Here's a variety of ingot molds I used to re-claim range lead. The big muffin tin is steel, but NOT tin plated steel. That's where the problem arrises, the tin plated steel tins solder the lead right to the steel. Hard to see at the bottom of the pic is 2 teflon coated aluminum muffin tins. They worked great, but I suspect they may have fumed when we first filled them with hot lead. Nobody died----hack/caff/gag!
That was 2 years ago, so it looks like we survived
The mold at the lower right corner is one my buddy made from channel iron scrap. It makes a 5 pound ingot that still fits into my lee 20 pounder.
I wish he had made 4 of them!