You can get some interesting coloring and patterns with this method. First get a clean, bare steel surface by sanding or other methods. Wet metal with water and sprinkle with salt, I prefer the patterns from coarse salt or rock salt. Heat with a propane torch until you see the colors you want and quench in water. Rinse off all the salt, dry and apply oil or clear finish immediatly before it rusts. The sample in the photo was done with fine grain salt, I didn't have any rock salt on hand.