Blueing is an electrochemical process to protect metal surfaces. It is usually applied to highly tempered and hardened steel such as that used in firearms and swords. The blueing procedure, known as passivation, induces a non-reactive coating of protective oxidation on the surface of the steel to prevent the formation of harmful rust. Two forms of blueing -- hot and cold -- are most commonly used on firearms. Hot blueing is usually performed during manufacture by immersing the steel components in a boiling mixture of potassium nitrate, sodium hydroxide and water. A hot-blued surface is commonly maintained by regular applications of light oil. Off-the-shelf cold-blueing products -- like G96 -- contain selenium dioxide to touch up areas where the manufacturer's hot-blued coating has worn away. Cold blueing restores consistent color to the treated metal, and provides short-term rust protection.
Strip all oil, grease and dirt from the surface with a commercial gun-degreasing-solution. Follow the manufacturer's recommendations.
Sand pitted or rusted surfaces lightly with an emery cloth or steel wool.
Wet a clean cloth patch with G96 gun-bluing solution. Apply G96 evenly to the metal surface.
Flush the blued surface with water, and dry with a clean, soft cloth.
Apply a thin coat of gun oil to maintain the blued finish.
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