The water temperature for scalding has to be between 55 and 60 degrees C, not more or less. Too hot and it cooks the pig, too low and it doesn't work. I think I was told de-hairing had to be done within seconds/minutes of slaughter, otherwise the hairs set in the skin. The problem is often caused by black hairs growing at a very shallow angle in the skin, so a lot of the visible hair is just below the skin surface and cannot be scraped out as can a hair growing at right angles. Either way, black hairs visible on the back fat cook out completely on roasting and end up colourless, and you should end up with crackling that looks exactly the same as back fat that was hairless to begin with. Tamsadedle