 or 3 inches) iron or steel tube that the torch head fits in. (optional)
A ball peen hammer (any hammer will suffice)
Some propane gas (i buy the ones for camping stoves because their $4.38 for a 2 pack of 16.4 oz tanks.)
An oven (optional)
A vice. ( kinda optional. you could find another way but i find the vice necessary)
A mini muffin tin (optional. you just need something to pour the aluminum into.)
Some cheap thin steel wire (1/8 diameter max. but strong enough to hold some weight)
justin556 years ago
im not sure exactly what the cause was but last weekend i had a propane torch and i decided to heat a penny with it and discovered that it melts, then i did it on my wet carport and it exploded all over my face and it looks like i scraped up my face really bad, i could have been blinded easily and i recommend being very careful with water!!!!!!!!!

Glad you're okay. Basically, as soon as the molten metal got in contact with the water/moisture it turned it to steam almost instantly, that expansion (volumetric ratio well above 1:100) is what sent the molten metal flying upwards. Again glad your okay, especially your eyes. There is a very good reason foundry workers get around in all that protective gear...

It's the same reason that you don't place water onto a grease fire. The water rapidly (very, very rapidly) turns into a vapor. When it turns to a vapor it expands and moves outwards. In the case of a very hot liquid, the water turns into water gas and pushes everything outwards. There is no need for a chemical reaction. Rather, the physical transition between phases is what causes the explosion.
actually if the grease or oil is hot enough the water decomposes into hydrogen an oxygen instantly ignites and creates a huge fireball might look cool but is very dangerous
Water decomposes into hydrogen and oxygen around 3,000C. Then plasma incineration. Cooking oil (such as canola) top out around 500F. So it is simply a phase transition. As a solid or liquid transitions to a gas they expand and occupy much more room. When this transition and expansion happens very quickly it is termed as an explosions. A bomb undergoes a chemical reaction that gives off heat and gas at the same time which makes it occupy more room very quickly. Gundpowder is a great example. Just a tiny bit can hurl a tank shell for miles. Water thrown into a 500F fire immediately and rapidly expands into a gas. This transition throws oodles of burning oil into the air. Not a lot of fun to be around. But no chemical reaction is necessary.
some pennies melt because at some point they started making them out of zinc (someone correct me if I'm wrong) that explosion was probably the concrete exploding underneath the molten metal when it was heated, because there is still small amounts of water in the cured concrete...when you heat it, that water turns to steam, creating lots of pressure, eventually it explodes due to built up pressure , thats why you use so little water in the cement when you make this furnace, you also have to ram it in to eliminate any air pockets.
In 1982 they switched from basically pure copper pennies to copper coated zinc. In fact, pre-1982 pennies are worth more as scrap copper than they are as pennies.
1944-1982, US pennies were 95% copper. 82 and newer are a zinc blank, with a copper wash.

Wikipedia on Pennies

WesDoesStuff (author)  Jonny Appleseed6 years ago
well put
WesDoesStuff (author)  justin556 years ago
ya probably shouldn't have done that. ; ) chicks dig guys with scars. be safe, be well, and thanks
hahah true that, Hockey player here. split my chin open 4 times now. 9 stiches each time. funny thing is, i didnt realize i cut it till the EMT came up to me and was like, your going to need stiches. i looked in his mirror and i had blood all the way down my neck. happens evrey time.. i still get some hot *** biznatchesss
jsyson15 hours ago

I work in a iron foundry, and I can't stress this enough: KEEP WATER AWAY FROM MOLTEN METAL.

Furnaces can, and do explode due to molten metal + water. Not just a pop, they can literally explode and rain down molten metal. people have been killed by 2 ton furnaces exploding, google it! Molten metal turns water to steam so fast, it expands in a flash, and can send molten metal flying.

I see these warnings below from people in the industry being dismissed by people without experience - I don't understand this, WHY do you think he is commenting?

Not to mention that aluminium is more dangerous, even though it has a lower melting temperature, it reacts (chemically) a lot more dangerously than say iron or steel.

jsyson1 jsyson15 hours ago

Might I suggest a bucket of sand as a safety measure instead of water. Much better idea...

As far as improving this little furnace goes: Why no lid? Heat rises, and that's where your going to loose most of your heat. Get another tin the same as the bottom, cut it to 1.5" tall, add a 1" vent hole at the top, and two slots for the crucible handle to come out of, then form the refractory (concrete lining) as you did on the bottom.

Also important: LET RECRACTORY COMPLETELY DRY BEFORE USE. Fire the furnace up on low heat and increase over a few hours to set and harden.

Vise, not vice. Vise is for holding things, vice is for having forbidden fun.

LMAO forbidden fun.

Hey, I cut into the propane bottle using a simple metal cutting blade on a hacksaw. Just make sure that when you are cutting into it the tank is empty and has NO pressure. Pressurized propane even when not exposed to sparks or flame is still dangerous as it is a pressurized gas and is pretty cold. You definitely don't want to use a torch to cut a bottle in half. I haven't built the kiln yet as I don't have a torch that will cut steel. I will have to use cold cuts unfortunately.

dschwab16 months ago
My father has run a propane business for years, If you are going to cut into a propane tank and do not have any experience i would recommend not doing it.

IF you are going to I am not liable for this advice :P

Drain the tank completely.

Use the stock equipment to leave the gas on once its out and tip the tank upside down, since Propane is heavier then air. We leave ours for 3-5 days like this. Some smaller tanks like torches or camping grill tanks have a port on the side that I have had in the past, used a tool for removing the core from a tire valve air input, to remove from the tank and also help drain.

After that we then fill the tank with water to disperse ANY leftover gas included air which again can be combustable in certain environments.

after these steps almost but not all risk has been reduced but you still should consult a proper propane specialist.

How is it you fill the tank with water before cutting into it?

suboxygen4 months ago
flyman4169 months ago
Hi I really the idea of this cuz I've been thinking of what I could use as a crucible in my forge and I saw this. I was wondering how do you make sure the butane tank (the one that will be the crucible) is completely empty? I showed my dad this and he was like "NO!", but I wasn't about to cut into a pressurized tank like that. We have an "empty" tank but I'm not sure how pressurized it still is. So how do you depressurize it?
pheenix421 year ago
I'm curious, how durable is the Quikcrete as a furnace refractory?
You need to mix the quikrete with fire clay (8 bucks a bag at home depot, silica sand has a lower tolerance but can be used also) which will up the tolerance of the furnace max temperature. also I would advise vibrating the mixture for a few minutes before you have it set. (air bubbles can be potentially explosive, which is why you wouldnt use traditional concrete)
Sounds good, but what ratio of fireclay to Quikrete?
ClayOgre1 year ago
Maybe somebody's already mentioned this, but I kind of wonder about your advice to "have water handy". With the temperatures involved, water tends to turn instantly and rather violently to steam, which can be quite dangerous. If things get out of hand, I would think dumping a bucket of sand (dry) on things might be safer. I've built and operated Dave Gingery's charcoal furnace. The only time I ran into trouble was when I melted a chunk of what I thought was pot metal from an old washing machine. It had some magnesium in it and things got rather exciting there for a bit. Water was not effective, neither was throwing dirt on things. It just had to burn itself out. There were clouds of "zinc smoke". Not good. Fortunately I was outdoors.
for insulation you could use sand or dirt.
foxworrior1 year ago
hello, i really like the instructable and i will try it but i want to know, will a kitchen blowtorch work to heat up he aluminium?

shakeval1 year ago
if you want a more even distrobution of heat, try making a cone, bout an inch or two high and wide enough you can slip it in and try it, your crucible will rest on the point and the heat will be able to whip around the bottom edge with a lot more exposed metal
Kaiven2 years ago
My ingots were cast in a muffin tin but didn't come all. I had to destroy the tin to rip them out because they were essentially soldered to it. Any idea how I can prevent this?
Try coating the tin with soot, like from one of these
I had the same problem, but with this it popped right out, easy as pie.
Thanks! You're the first person to give me a reply!
no problem :) just dont try it with copper, I think its too hot so it burns away the soot and sticks anyways, very annoying
cacci5 years ago
Could you melt salt (NaCl) like this?
yes, you can; however, depending on your objective, you may achieve poor results. Melting salt in a steel crucible will contaminate the salt to some degree (and it tends to eat up the crucible). Also, like the prior response suggested, avoid melting wet salt. The issue isn't so much that the salt will explode. It might bubble a bit as it melts, but the majority of the water will be lost before the salt is even able to melt. The problem is if you're trying to melt a mixture of salts in correct proportions by mass (e.g. to make fluxes). Seemingly dry salt stored in permeable containers will contain a remarkably large amount of water. This will offset any attempts to weigh out the salt charges. The only way to fix this is to dry the salt by heating it. Last method i used was to alternately roast and grind the salt, though a prolonged roasting would work too.

I know these are old comments, but i reply for the sake of anyone who ever hits this via google (like i did)
sure. you could melt salt in this thing, but make sure that there's no i repeat NO water in the salt. if there is, it might explode. maybe use something else other than the steel crucible or use one only for salt, because it might do something weird if you try to melt something else like aluminum in it, because aluminum's melting point is higher than salt's boiling point. also, don't heat it red hot. use an IR thermometer and get it to 900 deg Fahrenheit, but not lower than 800 and not higher than 1000.
curvy772 years ago
when i melted my aluminum cans (all i had and quite a bit =) ) there was lots of slag at the bottom and it fused with my crucible. pushed it down with stick adn squeezed out enough aluminum for 1' by 4' of aluminum ingot. slag at bottom normal?
mmrakozy2 years ago
This crucible doesn't seen far fetched, but what about the holes in the bottom?
Truthfully, i dont like this ible. sorry. i thought it was REALLY cool, but it turned out to be not. i made this thing EXACTLY like this ible said, but in the end, it failed epically. i even had the same crucible as him.  nothing melts! I tryed aluminum cans to a small aluminum pipe. all that happens is the aluminum cans and pipe turn a goldish brown and never melt. is there any possible way to fix this? i have a top and everything. i dont see how this works. HELP!
How hot is your torch burning and what material (steel) is your crucible? Heat passes differently through different metals. Also a good way to tell if your torch is hot enough is simply if you see lots of flames theres not enough oxygen and not enough oxygen means it isnt burning as hot as it could be.
i dont know about using gas to melt it but wood and charcoal work great for melting it. mostly wood. i used the last of my embers from a steel knife craft and i melted 3 aluminum cans in a soup can before the flame went out. (i had a blow dryer to help fan the flames)
what gas you using?

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