I just can't help buy feel that we might not be the best source of information for the OP. Most of us are scrappers and not refiners. There's always been a generally agreed upon prohibition of discussions that have to deal with refining because of the dangers involved.



If we did set up a furnace to purify our metals into ingots ... our scrapyard probably wouldn't accept them.

What he's asking about is generally outside the range of our direct experience unless we've worked in an industrial foundry before ?