The Step By Step Guide On How To Blue a Gun

Bluing is a method many gun users use to treat the metal of their gun so that it has a protective shell around it. This treatment can also be called black oxidizing. The treatment turns the red iron oxide into black iron oxide. It’s the blue-black color that gives the treatment its name of bluing.

There are 3 techniques on how to blue a gun; hot bluing, cold bluing, and rust / fume bluing.

Here are step by step guides on how to blue a gun for each technique

How to blue a gun using hot bluing technique:

  1. Polish – You need to remove all red oxides and surface dust, as well as any scratches on the steel. Use either sandpaper or steel wool.
  2. Rig the parts you will dip into cleaning and bluing solution – Expect whichever bluing solution you use to be extremely caustic. In some cases, even the chemicals used in the cleaning solution can also be caustic. Obviously you will need some rubber gloves, but by rigging up the parts to be dipped, you can ensure you can get them out of the bluing bath safely. Use some soft wire and thread it through the barrel (ensure it is longer than the actual barrel). Then bend both ends into little hooks which you can grasp without the need to actually touch the barrel. If you have smaller parts that need bluing, hold them in a stainless steel bucket.
  3. Dip the parts to be blued into cleaning solution – There are different cleaners you can choose from. Sodium triphosphate is used in many commercial cleaning solutions. Or you could use naphtha and then wash the steel with mild dishwashing liquid. Also, some people prefer using a specialist oil and then following by nail polish remover (acetone) or denatured alcohol. Whatever solution you use, you need to immerse the steel parts for around 15 minutes. This ensures all grease, dirt and oil is removed, as these can hinder the bluing process.
  4. Wash off all traces of the cleaning solution – rinse for at least 3 minutes to ensure all traces are gone.
  5. Stir through the bluing solution and then heat – Bluing solution is a mixture of sodium hydroxide and potassium nitrate. It can have clumps of bluing salt at the bottom or on the surface. Stir thoroughly to get an even solution. Then, it needs to be heated to around 275-310 degrees Fahrenheit (135-155 degrees Celsius). Stainless steel gun parts are blued using a mixture of chromates and nitrates, and this also needs to be heated to the same temperatures.
  6. Dip the steel into the bluing solution – Immerse the complete barrel and try to dip at an angle, as this allows any air bubbles to escape. If you are bluing smaller gun parts, stir the metal basket containing the parts so that the bluing solution completely covers them.
  7. Leave the metal in the bluing solution for 15-30 minutes – You can check to see if they’re done by looking at the color. Remove from solution only once you can see that the metal is the shade of blue-black that you want.
  8. Rinse off the bluing solution – Use cold water, as it helps to wash away the bluing salts better than warm or hot water.
  9. Put your gun parts into boiling water – Immerse the parts completely. This is to ensure all bluing solution is boiled off. You need to immerse your gun parts for 5-10 minutes at least, with some complex parts needing around 30 minutes.
  10. Apply a chemical to soldered parts – You may notice some parts of your gun that have not gone a blue-black shade. These are soldered parts, and there is a chemical you can use to paint over these parts so it matches the blue-black of the rest of your gun. You can use cotton wool for this.
  11. Immerse your gun parts in a water-displacing oil bath – Allow your gun parts to sit in this oil bath for 45-60 minutes, until they cool. This protects the parts from sweat, rust and body oil.

How to blue a gun using cold bluing technique:

  1. As with hot bluing, polish the metal – Use sandpaper or steel wool.
  2. Decide whether you are bluing your entire gun or just touching up existing bluing – If bluing whole gun, immerse all metal into a cleaning solution, as with the hot bluing technique. However, if you are touching up existing bluing, you can simply apply some cleaning oil where you want to remove old bluing. Be careful, as this cleaning oil does dissolve bluing, so ensure you only apply it to where you want to remove bluing. You may create scars which need to be polished out. Use nail polish remover (acetone) to remove the cleaning oil.
  3. Heat the metal gun parts – Yes, we know it’s called the cold bluing technique, but heating the metal gently, before you apply the bluing solution, allows it to absorb the solution better, creating a more polished finish. You can use a heat gun, blow dryer, an oven set to a low temperature, or even just leave your gun out in the sun for a few hours.
  4. Apply the bluing solution to your gun parts – Use a clean applicator and apply the solution as evenly as you can. You don’t want a mottled appearance, so you are looking to do sections of about 3 inches (7.5 cm) at a time. Slowly does it, and then smooth out any scars with steel wool. You can use new toothbrushes or even old cotton t-shirts to blue large areas, whilst smaller parts can be blued using cotton balls or toothpicks. A good tip for when you have limited bluing solution is to put it into a spray bottle and spray it onto gun parts with a plastic tray behind it. The tray will catch the excess solution and you can simply pour it back into the spray bottle and spray again.
  5. Apply the bluing solution several times – Check the color and only stop once you are satisfied with the blue-black color. For each layer, use a fresh applicator, and use fresh steel wool to smooth out each layer before you move on to do another layer. You will need around 7 layers altogether.
  6. Sand spots on the metal that appear light – You may get some stubborn spots that won’t darken. Simply sand the spots with sandpaper and apply the bluing solution again. Try to only sand the light spots and not accidentally sand parts that have got to the desired blue-black color.
  7. Apply layers of gun oil – Apply a layer of this oil every 2-4 hours. Before each new layer, wipe off the previous layer using cotton wool. This is to wash of the bluing solution as, with the cold bluing technique, you cannot wash off with water (as with the hot bluing technique). This gun oil is a different oil to the cleaning oil. Don’t get these mixed up as the cleaning oil will actually start taking off the bluing and undoing all your hard work!

MidwayUSA provides a video on how to blue a gun using the Belgium Blue:


How to blue a gun using rust / fume bluing technique:

  1. As with the other two techniques, polish all the gun parts that you want to blue – Remove all scars, pits and rust using sandpaper or steel wool.
  2. If removing the factory finish on a new gun, use either white vinegar (acetic acid) or phosphoric acid-based rust remover.
  3. Use a cleaning solution to get rid of grease, dirt and oil from the gun parts – You can use any of the solutions described above in the hot bluing technique. Removing dirt and oil makes the bluing adhere to the gun parts much more effectively.
  4. Use acid solution to coat all the metal parts – The acid solution is made up of nitric and hydrochloric acid. The idea is that it actually rusts the metal, but it rusts evenly. You could also simply place the gun parts into an acid bath and leave it in a cabinet for around 12 hours. This is called fume bluing, and the acid will evaporate from the bath and condense around the metal.
  5. Wash the gun parts in distilled water that has been boiled – Ensure you immerse your gun parts fully. This removes the acid solution and halts the rusting process.
  6. Remove the red oxide rust – The desired blue-black oxide is underneath, so scrub off the red oxide using a carding brush or wheel with soft and thin wire brushes.
  7. Repeat the application of acid, washing with boiled water and scrubbing until you get the level of bluing you want.
  8. Coat the blued gun parts with gun oil – Let the parts sit overnight to allow the oil to really sink in. This oil protects the gun metal from sweat, dirt, wear and body oil.

MidwayUSA provides a video showing how to blue a gun using the rust technique:


There is no ‘preferred’ technique on how to blue a gun. Ask each gun user who has blued their gun, and they will each have their own preference. You will only know which technique you prefer after trying all three. But whichever technique you use, bluing your gun is worthwhile process when wanting to protect your gun from wear and tear in the long run.

We hope you found this article on how to blue a gun useful. If you have some thoughts on the subject, please feel free to leave a comment in the comments section.