I’m starting to wonder if some modern clip-on wheel weights have a small percentage of zinc in them. I schmelt 10# batches and sometimes there just a little bit of oatmeal in there, even when I used tin snips to check every wheel weight. My habit now is to flux with enough Root Kill to clean out about 0.1% of zinc (if it’s there). Sometimes I have to do a second Root Kill flux to clear the oatmeal. Maybe it’s some other impurity, not sure.