I've been saving up my lead gathered from the scrap yard and processed it this week. As usual, most of it was clip on wheel weights. But I also had some plumbing joint lead (lead ocum joints) and some flashing lead. When I melted and fluxed the lead joint I got a rainbow of blue gold and some red across the surface. Ditto with the flashing lead. I've read what this is somewhere but can't find the location.
All the wheel weight both soft and clip on along with the diver weights were what I usually see when smelted. And I have had lead joint and flashing in the past that didn't exhibit the rainbow.
Can anyone explain what is causing the rainbow?