Introduction: Build a Foundry and Sand-cast Aluminum.

Picture of Build a Foundry and Sand-cast Aluminum.

Hello instructableers, DIYers, and Internet people everywhere! Welcome to my debut instructable!!!!
(Whooo, We love you Fenris! You rock! Give me your socks for my creepily obsessive collection of things related to you!).

Thank you, thank you! But really, I must get to the instructable, settle down please.

In this instructable, I will detail how to construct a simple, cheap, and effective foundry, capable of melting aluminum. This foundry can be built quickly, with little tools or money, and is great for beginning metal-casters.

I'm entering this in the Epilog laser cutter challenge, so if you like it (as if you couldn't), please vote.

I'll be your best friend ;)

Step 1: How This Is Green

Picture of How This Is Green

Before I instructify your minds, let me tell you how this project is green.

I live in Hattiesburg, Mississippi, and in Hattiesburg there is no recycling center. The nearest center is in Jackson, Mississippi; which is about 80 miles away. Nobody wants to drive 2 hours just to turn in some cans they could have thrown away in 5 seconds.

That's where me and my friends come in.

Our friends, family, and even random people who just want to recycle bring us pounds of aluminum cans each week, which ordinarily would just be taking up space in a landfill.

We melt down their trash to create tools or art, which we then can either sell or give away.

And though this foundry design pollutes the air with smoke and fumes, it teaches us (and any other beginning metal-caster who wishes to learn with us) what we need to know to build greener, more efficient designs which run off of clean-burning propane or use waste-oil as the fuel (reducing the amount of toxic chemicals people would be dumping elsewhere).

As we learn how to build cleaner, more efficient foundries, I will post instructables, so people in places like Hattiesburg, MS, will be able to do their part to save our planet.

On to the legalities!

Step 2: Legal and Precautionary Statements.

First off, this instructable deals with fire, molten metal, sharp edges, electrical equipment near water, burning paint/other noxious fumes, and probably some other dangers I don't even know about. If you are a clutzy, hyper, or unattentive person you really shouldn't try doing this.

By reading this instructable you agree that I am not liable for any of the numerous injuries you may incur, property damaged, people harmed, or anything else you could think to sue me over, while building and operating the foundry described within said instructable

That being said, If you follow my instructions you should have no problems with safety. I will do my best to detail the safest way to do this.

Step 3: Read Up. Arm Yourself With Knowledge

Step 4: Materials and Tools.

Picture of Materials and Tools.
I built my furnace for nothing, and you can too if you borrow some tools and swipe some trash.

Required to build furnace

  • Drill with large bit suitable for steel. (Hammer and large steel spike can be substituted)
  • Tin snips

  • 2 coffee cans of equal dimensions (one for furnace, one for air chamber)
  • 1 hair dryer with a cold air setting
  • 1 tin can (Blue Runner bean cans are the perfect size and are very strurdy)
  • At least 4 metal stakes (optional)

Required to operate furnace

  • Instant light charcoal
  • Charcoal lighter fluid
  • Barbeque lighter (the long-nozzled kind)
  • A bucket of water (to cool hot tools)
  • Aluminum cans
  • 3 or more boxes (optional)

  • Tongs (I use 2 pairs)
  • Some sort of long, metal stick

Safety gear
  • Leather gloves (preferably welding)
  • 100% Leather and/or cotton upper torso/arm coverings (Big Smith jackets are perfect)
  • Gas mask (optional, you can just hold your breath when near the furnace)

Required to make mold
  • a large container
  • sand
  • Something to impint a design in sand with or way to draw in sand (pottery, carvings, body parts

Step 5: Building the Air Chamber

Picture of Building the Air Chamber

Use your tin snips to cut a hole in one of the coffee cans for the hairdryer to fit into. It's O.K. if there are some corners that don't quite conform to the hair-dryers nozzle, mine don't and my foundry works just fine (See pic 2)

Step 6: Building the Fire Chamber

Picture of Building the Fire Chamber

Using your drill (or hammer/spike combo) make holes in the bottom of the other coffee can. Again uniformity is not a requirement.

Step 7: Assembling the Furnace

Picture of Assembling the Furnace

There is a simple way to do this-

1. Insert hair-dryer into air chamber
2. Put fire chamber on top of air chamber

-Which is easy as pie but extremely dangerous. If the fire chamber is nudged even the slightest bit the whole thing will topple over, creating a gauntlet of hot coals and molten metal at your feet.

On the other hand though, being able to remove the fire chamber from the furnace gives you the advantage of being able to shake out the coal dust that will eventually clog the holes to the air chamber. This allows you to keep the fire burning hot longer for multiple melts.

If you feel you can't handle having the fire chamber loose, than you should dig a fire pit, fill it with sand, and put metal stakes in the ground running along the sides of the cans. This will hold the cans in place but still allow you to quickly remove the fire chamber.

Step 8: Destroying Your Aluminum Cans.

Picture of Destroying Your Aluminum Cans.

It is important to seperate the parts of the can, as they all produce different amounts of dross (trash in the metal which has to be removed), and should be melted at different points in each smelting.

The 3 sections which have to be seperated are the top, the sides, and the bottom of the can.

My favorite method for destroying the cans is illustrated in the pictures. Unfortunately, I can't get the image notes to work, so you'll have to read the procedure up here and follow along with the pictures below.

1. Cut or rip the can in half.
2. Make a slit in the top half, perpindicular to the lid.
3. Tear along the slit and pull the siding off of the can top.
4. Make a slit in the bottom half of the can, at an angle to the bottom.
5. Tear as close to the bottom as you can, and remove siding.

This goes much faster if you form a production line with some friends in which one person has one of the steps above assigned to him/her.

I sort the cans into boxes of halves, siding, tops, and bottoms, with the occasional box for cans with painted tops or bottoms.

Once you're done with your cans, it's time to ready your foundry.

Step 9: Laying the Coal.

Picture of Laying the Coal.

With the furnace assembled, place a ring of coals around the bottom of the fire chamber (pic 1), Then place two coals perpendicular to the ground in the center of the ring, leaning against each other (pics 2+3). This increases airflow under the can, which helps to heat all the coals and ultimately provides a better melt. The wrong way to do this would be to put one coal flat under the can, (pic 4) blocking airflow from the center of the furnace.

Next put the tin (steel actually) can on top of the two central coals and add coals evenly to the sides of the tin untill it stands on it's own.

Step 10: Making the Mold

Picture of Making the Mold

If you don't want to make a mold, just some metal blobs (ingots), you can pour the molten aluminum into a muffin tin. The ingots can be re-melted later if you need the metal.

Making a sand mold is easy. All you need is some sand and a way to imprint a design in it.

You could do this with a stick or something, but it probably wouldn't turn out well. I find you get the best results when you use something with a 3-D pattern on it. In this instance I used some pottery, I found at the flea market.

If you have a friend (or friends) working with you, they could make a cool design, while you melt the metal.

Now all that's left to do is prepare your work-space.

Step 11: Foundry Feng-shui.

Picture of Foundry Feng-shui.

There are a million possible misfortunes waiting in a foundry, and you can eliminate almost all of them by being prepared.

I have here some pictures of my foundry set-up and running, as well as some pictures of me operating it.

Notice that the cords are held away from the walkspace with a bucket so I won't trip on them, and that the water and aluminum (i.e. conductive materials) are on the other side of the walkspace.

You need to be able to walk in a complete circle around the furnace without bumping into anything.

The water and mold need to be where you can reach them quickly when you need them, but not so close to you that you bump them.

If you've done all of the above, it's finally time to start up you're furnace!

Step 12: Starting the Furnace. (FINALLY!)

Picture of Starting the Furnace. (FINALLY!)

Make sure all your safety gear is in place and then get ready to finally do some metal-melting!

First load your crucible half-way full of can tops, they burn the cleanest, so burning them first yields more molten aluminum to submerge other can parts in.

Then, light the charcoal!!! Whoooo! fire!

If you use regular charcoal, you have to use lighter fluid, which can drip through the furnace onto the hairdryer, for this reason I only use coals that light instantly in my furnace.

As soon as you think all the coals under and around the crucible are lit, start the hair-dryer.

Next you need to add coals to the side of the crucible untill they form as even a layer as possible around it's center.

Once the can tops start to melt and you can see the can glowing red it's time to move on to the next step.

Step 13: Operating the Furnace.

Picture of Operating the Furnace.

I had several instructional videos to show you, but my mother managed to unintentionally delete them off of her camera.

The world weeps.

It's O.K. though, operating the furnace is pretty straight-forward.
All you really need to do is

1.Fill the crucible of aluminum scraps
2.Cool the tongs in water
3.Let the aluminum melt
4.Use a metal pole to remove dross (Gross stuff floating at the surface)
5.Cool metal pole in water.
6.And repeat

If you don't have a gas-mask then you need to hold your breath when you feel hot air from the furnace hitting your face

Aluminum scraps should be melted in this order; can tops, can bottoms, and then can sides.
This is in order of metal-to-dross yield.

Dross should be removed quickly after the aluminum melts, or else it will clump together with some of the aluminum and stick to the sides of the can, reducing the amount of pure aluminum you can get per pour. There are some pictures of me removing dross below.

Also you must be careful with hot tools, not only because they can burn you, but because they can burn other things.

For example, If you use hot tongs to try to grab coal out of the coal-bag, the coal could ignite setting the entire bag aflame.

When you notice that the crucible's glow is starting to fade, either add more coal to the fire, or prepare your mold for pouring.

Step 14: Pouring the Mold

Picture of Pouring the Mold

The most self-explanatory step. Pick up your crucible with your tongs and pour the molten aluminum into your mold.

The aluminum has a smooth look to it's surface while it's still molten, but if you watch closely, you can see it start to crystallize.

Try not to pour from too high or the aluminum will crush the detail out of the mold.

Again, I apologize for the lack of videos, I'll try to upload some soon.

Here's a pic of the finished product. (I didn't use enough aluminum) :(

Step 15: Come On...

...lets be honest with ourselves, you know you loved this instructable, I know you loved this instructable, we both know you loved this instructable. So why are we playing this game? Stop playing coy and vote for this instructable!

Seriously though, the laser cutter would be put to good use.


leungalb (author)2017-08-13

By far the simplest instructions on melting and casting aluminum that I have seen. Thanks for the great work!

Akrylamid (author)2016-07-14

Thinking about the molds... Would a mold made of JB Weld be able to withstand melted aluminum?

trigger ects (author)2012-08-02

what sand did you use and how much water do i put in the sand

TomOlsen (author)trigger ects2015-11-12

I am going to use "Paver Sand" from Lowes. It is a fine grain sand which seems to pack better than their normal "Play Sand". I will also add some clay dust made from unscented & unclumping kitty litter to improve the packing properties.

TomOlsen (author)2015-11-12

Crucible: I use one of those "squatty" propane bottles from a propane torch that I filled with water and then cut with a metal cut-off blade in my skill-saw. It is plenty big enough to hold aluminum cans, and so far it has lasted 6 firings without signs of needing replaced. I did try to weld some handles on it, but I ended up burning a tiny hole near the top so I gave that up and just use a large pair of channel lock pliers to lift it out of the furnace. I made my furnace inside a 6 gallon bucket with a small plastic trash can (about 2 inch gap between them) and filled the gap with 50% Plaster with 50% sand mixture. The plastic trashcan burned out the first firing except a layer in the bottom that I pulled out after it cooled. I then drilled a 1 inch hole going into the bottom where I inserted an iron pipe. On the other end of the iron pipe I put a 90 degree elbow and feed it air from a slip-joint PVC pipe setup of 1-1/2" PVC inside 2" PVC then an old hair dryer as the blower into the 2" PVC. I could have Duct Taped the PVC but I like the slip-joint for positioning. The hair dryer has a "cold" selection and then 2 air speeds. Bought it at Goodwill for $4. I also made a top out of the lid, but it is starting to flake off on the inside. The lid keeps the heat in better and everything works faster. I use welder's gloves to remove the lid (with the blower off) and to handle the pliers as I pour. I am still experimenting with ingot molds. So far my best results are from a steel mini-muffin tin. I plan to make my metal molds from "Paver Sand" mixed with clay dust (made from unscented/plain cat litter) and pack it into frames to make impressions of my items to be molded. Here are some of the pictures I took.

TomOlsen (author)TomOlsen2015-11-12

During operations the blower pipe is not inserted inside the burning chamber, just up to the charcoal. Light the charcoal and after it is lit for a while turn on the blower at low setting. After charcoal is well lit turn up the blower to high.

man ray (author)2009-06-10

what did you use for a crucible?

Fenris The bbw (author)man ray2009-06-22

A tin can.

Wyle_E (author)Fenris The bbw2009-08-04

That was certainly a steel can. BTW, I've seen a lot of aluminum soup cans lately. They usually have pull-tab tops. Before you use a food can for a crucible, check it with a magnet. The best cheap crucible for aluminum and zinc alloys is a short piece of steel pipe with a piece of steel plate welded over one end. I haven't checked with local welding shops, but it would probably cost less than the cheapest clay-graphite crucible from Budget Casting Supply. There are a *lot* of web sites devoted to amateur foundry. www.backyardmetalcasting.con is a good start.

Fenris The bbw (author)Wyle_E2009-08-06

I think i adress that most cans are made out of steel somewhere, but for the life of me, i can't figure out where. Probably in the comments somewhere. Also, a welded crucible would probably work better, but I'm trying to make this build as simple as possible so others with no experience can replicate it.

JohnnyC27 (author)Fenris The bbw2015-10-09

what is your mold made of?

Have you ever tried a ceramic crucible? I was wondering if you would get a purer product if you didn't have the ferric metal possibly alloying minutely with the aluminum.

A ceramic crucible would be awesome. But I'm trying to keep it cheap and only use garbage for my materials.

Also, I don't think the steel alloys with the aluminum at all, but rust flakes might get in the melt if you use the same crucible more than once.

leifbus (author)Fenris The bbw2010-05-18

 Could you make a crucible out of plaster? (since you could cast the aluminum into it anyway?)

Wyle_E (author)leifbus2010-05-26

Plaster, like portland cement, sets by a hydration reaction.  Get it hot enough and it dehydrates, turning back into dust.  The furnace is going to be a lot hotter than a mold full of molten metal.

Can you use a glass bottle or container as a crucible? I know it has a much higher melting point than aluminum and is somewhat easier to come by than steel.

The short answer, no.

The long answer no becuz it'll explode, or at least crack, which would waste all the aluminum.

ThatCatMan (author)Wyle_E2014-10-21

I am not sure if it would be any good as a crucible but WalMart sells stainless steel cups with handles for camping for like, I think $9.

bshelton4 (author)Wyle_E2011-09-11

I can make you some stainless crucibles if you would like or carbon steel. I take paypal so you are covered and ship USPS.just need to know the size and what kind of material you would like. 256-309-9406 is my number. Thanks.

skatattookid (author)man ray2013-04-24

my crucible was an old fire extinguisher that i cut the top off with a sawsall. works great!

Ph3tdart@ (author)skatattookid2015-01-25

Were did u get a fire extinguisher made of steel? Cuz everything is made out of Aluminum now!!

MichaelL63 (author)2015-08-10

Here are a few photos of success in action

mcampbell19 (author)2015-06-24

this is just plain awesome....

nicklowe86 (author)2015-04-05

what a great idea, for a number of reason. skys the the limit with what you could make with this stuff

Nat A (author)2015-02-10

awesome me and my friend need to make something like this :)

ykohavi (author)2014-11-03

Made it and it worked! Make sure to have enough coals, start by putting a small amount of metal first and wear protective glasses

Gilderod (author)2014-08-03

Excellent instructable!

Mr.Brownstone (author)2013-08-17

that is cool. I might try that.

jadronx (author)2013-05-21

Wonderful instructable! Aside from the lack of face shield that is. I am excited to see what new designs you come up with.

jbend (author)2011-07-02

can you use wood insted of charcoal.

letstormdufield (author)jbend2012-08-21

No, Wood will not burn hot enough

wood does burn hot enough. i do it all the time.. in fact thats all i use to smelt my aluminum. granted you use alot of wood but if your like me and you have alot of trees on your property then its no problem.

farmboy15 (author)jbend2012-09-18

Yes you can i have used wood alot just cut it into kindling then it will turn into hot coals quickly which are easily able to produce the heat required for melting aluminium

rsmigielski (author)2013-01-05

what kind of gas mask filter will cleanse the toxic fumes form the cans?

brsild (author)2012-10-21

is there a way to set it up to melt stainless steel?

trigger ects (author)2012-08-01

im going to make this just got to find the coffee tins

Wiredfey (author)2012-01-07

Question,i have a heat gun which i use to take off formica when doing remodel and use it to melt ice. would this be more effective?

Fenris The bbw (author)Wiredfey2012-02-09


Hot air is less dense than cold air, and consequently contains less oxygen.
I know it's counter-intuitive, but colder air burns better.

Wiredfey (author)Fenris The bbw2012-02-09

that's kind of funny but interesting :) thanx,time to hit up a goodwill for a dryer.

Deadskull57 (author)2011-08-25

Cool, I've been looking for a good foundry instructable, looks like I'll be taking a trip to the goodwill for a cheap hairdryers.

TimmyMiller (author)2011-06-18

what if you just removed the paint from the cans?

canis (author)2009-06-03

cannot stess the importance of a face mask here. no matter how well prepared you are, unexpected s#!+ happens. a cheap lexan face mask from a local welding supply is a lot cheaper than skin grafts - and a hell of a lot less painful.

canis (author)canis2009-06-03

P.S. i got my degree i bronze casting specifically, and i have a ton of experience with all manner of aluminum casting. i know whereof i speak.

Fenris The bbw (author)canis2009-06-04

Thanks for the advice. You can get a degree in casting? That's awesome, I'll have to look into that.

canis (author)Fenris The bbw2011-04-28

Not bronze casting specifically, no LOL. But bronze was my emphasis in my sculpture degree, which is as close as one gets, I suspect.

junits15 (author)2009-09-24

put a rol of pennys in, they if its hot enought, they will burn blue.

trknust (author)junits152011-04-24

DO Not do this with pennys. This can hurt you fast. Most pennys now are made out of Zinc and will poison you if you breathe the fumes when it is melted or burning.
They have a very thin coating of copper over the zinc cast.
If you want to melt copper, use old copper tubing or wire with the plastic removed. Just make sure it is realy copper all the way through.

And to prevent oxidation a little bit of hundred mule team borax floating on top works like a champ.

Firestorm_101 (author)2010-09-29

How do you make 3d designs like ring, bracelets, bangles, etc? Could you put a material within the sand with a gap uptop, that would incinerate immediately while pouring in the molten liquid?

there was a show were they would see which of two animals would win if they ever got into a fight. i loved the show, not only because of the awesome idea, but because they always made a black iron replica of said animals skull (complete with teeth) or claws or what not .... ON THE SHOW. they even exsplained what they were doing.

they would pretty much do sand casting, however they would use foam, like styrefoam, that they carved into shape, and just pour the molten metal onto the sand. i don't think they even made sprue. of course, i think they used iron sand..... may be important....

the downside to this is that the metal was kind of pitted.

neorazz (author)badideasrus2010-11-14

i remember that show they would overcast the teeth and then polish them down to size i though them to be unrealistic in comparison to the same size tooth in enamel/bone (much higher psi before breaking) but the metal work idea is sound if your making your own foam molds enlarge them a bit then you can machine off the excess for a good finish where you need it

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