that's the first thing I thought of too hank,,too hot. But he's been casting fer 20 years and guided buy the hand of 50 years experiance. I'm sure tween the two they've seen too hot before.
The part of it I cain't figger,, is how rust got "inside" the new pot and they cain't see it? but they think it's there?? ok whatever? Could be rust. Could be a 1 in a million bad pot. I'm thinkin he never scrubed that sucker proir to first melt and has an "oil" contamination.
Tell ya what. you crank that thing till everything is red hot and full,,and leave it there whilst ya skim and skim and skim some more as long as you have courage too. Then turn it off ta cool, afore that lead sets,, you empty that pot. Don't matter what ya do with the lead just empty the pot.
The next day when that pot is cold, you bring it to water with one a them green scrubbie things and soap and scrub it real good, best ya can. Now I'm allowin you got experiance,, and knowin what hot is, what ta get wet and what not too.K? When she's dry the day after that, you start with fresh lead and go slow. Ya need too "temper" the pot, that's as best I can explain. It'll work good now,, if you use that same lead as what got red hot? well then it won't work good.. That's what I know, you do what ya want, I done this already, that's my two bits
luck too ya,