If it were me, I don't know if the lead pot would be questionable for casting afterwards. The melted stump stuff can be used over and over again, so it could be a good idea to dedicate one pot for it and just leave it in there.
I know many folks do it, but I'd rather use gas burners around bluing type salts than electric wiring and elements. It may just be me, but the life seems to be shortened. I checked to make sure it's still there, but Brownells nitre blue instruction pdf seems to be a really good guide even though it's not their product.
