I have been melting COWW for a while now and sorting wears me out. So I smelt as low of a temp as I can which takes a long time as opposed to my known clean stuff that I pour the heat to and get knocked out. So to be cautious I picked up a thermometer and the COWW according to the thermo is melting at 500 deg. I skimm off the non lead and take it on up to almost 600 then ladle it out into ingots. Don't get me wrong at 500 it is barely fluid. At 600 it ladles and pours easily.
Always possible the new thermo is **** as well.