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Ribstone Gunsmithing

Rust Bluing

BSS Blue BSS Blue
Top gun is reblued, bottom gun is a factory original finish.

What is Rust Bluing?

There are several methods for preserving metal that are referred to as bluing, browning or blacking. Most likely you have heard the terms "Cold Blue" and "Hot Blue".

Cold bluing is a chemical method of darkening the steel. Even the best cold bluing chemicals don't leave a lasting finish, and are often uneven in how they darken the steel. Cold Blue is a great way to touch up a scratch, but it doesn't leave lasting protection, and can be hit and miss in how well it covers.

Hot bluing is a method of darkening steel in hot caustic salts. It requires several different "baths" during the process. Hot blue results are very dependent on the polish level on the steel before being blued, it hides nothing, however it can give a fantastic high gloss finish if the preparatory work is done correctly. The time involvement in hot bluing is mostly in the polishing. The actual bluing is a relatively quick process. However it takes multiple tanks all running at high heat and many giving off some toxic chemicals, necessitating a large quantity of work to be blued at once in order to be cost effective. This is why it is a great method in factories, and the method used by factories on most new modern firearms. Factories can't take 3 days to blue a firearm.

Rust bluing is a method of converting red oxide (rust) to black oxide. It is probably the oldest method of protecting gun steel, and the slowest method. Rust blue is a more matte finish than a highly polished hot blue is, however; it is a very even and deep rich matte black. Rust bluing actually converts the outer layers of the steel to a protective layer of black oxide and is generally thought to offer the best protection of any of the bluing processes. The process involves very lightly but evenly rusting the surfaces to be blued, then using hot water/steam to convert the red oxide into black oxide. The black oxide is very stable and aids in preventing the formation of red oxide. The difficulty is that it takes several applications of this process to get the rich deep black color, and maximum protection.

Benefits of Rust Bluing

  • Deep Black Matte Finish.
  • Best Rust protection of any bluing process.
  • Doesn't require excessive polishing.
  • Hides minor pitting much better then a Hot or Cold blue can, so an excellent choice for a firearm that has had a few miles on it.
  • Can be done efficiently in smaller batch sizes than Hot bluing.
  • Can be used on double barrel guns. Rust bluing, while still a hot process runs much cooler then Hot bluing, and won't melt solder. Hot bluing double barrels runs the risk of barrels and ribs coming unsoldered.

Disadvantages of Rust Bluing

  • Most labour intensive and longest time frame, it takes 2-4 days to complete most bluing jobs.
  • The process of rusting roughens the surface, anything above a 320-400 grit polish will be undone by the Rust bluing process, therefore; you cannot get a "High Gloss" finish.

I want my firearm Rust Blued, what should I do?

If your firearm is already rusty, don't "help" by wire wheeling off the rust. If the rust is too thick we may need to remove some of it, but the first step will be to convert as much of the existing rust as possible to black oxide. A good coat of your favorite oil will help slow the current rusting, but don't procrasinate and let the rust do any more pitting and damage than it may have already. Contact us and start the restoration process as soon as possible.

Examples of Work

BSS Blue BSS Blue
An example of some badly rusted barrels that were cut in half for a before and after sample.