My husband fells trees, chainsaws/axe's wood by the chord; he works on semi-tires & many other DIRTY jobs & after he is done for the day, he hangs his pants and most of the dirt falls off over night & he occasionally asks me if I laundered them!  The teflon coating really works well!  He got pitch on several spots & I was able to remove it with WD40 even though the sap had been marinating in the fabric for several days on the seat of the pants & knees.  I am really impressed with these pants as they are the first to provide my hubby with a challenge in destroying them!