I am looking to make a smelter for smelting aluminum but I have a limited budget and I would like to smelt large quantities. I am guessing probably 6kg per use but more would be better. I have been thinking about creating an induction smelter that uses refractory bricks that can be used repeatedly and creating it by using 2 microwave transformers hooked up to a copper coil. I am not very good with electronics so what do you guys recommend for a smelter design. Please get a parts list for the design so I know the cost.

You can check out the Gingery Machines group on yahoo-

Lots of discussion on diy smelting of aluminum. I understand there is quite a bit about it to be found on youtube also.

You may want to look up how to make an electric forge/casting furnace on YouTube. I’m not sure what you would need the transformers for.

You will likely need access to 240VAC.

This is a dangerous endeavor, so be sure to read the safety protocols and buy the appropriate PPE.

?Smelting is getting aluminum from ore. I think you want a “foundry?” to melt and pour cast aluminum?

Google ‘aluminum foundry’ you’ll find many many hits. Videos too.

If I were doing it and wanted it as large as you say, I would make one from two propane-tanks end-to-end that have been sawed, filled with insulating cement.

I would use propane for the fuel, probably just buying a ‘weed burner’ and sticking it in a pipe. Seems alot less risky than using microwave transformers.

I would saw-off a 10-kg fire extinguisher for the crucible.

I’d buy tongs and tools online.

If you intend to make shapes, you’ll also need to buy casting sand and figure out molds and sprues. Ref, I’ve read that you can actually 3-d print plastic to sacrifice and pour sand cast aluminum to those shapes.

This guy has the info you need. Just make sure the fire extinguisher is steel tank, not aluminum.

Please avoid playing around with MOVs (microwave oven transformers) if you don’t know what you are doing. I’m not the overly cautious type but those things can seriously mess you up if you don’t have an understanding of AC mains power. Stick with a gas powered burner, it’s a tried and true solution and you will be far more likely to end up with a reasonably satisfactory result.

I built a foundry out of a propane tank, it ran about $75-100 to make. That doesn’t count the crucible, tools and safety gear. If you do decide to make one, please be very aware it can be dangerous.

How not to pour Aluminum

The key take away from that video, is that the mold looked dry. Realize that water expands 1,700x going to steam. Imaging what .5mm drop would mean.

A common source people use for aluminum are soda cans. So you put a soda can in the foundry. A can that you can’t really see what’s in side, that is used to hold liquid. It can easily have an explosion when adding the can.

Finally, the crucible is important, I didn’t follow any of those “DIY” suggestions. Last thing I want to worry about is if this thing is going fall apart when I’m moving molten aluminum. I spend $100 on a nice 10lb capacity one

As you can see, it can get really bad in a few milliseconds. If you and the people around you have healthy respect for safety procedures, it can be a fun thing to do.


Might be nitpicking a bit, but this statement is kind of misleading/nonsensical - a gas doesn’t have a fixed density, and so once water goes to steam it doesn’t take up a fixed volume. Even if this number was calculated assuming a temperature of 100C and a pressure of 1atm (seems like the most reasonable approach), it’s still pretty misleading.

Grant Thompson(The King of Random) has some videos on making one of these devices:

Mini Metal Foundry (Watch this video before building one)

Propane Fuel Version of Mini Foundry

Larger Foundry

Speaking of fire extinguishers, keep a working one nearby if you do actually build one of these.

If you had a droplet of liquid water under the surface of the melted aluminum; it would become superheated steam and take a finite volume until it could reach the surface.

If you think of the ideal gas law, PV=nRT, where n= mass/Molecular Weight. Rearranging you can solve for density as m/V=(MW)*P/RT, thus an ideal gas does have a fixed density at any given state.

For water there are readily available steam tables.

Room Temp Liquid water has a density of 1000 Kg/m^3
Superheat steam at 1 atmosphere, and the 1221° F aluminum melting point has a density of 0.2506 kg/m^3.

Since we’re interested in volume per unit of water mass…

Take the reciprocals of density and dividing (1/.2506)/(1/1000)=3,990 times expansion.

Note that the expansion number you gave is more than a factor of two different from what was stated in the post I responded to, which appears to have been calculated at 100C.

Simply stating an expansion factor hides the assumptions you’re making when calculating it, and is thus potentially misleading. At worst, people forget that there even are assumptions being made.

Dry Steam at 100° C has a density of 0.597518 kg/m^3

That would yield a ratio of 1673 or 1700 rounded. His statement was for “water going to steam”, so this number is correct as stated.

I simply pointed out Melted Aluminum is significantly hotter then 100°C. The effect is the same, spraying melted aluminum is bad.

I think you’re missing my point - the fact that the expansion factor was correctly calculated under certain assumptions doesn’t change the fact that simply referring to it as a rule-of-thumb hides those assumptions (which may indeed fail in the situation you’re trying to describe). It’s somewhat dubious to simply tell people that “water expands by a factor of 1700 when turning to steam” - such a simplification is fine if you understand where it come from and when it might fail, but not every reader will know that.

I don’t think it’s reasonable to expect the average reader is going to understand the details of college level thermodynamics, and all the possible states of steam. The simple understanding that liquid water expands substantially (1000X plus) when changing to the dry steam state is the important concept.

A reasonable rule of thumb is often useful in the gaining a basic understanding how systems operates. Perfection is the enemy of good enough.

I wouldn’t call the ideal gas law “college-level thermodynamics.”

The concepts of Enthalpy and Entropy and their application to state change are. The ideal gas law doesn’t cover liquids or their vaporization to gases.

You stated above
" Might be nitpicking a bit, but this statement is kind of misleading/nonsensical - a gas doesn’t have a fixed density, and so once water goes to steam it doesn’t take up a fixed volume."

Gases do have a fixed Density or mass and Volume at any given Pressure and Temperature. Continued debate on this point is not productive.

The problem’s still there - molten aluminum has a surface tension of 1.007 N/m [1]. Say we have a 0.05 mL (0.00278 mol) drop of water. Container is 30 cm in diameter and 10 cm tall (full to the top). That means there’s .00707 m^3 of molten Al - works out to 16 kg of Al (right order of magnitude for the 10 lb estimate) [2]. If we take surface tension of Al into account along with this weight, that works out to 160.2 N pushing down on the steam.

Now, the steam. Steam at 1221 F (660 C, please) has density 0.2506 kg/m^3 at 1 atm. Assuming this steam will be in a spherical shape (Vol: 4/3pir^3, SA touching Al: 4pir^2), we can calculate the pressure and volume of the gas.

P = (160.2 N)/(4pir^2)
V = 4/3pi
P = nRT/V nRT is a constant in this case, so rewrite as:

25.46/r^2 = 10.27/r^3
r = .403 m. Hmm looks a little big. Well, the steam’s gonna expand fast regardless - so watch out. If anyone can find anything I did wrong (probably did), please tell me.



$@#$@#$@#$@# google. I didn’t want to swag a number, so I did a quick search. #bonjour

The absolute pressure on the water droplet / steam is simply the weight of the aluminum column above it (hydrostatic pressure) plus atmospheric pressure. The surface tension on a 30cm diameter container will be a minute factor.

Assuming sea level std day atmospheric pressure, and the drop is in the middle of the container.

P=(AL density) * g * height + 101325 Pa
P= 2375 kg/m^3 * 9.81 m/S^2 * 0.05M + 101325 Pa
P=1165Pa + 101325 Pa = 102490 Pa or (N/m^2)

Thus the pressure is really only 1.0115 Atmospheres, close enough to 1 Atmosphere.

The proposed 0.05ml water droplet is equal to 5E-8 m^3 of volume

If we use my previously shown expansion ratio of 3990 from liquid to steam at 1 atmosphere; the volume becomes
V=3990*5E-8=0.0002 m^3

Assuming a Sphere: V=4pir^3/3, then r=0.0363 m or 3.6 cm

Thus a single water droplet becomes a 7 cm diameter sphere of steam; which could blow a lot of the molten aluminum out of the container.

What do you guys think about this version (BTW if I made it i would modify it to prevent shock from the coils):