all of the skulls that i have done(boiled) all told take several hours. i start with a large stock pot and half a bottle of lemon juice(helps eat away bit's of flesh and takes away from the stink) every 1/2 hour or so i will pull the skull and take a small sharp knife and scrape at the skull. keep a eye on the lower jaw bone(if you plan on saving that)because that along with the nose plate are the weakest part of the skull.