Heat treat furnace

[Roadracer_Al]

Not that I'm a heat-treat expert, but on the few knives I've done with stainless foil, I have put a piece of newspaper about the same size as the blade into the foil. IMHO, you probably can't put too much in as it will simply consume the oxygen until it's gone then just char. I doubt that you can significantly add carbon to the steel by using a slip of newspaper, but that you could with a charcoal dust pack.