The longest lasting finish, but slower to darken than the liquid blues. Easy-to-use, Birchwood Perma Blue Paste Gun Blue reacts slowly with the metal but builds up a denser finish that will outlast the liquid blues. Birchwood Perma Blue Paste Gun Blue is excellent for touch-up or complete reblueing. Metal must be clean and free of rust and sealed with BARRICADE Rust Protection to enhance and protect the finish. A dark blue color may require three or more applications of Perma Blue Paste but each coat takes only 30 to 60 seconds to work. Complete instructions on each tube. Apply with cotton swab.