Hi- got some lead gaskets from sewer pipes in an old school tear down - I have been using it for over a year with no problem. Yesterday I was melting some to clean it up, and I kept getting this yellow gold flakey stuff ( a lot of) I kept skimming it off and fluxing but it kept on coming. I worked at it about an hour with no end in sight. So I poured it out and let it cool.I noticed after it cooled it had a blue color to the lead only on the side that was poured out last. Any idea as to what it is and how to clean the lead.Thanks