I picked up some casting sand from a local aluminum foundry this weekend and spent Sunday putting together a small test casting. Rather than using aluminum, which is a challenge to melt in a soup can, I used a few rolls of pennies as a source for some zinc.
It took a few tries to get the cope rammed up properly. I had trouble getting the sand inside the pattern rammed hard enough and strongly connected to the rest of the sand in the cope. It did work out nicely though. I took some pictures of the casting process and the resulting object.