People think casting aluminum is way harder than it actually it. It has a very low melting point, so you can melt it with just about any heat source you can think of. Even a campfire could melt it. Making the casts is also quite cheap, since it's just plaster and sand. The total cost of casting this ring was 5 euros, or about 6 dollars, but I didn't use even close to all of the materials, so in the end, the cost was actually even lower.
Step 1: The Materials
Wood or charcoal for the heat: I used charcoal for my project, but if you have wood laying arround, it will work just as fine. 3 kilos of charcoal cost less than 3 euros.
Aluminum: I got my aluminum from aluminum cans. Some beer or soda cans are made from iron. You can test this out with a magnet. If the magnet sticks to it it most likely isn't aluminum.
Plaster for making the moulds: this costed me 2 euros for one kilo pack, which is more than enough for a small cast like a ring
Sand: We will mix this sand with the plaster in a ratio of 1:1. You could buy some really fine sand somewhere and sift it, but what I did, is I went to the nearest construction site and asked if I can take a shuffle full of sand or two.
Wax: This was the material I used for making the moulds. When the mould was done, I melted the wax and poured it out. I got the wax from melting down a cheap candle.
Step 2: Safety Equipement
This is a very dangerousb project, so use proper protection. There is a small danger that you still have some moisture in your cast, which could cause it to explode and send molten metal flying at you. I wore a leather jacket, a thick leather apron, heavy boots, welding gloves, a face guard and jeans. In 33°C weather. It was worth it tho, since bubbles started forming on the top of the mould and sent tiny droplets of molten aluminum onto my apron.
Step 3: Making the Object for the Mould
You will need to make an object for the plaster to dry arround. You also need to remove this object without damaging the mould itself. This is done by using a material with a low melting point and just heating up the mould untill it flows out.
Start this step by finding a small cylindrical object with a diameter of about 3-4 centimeters. I used a toilet roll tube. Then take your candle and melt it into this cylinder to make a round disc. Then make a hole in the center of this by taking a hot knife and spinning it arround. Do this from both sides. This will give you a more perfectly round hole with a smaller taper.
After you're done with that, take a knife and start making the outter side of the disc smaller. And now you have a wax ring! If you want to give the ring a texture or a patter, you could do that. Take a small ammout of warm wax and roll it between your hands, then weld it to the ring using a hot knife. This will make a channel for the molten metal to flow through.
Step 4: Making the Cast
First you need to prepare your mix. It consists of four parts plaster, four parts sand and three parts water. Get any sort of a container to pour the plaster into it, and then submerge the wax ring into it, making sure a part of the channel is slightly poking out, so we can actually pour the metal in. Leave it over night so there is less of a chance of any moisture still inside it. Then take the cast and put it upside down in the oven at arround 150°C. This will melt the wax and let it flow out, making way for the aluminum.
Step 5: Melting the Aluminum
You will first need to find something to use as a crucible. You can use anything that is made from only metal, like a frying pan with it's handle removed. I used an old coffee pot. Sometimes handles are rivveted on these things with aluminum and other low melting point metals, so be careful of what you use. You don't want to grab it by the handle with pliers and have it drop on the ground, splashing you with molten metal.
Find a place to build a fire. You can use wood or charcoal, or simply blast the aluminum with a propane torch untill it melts. Best places to smelt aluminum are small confined spaces made from a material that doesnt melt, such as an old wood burning stove. I simply used fireplace. If you used wood for this project, you need to wait for your fire to burn down to the embers, which burn at a much higher heat. You could place it on the fire itself and it would probably be hot enough tho. Place your crucible and aluminum onto the embers and start fanning it with a big piece of cardboard. Now it's only a matter of time before it melts.
Step 6: Pouring the Molten Metal
This is where the safety gear is required. You could drop the crucible splashing and burning yourself, or your mould could crack or even explode if you didn't dry it for long enough.
When you take the crucible off the heat, you have about 2 minutes before your aluminum solidifies again, depending on the heat of your fire, so you don't need to rush too much.
Step 7: Sanding
Even if you did everything right, your ring will probably be slightly crooked and full of bumps and holes from the casting. If you have a drill or a powered screwdriver at home, you can do what I did. I attatched he ring to a stick that I thinned down torwards the end, then just spin up the screwdriver and hold sandpaper to it. This also gave it a brushed metal look, so I decided to not use and finer grits since I quite liked that look, but you could definatly keep going and even polish it at the end.