A quick and dirty double boiler for melting wax. Get a PET softdrink bottle and cut it like this:
(photo to come)
Put the wax in the cavity, and float in a pot of boiling water. Takes a while to melt the wax, and the bottle gets a bit deformed, but works pretty well. Not sure I’d use this for food, as the PET bottle might leech chemicals on heating, but perfectly fine for candlemaking wax melting.