Been melting lead for years into ingots than casting, into round ball. For the last year or so, I have been meeting to cast bullets. Never have I ran across this. I was able to pick up some 290lbs of leas sheet from what I was told, came from an xray room walls. I was melting it and the top of the lead in my cast iron pot was a rainbow, green orange red color, my temp was at 720ish. I am assuming this is from the lead being pure lead? I have melted and made ingots at a slight higher temp, so I don't think it was too hot. Any help would be greatly appreciated, and thank you in advance.