I used to melt old tire balancing weights into diving belt weights in a cast iron dutch oven on a Coleman propane stove outside. I reckon you are looking for a little finer finished product, but I never had any problems, and never scooped off any crap off'n the top of the mess. I had a small smelting pot, but it wasn't big enough to do the diving weights it was made for making bullets and fishing jigs, I think.