Scrap aluminum from foil or drinks cans can be melted down using a propane blowtorch. The metal has a melting point of 1,200 degrees Fahrenheit (660 degrees Celsius), but ordinary propane blowtorches produce flames twice that temperature. Impurities such as paint form a scum called dross which is skimmed off. The molten aluminum can be cooled in steel molds and stored as ingots for later use. The entire process is performed outside on the ground for ventilation and to avoid scorching surfaces.
Fill a large glass bowl with ordinary sand. Sand is an insulator and will protect the bowl and ground from the torch heat.
Place the bowl on a flat piece of ground outside. The bowl should be stable, and the area should be well ventilated because melting aluminum can give off toxic fumes as its impurities burn.
Push a steel cup into the sand. The edge of the cup should still be visible, but it should be almost entirely submerged in the sand and stably supported.
Compact your scrap aluminum pieces as small as possible. Squash foil into a ball and crush cans. This helps the metal melt more easily.
Put one piece of aluminum scrap inside the steel cup. The cup acts as a "crucible" when you melt the aluminum with the blowtorch.
Heat the piece of scrap with the blowtorch until it melts. As the first piece melts, add more pieces of scrap metal. The more molten aluminum there is in the crucible, the faster the new pieces of scrap will melt.
Skim any scum off the top of the aluminum with a steel ladle. Leave this to cool before discarding.
Use long-handled pliers to pick up the crucible after all the scrap is melted. Pour the aluminum into steel muffin tins. When cool, these ingots can be stored for later use.
Do this in a controlled environment where you will not be interrupted, molten aluminum is very dangerous. Never handle any of the equipment after use until you are certain it has cooled sufficiently.
When using a blowtorch keep a bucket of cold water at hand in case you need to dowse any unexpected flames.