I don't know about glass, but any junk in molten metal just burns up and the ashes can be skimmed off the top. It's not really the metal I'm talking about, it's

I don't know about glass, but any junk in molten metal just burns up and the ashes can be skimmed off the top. It's not really the metal I'm talking about, it's the plastic and paper which are pointless to even have in the system.