Step 4: Melting Aluminium
You're going to want to fire it up and put in your crucible.
I'd wait until the bottom of the crucible is red hot. (just a personal preference.)
Start out with small pieces of aluminum. (I had "pipes" from an old wind chime.) You could use cans but they tend to have a lot of slag. I'd wait until you have a nice quantity of aluminum before using cans.
You'll probably have a rough start so go slow. After you get a good quantity of aluminum it will be able to maintain a melting temperature and you can melt down large pieces in seconds. I have found an old knock off of a razor scooter in th back of my garage that has worn out it's usefulness. I found a new use for it's aluminum.
I have found covering the crucible with the top half of the empty propane tank helps keep the heat in and keeps things moving along nicely.
I had a troublesome piece of scooter that didn't want to release it's steel screw so I dunked it in the pool of molten madness and that half didn't come back. A mallet made short work of the obstructing piece of metal and allowed us to make a deposit in our crucible.
After you either fill up your crucible or run out of aluminum, you need to scrape off the slag. The slag will be floating on the top and will look a little different than the metal underneath.
We used a scrap piece of metal to scrape off the slag. We used the same scrap to make a hook to pick up the crucible and another piece to fit in the holes on the bottom of the crucible so you can easily pour it. You could use a small screw driver for this.
Make sure you have something to pour the aluminum into. I am just going to save them for later so I'm pouring them into one of those "mini muffin" tins just because they're small and fit in the crucible. You could just use an impression in wet sand or something. Muffin tins are faster. But don't expect to use them for muffins again.
Pour gently into the mold of your choice. IT IS HOT! WEAR PROTECTIVE EQUIPMENT!
Because I'm impatient, I wait until the aluminum in the tins are solid then throw them into a can of water. The water may boil violently after a short delay. It is a sight to behold but dangerous.
You now have aluminum ingots.