How To Blue A Gun

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If you are interested in bluing or putting blue finish on your gun, you need to know the ways to do it, what will blue and what will not blue. The time to blue a gun ranges from a few minutes work to hours.

Gun bluing puts a protective finish on steel. Think of it as a thin protective shell. This provides corrosion and rust resistance. It is not complete protection as longtime gun owners know. Blued steel can still rust or corrode, just not as fast as naked metal. You need a good gun oil to protect the metal.

The coating is actually a form of controlled rusting done with a bluing solution. The rust bluing solution varies with the kind of work you are doing. Bluing can be done on brass, steel, cast iron and stainless steel parts.

I am Ben Baker, a lifelong hunter. I've worked on guns most of my life and recently opened a gunsmith shop to work on guns for other people.


Before you begin bluing steel, you must prepare the metal. This is critical. Depending on the parts you are bluing, you have to take the gun apart. The chemicals and processes will ruin wood and some polymers. 

If you are rebluing the end of gun barrels, you can leave the gun intact. If you are rebluing the trigger on a handgun, you have to remove the trigger for a hot blue. If you are just retouching with, you can get away with leaving the trigger on if you are very careful.

The gun metal must be as clean as possible. A typical cleaning solution is not enough. All rust, dirt, gun oil, and existing bluing have to be removed from the gun metal. If you are doing a complete reblue, then you need to strip all the current finish off. Steel wool is a great help here. 

bluing steel

Steel Cleaning Wool

Once the metal is stripped, you cannot touch it with your bare hands. Oils from your skin will get on the metal and this will affect the bluing. Use clean pliers, tongs or a metal pole to handle the pieces you are bluing.

If you are only doing a gun barrel or other firearm components, just strip those parts. The same pot can do several gun barrels and small metal parts at once.

Naval Jelly removes rust and bluing. It also removes gun oil and paint. Naval Jelly is a concentrated acid solution of phosphoric acid (the same stuff in many soft drinks) and sulfuric acid and some other compounds. This acid solution will cause severe chemical burns. Heavy rubber gloves are recommended. Scrubbing the parts with steel wool ensures all rust and blue is removed.

bluing solutions

If you use Naval Jelly to clean your gun parts, then handle the parts with clean pliers or tongs. Scrub the metal surfaces with a wire brush or steel wool to remove all the rust, pain or oils. When you are done with this, you also need to wash any extra Naval Jelly off the metal. Brake cleaner is an excellent choice to thoroughly clean the parts. 

You can use other gun solvents, provided they will evaporate and do not contain lubricating oils. A final wipe with denatured alcohol is fine. You can use a heat gun to speed the drying process. Toss the steel wool when you are done.

If you are using "white" metal or metal that was never blued, denatured alcohol will clean it. A hairdryer will speed the evaporation.

Things You Will Need

Here is the shortlist of the things you will need. Each subsection goes into greater detail.

• A pot big enough to submerge the parts underwater for several of the techniques described below. This needs to be heavy duty is you plan to do many guns. The chemicals are pretty harsh.

• A rust remover.

• A caustic salt mixture, which is the bluing material.

• Coldwater.

• A heating source.

• Tools to handle cleaned gun parts.

• Patience.

Steps For Bluing A Gun

The steps to putting this kind of finish on a firearm vary with the technique used. Bluing is actually a black iron oxide that becomes a gun's finish. Bluing is done mainly through two different processes, cold bluing and hot bluing. 

how to blue a gun

The other ways are niter bluing, charcoal bluing and heat bluing. Another technique called rust bluing is rarely done because it takes so long. The bluing solution depends on the process. All work should be done in a well-ventilated space. The bluing solution used in most bluing processes are dangerous.

Cold Bluing

The cold bluing process is done at room temperature using the chemical selenium dioxide as the bluing solution. While you can coat an entire gun with this bluing process, most people use this only for touching up spots on gun parts that need to be recoated. Probably the most popular kit is Birchwood Casey super blue. Other companies also sell cold blue solutions.

The chief objection to cold bluing is the coating is hard to apply evenly. If you do not care about this, cold bluing is easier and cheaper than hot bluing. Cold bluing is not as durable as hot bluing. It will wear off sooner. A cold kit has everything you need for the actual bluing, but not the cleaning. While cotton swabs are supplied, you may want to have a cotton ball or two on standby.

Birchwood Casey walks you through this gun bluing process in this video.

Hot Blue

The hot bluing process is done with bluing chemicals in boiling water. The usual chemicals are potassium nitrate, also known as saltpeter, and sodium hydroxide, also known as lye or caustic soda. If you want to try hot bluing, you should order these materials from a dealer that sells them specifically for metal bluing.

Hot bluing is more durable than cold bluing. It is also more expensive than cold bluing. You will need a heat source which is much more than a heat gun, water and a tank to submerge the metal in for the bluing and a tank to quench it. The hot bluing method also creates the traditional caustic black coating seen on blue gun barrels and other parts.

Karl Anderson, a blacksmith, blues his knives. The process is exactly the same for gun parts. He explains the process in this video.

Nitre Bluing

Nitre bluing also uses a chemical process to put blue on a gun with sodium and potassium nitrates. This process creates a marbling effect of blue hues on gun parts. It is beautiful and often seen on custom and high-dollar firearms. This should only be done on non-moving parts as the finish is less durable than most other bluing. 

You can do this kind of bluing at home. You will need some dedicated pots for the process. Nitre bluing also requires temperatures of around 600 degrees Fahrenheit, which ie beyond the reach of a heat gun except for smaller parts.

Walter Sorrells, another knife maker, has a short video showing how to nitre blue.

Charcoal Bluing

Charcoal bluing is the second oldest technique for bluing metal. Unlike the methods above, it does not use chemicals. It does use heat. It is not durable and over time will fade to the antique patina seen on antique firearms.

The short version is the metal is covered in hot coals for a bit, pulled out, and rubbed down with rottenstone. This process is repeated until the desired finish is achieved. This is definitely a project that has to be done outside because of the charcoal.

Heat Bluing

Heat bluing is the oldest method of bluing metal. It is exactly what it sounds like, using heat to change the color of the metal. You can do it with a common butane torch. It is not very durable. Heating metal also changes the structure of the metal. In the case of heat bluing, it makes the metal weaker. Heat bluing should never be used on pressure-bearing parts like a barrel or cylinder. Heat bluing can create a rainbow effect in the metal.

Stainless Steel

Stainless steel can be blued, but the process is even more involved than hot bluing. The properties of the metal mean it does not react to the bluing salts the same way other iron-based metals will. If you really need this done, find a qualified gunsmith to do the work.

Other Parts

Bluing will not work on aluminum, polymer, or most other parts not made from steel. Aluminum has to be painted or powder-coated. Polymer either has to be painted or the dyes mixed into the polymer during casting. 

Plastic has to be painted or the dyes mixed in while the part is cast. An exception to this is brass. If you have brass parts on your gun, you can cold blue them. Brass is most common on black powder firearms.

Final Thoughts

Bluing, or rust bluing, is often something people prefer to have an expert do. If you are interested in investing some time working with scrap metal or a gun barrel that is inexpensive, you can do it. A normal gun cleaning solution will not harm the properly blued metal. Once you get the process down, you can blue a gun of any kind.

A competent gunsmith or someone who evaluates guns can tell the difference between a professional job and an amateur job. In general, the pro's work will not affect the value of a gun. A poorly done job will lower the value of the firearm. If you just need to recoat that dove or duck gun, give it a try. If you want a new finish on a valuable gun, an antique, or heirloom, check with a professional.

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