Heavy Weight Muslin is used to cover soft or hard flats or for drops. Its greater "body" means that it will typically have a longer life than lighter weight muslin. When estimating yardage for covering flats, allow at least 6" of extra fabric on all sides. Trim the excess after sizing the flat. Flame-retardant Muslin is used for unpainted drops such as cycs or surrounds. It can also be painted, but heavy paint treatments will require special techniques to prevent recrystallizing of the FR chemical salts.