Smelting Aluminum

Got together at my friend/boss Don's house to smelt some aluminum. This was a pretty rudimentary setup, with a bucket lined with special heat resistant cement and a hole in the bottom to blow air under the charcoal briquettes. We had an ingot mold and a plaster casting of a 3d printed octopus (because why not?). We did a couple of tries with the plaster cast and were hoping at first that we could leave the printed piece in the mold and let the molten aluminum get rid of it for us like with the lost wax casting method, which was partially successful with the legs but the body of the octopus had nowhere to go and the white plastic ended up a pretty nasty mix of yellow-brown/black with bubbles. We also found that we got a better casting with the molds pre-heated in an electric kiln, which gives the molten aluminum more time to fill the cast before cooling. The major differences we noticed in the ingots were better defined angles on the corners and less dimples on the surface of the ingots. This setup was far from ideal however, as we kept getting bits of ash and charcoal into the aluminum and there was a lot of waste product. After doing some cost analysis with BTU output data found on the internet we came to the conclusion that a propane burner would give the best results with the lowest cost, and would provide better heating and less contamination in the aluminum. We tested melting the aluminum with a handheld propane blowtorch and were able to melt a small bit of aluminum, but a bigger burner would be a lot more effective.