Aluminum Furnace Upgrade 

Awww man! Building the furnace is half the fun!

Let your spoon heat in the Al for a couple seconds to help it not stick to the spoon

Great to see another video. Looking forward to watching this one.

Waited for 4 years. Finally!

Wouldn't have Been easier to just sit the pan on top of the furnace for a minute to burn it off.

I like your videos and glad that you are back

Al conducts heat very well and so its temperature profile while casting is comparatively flat. The result is that it freezes really suddenly at a high thickness. With cast steel you end up with a solid skin and molten interior. With Al it solidifies right to the core. This makes pouring etc more difficult. You need a significant overheat to handle it easily.

Nice little furnace.

YAY NEW VIDEO!

When I did a bit of this I had real problems with using soda cans. Instead I got scrap extrusion aluminium from wrecked engine blocks very very cheaply. Mixing some of that in might help fill out the muffin pans. You could possibly pre-burn the paint and plastic liner in an oven or barbecue which would reduce bubbling from hot gases, helping to keep the surface area down.

Based on my experience (I recently built a very similar furnace and am melting with it aluminum, copper and making aluminum bronze and tin bronze) I see a couple of problems with your equipment. It doesn't appear that the bottom of your furnace is covered with insulation. Also the kaowool performs much better if it's covered by another refractory layer. In my build I used 2400-degree rated kaowool (1 inch) which I then covered with 2 layers of a refractory clay called satanite (rated for 3200F). I mixed the satanite with water to the consistency of thick sour cream then brushed it on the surface of the kaowool about 1/4inch thick, let it dry for 1 day, warmed the whole furnace with a heat gun inserted through the burner orifice for about 30 minutes until it was nice and toasty to cure the first layer. After it cooled down I applied a second layer then dried and cured it the same way. It is holding together beautifully. I have done about 10 runs with it melting copper and making bronze at temperatures above 1100 degrees Celsius and there isn't even one crack in the coating. Uncoated kaowool will begin to melt at the surface and sag after a few runs. Not to mention put out small ceramic fragments in the air that you breathe. Don't forget that the lid needs to be coated too of you decide to do it (which I highly recommend). I have also coated the exterior of some of my clay graphite crucibles with 2 layers of satanite. Compared to uncoated crucibles, the coated ones are holding together much better. Use a flux when melting metal. For copper and bronze, borax works best at about 1 teaspoon per pound. For aluminum I use a 1:1 molar mix of NaCl and KCl (58.5g NaCl and 74.5g KCl). The mixed salts form an eutectic with a lower melting point than either, at about 600 degrees C which is just below the MP of aluminum; it will make the dross easier to manage. And you do get a lot of dross from cans. Lately I've been melting mostly pieces of cast aluminum and get far less dross from that. (Edit) I've looked at the pictures on Amazon and the bottom is insulated. It just looks in the video like it's bare. Maybe it's because I watched it on my phone instead of a computer.

Flux and a degassing agent could help, a quick googling indicated 50% NaCl 50% KCl ("lite salt") for the flux and bubbling nitrogen through the melt for degassing. Apparently the burning propane and plastics will dissolve hydrogen into the aluminum.

Some tips: Keep the tabs on the cans. Heat your spoon/drossscraper before you scrape to waste less Aluminium. Just stick it in the pot and let it sit for a litte while before scooping the dross out. Keep the temp up for easier pouring.

Drinks cans are pretty much the worst possible source of aluminium for casting (as you've found :) ), the coatings are a significant part of the weight and the mostly pure aluminium shrinks a lot when it cools. You're best to use cast aluminium, e.g. transmission casings, engine parts, etc.. They are relatively high-silicon alloys which leads to much less shrinkage. It's easy enough to break those down, throw them in a fire for a bit then hit them with a sledge hammer, they'll basically shatter into small pieces due to hot shortness. If you're serious about casting, I'd recommend spending some time at Alloy Avenue, there is a huge amount of experience with home foundry stuff on tap there.

I don't think you're oxidizing very much aluminum. The interior coating and the exterior paint comprise a significant fraction of the weight of each can. (That amount can probably be calculated fairly well by roasting a couple of cans by hand and weighing the material before and after.) I believe mechanical losses account for most of the unrecovered metal. I should think the dross and dregs could be re-melted and a goodly fraction of the aluminum drained from that mass by use of a steel mesh.

Try a mini muffin pan for a better size

Mini muffin tins.

What is the method to refine the sludge of aluminum can?

Adding some sort of flux to the mix would help borax or maybe some carbonate of some sort

Hey man, just wanted to know if this is still working, really looking forward to getting one!

Can it melt sand ?

So I’ve got a bunch of aluminum muffins but I need powder Do you think I could somehow drill it down into turnings then use a ball mill or just sit for hours with a file

One word FLUX

What’s the name of the effect where you can quickly stick your finger in something hot without being burned?

What's wrong with the can tabs?

You could try melting cast iron

I think aluminum foil would have been a better source of aluminum.

use borax as an flux to bring out more impurities

First

One of these cans has 0.25€ deposit on them in germany. Also they are made from steele and not aluminium due to the alzheimer risk. (only pepsi is still using aluminium)