Quick and Cheap Aluminum Melting Furnace Setup

Introduction: Quick and Cheap Aluminum Melting Furnace Setup

About: Dad and hubby, good food enthusiast, solar energy, boating, making stuff, melting stuff, and raising chickens.
This Instructable shows a quick and cheap setup to melt a few batches of aluminum for casting before the thin metal equipment starts to break down. Actually the 5-gallon bucket furnace will last quite a long time, over a dozen uses easily. This uses BBQ charcoal as the fuel and a hair dryer as the blower, it'll melt a small batch of aluminum in about 10 minutes. Most of the materials to build this can be found in dumpsters; the only cost here is the charcoal fuel, duct tape, and the $1 yard sale hair dryer. Recycle old lawnmower parts, computer/stereo parts, and beer and soda cans to make awesome new things with them.

For the furnace, two five gallon metal buckets (with lids) were used, a piece of 3-inch stove pipe, hair dryer, and of course, some duct tape.

For a crucible (the little bucket that holds the melted metal), a 16 oz propane bottle was used; the top was cut off and some bolts were added for grabbing the crucible with the tongs.

I made some basic tools with some scrap steel from an old bed box spring. You'll need tongs for the crucible, some kind of shepard's hook to tip the crucible when pouring, and a plain rod with a little bend at the tip for poking things and skimming out the dross (impurities in the aluminum).

Use of this equipment shown is dangerous because of very high temperature molten metal, fumes and smoke, etc. Use caution and be safe by wearing leather gloves, face protection, and other protective clothing. Do this outdoors and use it when it's a little windy so the smoke and fumes quickly dissipate, also use this during dry conditions because dripping molten metal on wet surfaces can cause little hot metal explosions (like water and hot oil in the kitchen). I'm not liable for any injuries you may occur using the equipment and techniques shown here.

Read, read, read lots of metal casting stuff before starting.

Casting Aluminum at submarineboat.com
Home Foundry
BackyardMetalcasting.com ...Melting and casting metal yourself

Here's a silent movie of the foundry at work.

Step 1: The Furnace

Using tin snips, cut a hole in the bottom side of one of the buckets to fit the 3 inch diameter stove pipe.

The hair dryer needs to have the "cold" button taped for use as just a blower; tape the hair dryer into the stove pipe, then insert the pipe into the bucket . Air flow is the most important part of this, I first used a little 1.5 inch pipe, but it just wasn't enough air volume to get the charcoal really nice and hot.

The bottom of one metal bucket is cut off about 2 inches from the bottom; a lot of holes are punched in center 6 inches of that piece and it's inserted into the main bucket as a burning base.

Keep the lids, one lid should have a 3 inch vent hole in it for burning and the other lid should be left unchanged for snuffing out the fire.

Step 2: Crucible

This crucible might last half a dozen uses, but it's cheap and easy enough to make several of these.

Use a hack saw and cut off the top of a little camping propane tank (make sure its empty first).

Drill holes near the top of the cut tank for inserting some large bolts; these are for picking up the crucible.

Use a hammer and knock a pouring lip into the edge of the crucible.

Step 3: Tools

Tools, to make them you'll need a bench vice and some gorilla power bending skills. Just bend until things fit nice. Use something other than aluminum, like steel rod or conduit pipe.

These are the tools needed:

  • Hook tongs for lifting the crucible by its bolts.
  • A shepard's hook for tipping and pouring the crucible
  • A dross stick for skimming out the metal impurities.

Extra tools to have handy are:

  • Grill tongs
  • Large adjustable pliers

Step 4: Safety and Use

  • Wear leather gloves, long sleeve non-synthetic clothing, preferably leather and thick cotton and leather boots, no flip-flops no matter how fun it sounds to have a hole fried into your foot. Also a hat to keep embers out of your hair.
  • Have a garden hose charged and ready for fires.
  • Work over dry dirt.
  • Have something ready to pour into; a mold in green sand for casting or regular dry sand when foam casting; many backyard casting people use steel muffin molds to make nice little ingots.
  • The first use of this is the stinkiest because of all the paint burning off the bucket and crucible, after that it's not so bad. It's best to do this on a slightly windy day.

To operate this, fill the furnace 1/3 full with charcoal and light it like you're going to cook some hot dogs. Wait until the coals start to turn grey on the edges, now fire up the blower and set the crucible in there with chucks of the aluminum. Cover the furnace with the vented lid, then grab a chair, a drink, and wait. When the aluminum is liquid, skim the floaties off the top with the hooked metal rod until the molten aluminum looks like a shiny pool of mercury. Now it's ready to pour.

Have all the safety gear on, turn off the blower, remove the lid and use the tools to grab the crucible and pour.

In the picture below, all my sand got wet just before I wanted to melt some metal, so I used clay kitty litter for a quick lost foam casting test . I don't recommend kitty litter; see all the lumps and pieces still stuck in the cast. Lost foam casting is using a piece of shaped styrofoam stuck in dry sand, then pouring in the molten metal which burns out the foam and takes its place.
Lost foam casting at submarineboat.com

Have fun, I know I love it and will probably make a higher quality setup sometime.



    • Metalworking Contest

      Metalworking Contest
    • Fix It! Contest

      Fix It! Contest
    • Tiny Home Contest

      Tiny Home Contest

    87 Discussions

    You can make a longer lasting backyard foundry using a metal trashcan (I think it is about 20 gallons) for an outer wall, a metal 5 gallon bucket for the inner chamber, cheap unscented Kitty Litter (it is made of clay) to fill gap between outer wall and inner chamber (mix with water so it will pour like concrete, let dry thoroughly before using), some pipes and a blower for forced air, and an empty propane torch canister (make sure it is totally empty, fill with water & empty before cutting it to use as your crucible!), and charcoal as your fuel. You can scale this down, use the 5gal bucket as outer wall, large coffee can as inner wall. Just remember: Injuries from molten metal are PERMANENT! Molten aluminum can burn right through normal clothing and through your leg. So, BE CAREFUL! Do some Practice runs using sand as your "molten metal" so you are not surprised by the weights.

    1 reply

    Super easy and cheap Aluminum can forge.

    I made one with a thicker concrete crucible and it didn't work. for a couple of hours it withstood the heat from a large bag of charcoal and a lid to trap the heat. mail came at that time and i threw the junk mail in and in a couple of seconds the junk mail burst into flames. i think my problem was a thick concrete crucible. will use an old fire extinguisher next time.


    2 years ago

    How'd you cut the hole for the stove pipe so neatly? Mine ended up being a jagged mess with a big gap when I put the pipe in. Also do you permanently attach it any way? (Like with glue or something.)

    1 reply

    Draw the hole with a sharpie using the pipe as a template; then drill in the middle with your best bit. Use tin snips to cut pizza slices from the middle hole to the stenciled edges. Bend in the pizza slices and use them to attach small self tapping screws if needed.

    this is exactly what I was looking for!....cheap, easy to build and disposable!
    until I found your instructable, everything I had found online was way too elaborate for my first run at this.
    I am beyond excited, I cannot wait until later this evening! I spent last night tearing heat sinks off some old PCBs that came out of old stereos, dvd players and VCRs (great source for aluminum.)
    great write up, btw...appreciate the advice/reminder on wearing PPE.
    I'll let you know tmrw how it goes!

    1 reply

    I'm glad this will work for you. My only recommendation is to add some type of insulation; the heat loss is high but tolerable.

    Loved your 'ible but didn't understand (or missed) the purpose of the second can. Am I right in my thinking?....starting from ground up - bottom of large can/barrel, next a void into which the blower system is inserted, next the smaller can with holes in the bottom, next the coals and the crucible? Or does the charcoal go between the 2 cans along with the blower and the crucible sits on the bottom of the smaller can?
    Also, do you skim the top of the molten liquid thru the hole in the barrel lid or do you remove the lid? I'm trying to imagine trying to see what needs to be removed while looking directly at a brightly glowing fire and around my gloved hand and the skimmer!
    PLEASE (everybody) forgive my ignorance, but we all have to start somewhere!

    1 reply

    The charcoal burns on a little shelf made by the second bucket (with holes drilled in it) upside down inside the main bucket; the air blows in from under the charcoal.

    The crucible nests in the charcoal.

    I remove the lid when working with the molten metal; if it looks like floating 'dirt' on top of the liquid metal, that gets skimmed.

    Good luck

    okay, once the aluminum is melted.. what can I pour it into for a bar shape?..that will put up with heat and keep its shape.. and I need to know a little on the cooling process, as in when it's safe to grab and such.

    2 replies

    Well then. You'd just get steel or something else with higher melting temperatures. Typically you see people just using a stock bar imprint of steel or little nugget molds.

    can plaster of paris mould be used to cast this moulten aluminium into?.....i would imagine they would deteriorate rapidly due to the heat...anyone know any adjuncts to add to plaster of paris to increase its heat resistance/durability....oh and if you try using plaster of paris make sure it is well and truely dry.....kaboom otherwise

    1 reply

    Don't use plaster of paris - it will not hold up at all. Plaster of paris, mixed with sand, is fine for a temporary refractive material for the inner lining of a furnace but liquid aluminum will go right through it upon contact. If you absolutely need the fine-grain resolution that a plaster mold would give you, consider silicon or even very fine green sand.

    How can I make a furnace to work on a larger scale? I am talking about having enough aluminum for large projects ( at least 16"x20"x18") but some projects are larger. The small one just won't last long enough or melt enough metal at a time.

    1 reply

    That's a lot of aluminum, make sure your furnace is actually hot enough to make sure the center of the aluminum is as hot as the edges! Suggestions to break a larger project into smaller ones would be making aluminum chunks that fit into each other through a series of tight bars and meshes. Or when you cast them you can add a center to your mold so the aluminum makes a thick shell around the outside (your required strength) but you save tall the aluminum that would've been in the center.

    and what did you use for the bolts on the old camping propane tank, and how did you cut it open.