How to Blue Gun Metal: A Step-by-Step Guide

Blueing, also known as "bluing," is a metal-finishing process used to provide a protective coating to steel, particularly firearm parts, that helps to prevent rust and corrosion while giving the metal an attractive blue-black finish. This method is especially common for firearms, tools, and other metal items. While many people associate the blueing process with firearms, it can be used for a variety of items where steel is exposed to the elements or where a durable, aesthetic finish is desired.

This article will guide you through the steps required to blue gun metal, focusing on the preparation, application, and aftercare of the blueing process. Whether you are restoring a firearm, creating a custom piece, or experimenting with a new project, this guide will help you achieve a professional, durable blueing finish on your steel items.

What is Gun Metal Blueing?

Gun metal blueing is a process that uses chemical reactions to convert the outer layer of steel into a layer of rust-resistant material. This conversion occurs through the interaction of specific chemicals, typically involving a form of oxidizing agent that reacts with the metal's surface to create a uniform blue-black coating.

The blue-black finish obtained through this process is not merely aesthetic; it also serves functional purposes by enhancing corrosion resistance. Blueing is a desirable feature for firearms and other metal items that are regularly exposed to moisture, as it helps prevent rusting. Gun metal blueing can be done through various methods, including hot bluing, cold bluing, and rust bluing, but each method offers different results in terms of appearance, durability, and ease of application.

Types of Blueing Methods

1. Hot Bluing :

   Hot bluing is the most durable method of blueing. It involves immersing the steel parts in a hot, caustic solution, which reacts with the steel to create a protective layer. The process typically takes place in a heated solution, which causes the formation of a black-blue oxide layer that adheres strongly to the metal's surface. Hot bluing is commonly used in industrial and commercial firearm production, as it provides a long-lasting and highly corrosion-resistant finish.

2. Cold Bluing :

   Cold bluing involves applying a cold solution directly to the metal. The solution is typically a mixture of acids and salts that react with the surface of the steel, causing it to darken. While cold bluing is easier to do at home, the finish is generally not as durable or long-lasting as hot bluing. It is most useful for touch-ups, minor repairs, and small-scale applications.

3. Rust Bluing :

   Rust bluing is an older process that involves creating a controlled rusting of the metal, which is then converted into a protective oxide layer. This method requires applying a rusting solution to the steel, allowing it to rust over a period of time, then boiling the parts to remove the rust and convert it into the blue-black finish. Rust bluing is a time-intensive process but is considered by many to be the best for firearms due to its deep, smooth finish and the protection it provides against rust and corrosion.

In this guide, we will focus on the cold blueing method, as it is the most accessible and easiest for individuals working with small parts or firearms. It's also ideal for hobbyists, collectors, and DIY enthusiasts who don't have access to the high-heat and industrial equipment required for hot blueing.

Materials Needed for Blueing Gun Metal

Before starting the blueing process, it's essential to gather the necessary tools and materials. The cold blueing method requires specific chemicals and equipment to achieve a good finish.

1. Cold Bluing Solution

There are various cold bluing solutions available on the market. Some of the most popular brands include Birchwood Casey's "Perma Blue" and Brownells' "Oxpho Blue." These solutions contain a blend of salts and acids that react with the surface of steel to form a blue-black oxide layer. Ensure you select a high-quality cold blueing solution that's compatible with your project.

2. Steel Parts to Blue

Ensure that the metal you're working with is clean, free of rust, and in good condition. Cold bluing works best on steel parts that are properly prepared and free of contamination.

3. Cleaning and Degreasing Solutions

Before applying the cold blueing solution, it's important to thoroughly clean the metal surface to ensure proper adhesion of the blueing solution. A degreaser or cleaning solvent such as acetone or rubbing alcohol can be used to remove oils, dirt, and debris.

4. Fine Steel Wool or Sandpaper

Light abrasives like 0000 steel wool or fine sandpaper are used to smooth the surface of the metal. This process is critical to ensure a consistent and uniform finish when the blueing solution is applied.

5. Protective Gloves and Eye Protection

Cold blueing solutions contain chemicals that can be harmful if they come into contact with the skin or eyes. Always wear rubber gloves and safety goggles when handling the solution to avoid chemical burns or irritation.

6. Towels or Rags

Lint-free towels or rags are needed to wipe the metal parts before and after applying the cold blueing solution. It's important to ensure that no dirt or dust remains on the surface, as this can result in an uneven finish.

7. Neutralizing Solution or Oil

After applying the blueing solution, you'll need a neutralizing solution (often included in blueing kits) to halt the chemical reaction or use a protective oil that helps preserve the finish.

8. Protective Coating (Optional)

To protect your blueing finish further, a thin layer of gun oil or protective coating can be applied after the blueing process. This helps to seal the finish and prevents future corrosion.

Step-by-Step Guide to Blueing Gun Metal

Step 1: Preparation and Cleaning

Preparation is the key to achieving a smooth and uniform blueing finish. If the metal is not properly cleaned and degreased, the cold blueing solution may not adhere correctly, leading to uneven results.

1. Remove All Surface Contaminants

   Using a degreaser or rubbing alcohol, thoroughly clean the steel part. Make sure to remove all oils, dirt, rust, or any other contaminants. The surface must be absolutely clean to ensure proper bonding of the blueing solution.

2. Smooth the Metal Surface

   After cleaning, use fine steel wool or sandpaper to lightly buff the metal surface. This step will help remove any small imperfections, rust spots, or rough areas. The smoother the metal, the better the blueing result will be. For best results, use 0000-grade steel wool for a fine and even finish.

3. Rinse and Dry

   Once the surface has been smoothed, rinse the steel part with warm water to remove any residual cleaning solvent. Dry it thoroughly with a lint-free towel. It's important to work with a completely dry surface to avoid any water spots or interference with the blueing solution.

Step 2: Apply Cold Bluing Solution

Now that your metal part is prepared, it's time to apply the cold blueing solution.

1. Wear Protective Gear

   Always wear gloves and safety glasses when working with cold blueing solutions. These chemicals can be harmful, and it's essential to protect your skin and eyes.

2. Apply the Cold Bluing Solution

   Using a clean, lint-free cloth or cotton swab, gently apply the cold blueing solution to the metal surface. Work in small sections, ensuring that the solution is evenly applied. Do not allow the solution to pool or drip. A light, uniform application is key to a good finish.

3. Allow the Solution to React

   The solution will start to darken the metal almost immediately, typically within a minute. Allow the solution to sit for a few minutes (depending on the product instructions). The exact reaction time may vary depending on the brand of cold bluing solution you're using.

4. Wipe Off Excess Solution

   After the solution has had time to react with the metal, use a clean cloth to gently wipe away any excess blueing solution. This prevents streaks or blotchy areas from forming.

Step 3: Reapply for a Darker Finish

For a deeper, darker finish, you can apply additional coats of the cold blueing solution.

1. Apply Additional Coats

   Apply a second or third coat of the blueing solution, following the same process of application and wiping off excess solution. Each application will gradually darken the metal.

2. Buff Between Coats

   After each coat, lightly buff the metal with 0000 steel wool to smooth out any inconsistencies or unevenness. This step helps ensure that each layer of blueing is even and smooth.

Step 4: Neutralize and Protect the Finish

Once you've achieved the desired blueing depth, it's time to neutralize the chemical reaction.

1. Neutralize the Finish

   Some cold blueing kits come with a neutralizing solution that you apply after blueing. This stops the reaction and seals the finish. If a neutralizer isn't included, you can rinse the steel part with warm water and dry it thoroughly.

2. Apply Protective Oil

   To further protect your newly blued metal part, apply a thin layer of gun oil, motor oil, or a specialized protective coating. This helps prevent the blueing finish from wearing off or being damaged by moisture.

Step 5: Final Touches and Care

Once the blueing process is complete, it's important to continue caring for the metal to maintain the finish.

1. Buff the Metal

   Use a soft cloth to lightly buff the surface of the steel, enhancing the finish and removing any oil residue.

2. Regular Maintenance

   Over time, the blueing finish may wear off in areas with heavy use or exposure to moisture. Regularly oiling your metal parts will help protect the blueing and keep the steel in excellent condition.

3. Storage

   Store your blued items in a dry, cool environment. Avoid exposing them to extreme humidity or moisture for prolonged periods, as this can lead to rust formation.

Conclusion

Blueing gun metal is an excellent way to protect steel parts and enhance their appearance with a rich blue-black finish. While the process requires patience and precision, the results can be highly rewarding, especially when you take the time to follow each step carefully.

By using the cold blueing method, hobbyists and DIY enthusiasts can achieve professional-grade results at home. Proper preparation, the right materials, and attention to detail are essential to ensuring a uniform, durable, and attractive finish.

Whether you're restoring an old firearm, finishing a new tool, or simply experimenting with blueing, this step-by-step guide provides you with the knowledge and techniques necessary to get the job done effectively. With time and practice, you'll be able to perfect your blueing skills and create stunning, rust-resistant metal finishes.

View Product