So when I melt down my WW, I flux, stir, and skim the clips off obviously. I periodically flux and stir like I'm supposed to, but if I go for an extended session, "dirt" for lack of a better term turns up on the surface of of the alloy and won't flux or mix back in.
I just got back from putting my pot up after letting it cool down and it was on top and just dumped out.. It's the consistency of mildly sandy dirt and has flakes of yellow in it.
What is it and what should I do with it?