Birchwood Casey® offers you the best ways to touch up scratches and worn spots or even completely reblue most guns. It will give a non-streaky, even blue-black finish to steel (except stainless). Both Perma Blue® Liquid Gun Blue and Paste Gun Blue provide great blueing to metal that has already been thoroughly cleaned and is free of rust. Perma Blue® Paste Gun Blue is slower to darken than Liquid Gun Blue, but will build up a denser finish. NOTE: PERMA BLUE® Liquid Gun Blue will not blue stainless steel, aluminum or non-ferrous metals.