Hot Caustic Bluing
Firearm refinishing is one of the most rewarding phases of the Gunsmithing work. Few Gunsmithing operations are as gratifying as seeing a rusted and badly abused firearm turned into a beautiful, rich, blue-black finished firearm. For those unfamiliar with the firearm bluing operation, the process is like magic. It turns a worn firearm into one that looks brand new. Here at Bose’s Guns we know that the process is not an act of magic. But rather, it is accomplished by a masterful job of brightly polishing all the surfaces, keeping the corners sharp, and not funneling the screw holes. We make certain the firearm is thoroughly degreased and rinsed before being put into the bluing solution the results are rewarding a perfect blue-black finish on the steel that will last for years. We take pride in ensuring your firearm is treated with care and in a professional manner.
Hot caustic bluing with Oxynate #7 has been around for over 60 years and has been used by thousands of gunsmiths, which is why we use it. It is a “tried and true” process that works beautifully and will give the firearm a deep blue-black finish that will hold up for years.
The process for Bluing is simply a control over the rusting process. Once the rusting process is stopped with Bluing, it is extremely hard for rust to start again.
Start a rusting process and when the color gets right stop the rusting process, simple right?
Not so simple. Bose’s Guns uses an extensive process to give our customers the best and most durable finish on their firearms. The bluing process is the same for a $100.00 gun to a $10,000 gun. The only difference is the prep time.
Let’s Look at the Process
Remember this is done only after the firearm is completely disassembled and all of the metalwork has been done which is described on other pages in the different finishes Matte/Standard, Deluxe, and Master.
Overview of the Hot Caustic Bluing Process performed at Bose’s Guns:
1. Complete Disassembly and Inspection of Parts
This is one of the most important portions of the operation in regard to the function of the firearm. All parts are inspected for wear or damage and the customer is advised on what it will take to put the firearm back to 100%.
2. Degrease and Chemically Remove Blue and Rust From All Metal Surfaces That Will Be Blued
This is a key process in stopping and removing rust in all areas. Polishing will not reach into the internal parts of the firearm, so this is where we chemically remove the blue from the parts. Leaving the part true to its original dimensions with the blue and rust removed.
3. Metal Finish
At this point the firearm is ready for the desired finish which is described on other pages on the different finishes Matte/Standard, Deluxe, and Master.
4. Chemically Cleaning the Metal
Chemically cleaning the metal is performed by using a slightly alkaline detergent cleaner that is formulated particularly for cleaning guns prior to bluing. It removes all grease, dirt, and crud and puts that material into suspension. It is strong enough to do the job right yet it is totally safe to use and harmless to the steel and of course us. At the end of this phase, all parts are considered surgically clean. Ensuring the cleanliness of the parts is crucial to ensuring a beautiful finish.
Fact: 50% of the problem with bluing can be traced back to something done wrong in the cleaning process.
5. Flowing Water Rinse Tank
Strangely enough, clean, clear water that is safe for drinking is not necessarily safe for blue parts. At Bose’s Guns, we use charcoal filters to make ensure we have zero contaminates in the water. Contaminated water will offset the chemical balance of the bluing solution. We us this tank to primarily remove any traces of the cleaning solution.
6. Hot Blue Tank – Oxynate No. 7
For over 60 years Oxynate No.7 is the most popular of bluing salts. This bluing salt meets Mil-Spec C13924BAM1, Class 1, Grade A. Simply the best gun blue modern science and research can produce. Understanding the principles of the bluing tank is known as “Super-saturation”.
What is Super-Saturation?
Here is a good example of this process: Take a cup of water, pour it into a pan and place it on a stove without heat. Now start adding table salt and stir. Notice you can only dissolve so much table salt in the water. If you turn on the heat, you will discover that as the water heats up, more and more salt can be dissolved. As more salt dissolves in the water, the boiling point of the salt/water solution goes up beyond the boiling point of plain water, which is 212 degrees Fahrenheit. The hotter the solution the more salt that can dissolve, and the higher the temperature at which it boils.
Oxygenate No. 7 works in the same manner. In order to get enough bluing salt into the water solution, the water has to be heated to allow a higher concentrate bluing salts to dissolve into the water, which is enough to turn steel Blue-Black in color instead of some other color.
When the level of Super-saturation is such that the boiling point of the bluing salts/water solution is 292 degrees Fahrenheit, the solution has the proper balance of bluing salts and water. The temperature is controlled by the amount of bluing solution/water mix. Add too much bluing salt and the temperature goes up. Add too much water the temperature goes down. This is extremely critical to the operation of the Bluing bath. If you don’t get this temperature control right, you will not achieve the correct Bluing colors.
To give you an example of the amount of bluing salt it will take to start a Bluing bath, it will take 40 pounds of bluing salt to 4 gallons of water, that is just about a 5-gallon bucket of bluing salt, and this will net you about 4.4 gallons of solution by volume. This tank is almost solid at room temperature and boiling at 292 degrees.
Each gun will spend 15 minutes to an hour in this tank depending on the type of steel used.
7. Flowing Water Rinse Tank
Same tank as above except that this time we are rinsing off the bluing solution. Then parts are inspected to ensure the quality of bluing is perfect.
8. Hot Water Rinse Tank
This tank is used to remove final traces of bluing solution, this tank is run at a vigorous boil parts are suspended for 5-10 minutes. Good water quality here is extremely important.
9. Water Displacing Oil Tank
Parts are then quickly placed in this tank to allow maximum displacement of trapped water. Parts are allowed to cool in this tank.
After the parts have cooled, they are removed from the water displacing oil tank. The parts are then hung on a curing rack. This is a very important part of the bluing process because the blue is very tender at this stage of the bluing process. We recommend a minimum handling time of no less than 24 hrs.
When curing is complete, we wipe excess oil off the parts with a soft cloth and reassemble the firearm.
A Note About Bluing the Inside of the Barrels
Tests were conducted by the government at Rock Island Arsenal several years ago on a series of blued bores to compare them to unblued bores. With this hot bluing solution method of gun bluing, it was found that the blued bores had a longer barrel life and better muzzle pressure. Although the results were very slight, it proves there isn’t a need to plug the barrel being blued to protect them. In addition, it would be very dangerous with the bluing solution operating at such super high temperatures to plug the barrel. The heat would cause the air in the barrel to rapidly expand, potentially causing the plugs to blow out with very explosive results.
From start to finish, most guns, from the time the metal is prepped to the water displacing oil will have spent about 2 hours in the bluing process. This may not seem like a long time, but we have yet to find very many people that can stand being in a very hot room with the parts for more than a few minutes. When the tanks are running at full steam this is a very harsh environment, face shields, respirators, full-length rubber aprons, rubber boots, long sleeve shirts and elbow-length rubber gloves are mandatory. We not only pride ourselves on our bluing skills, but we also ensure safety first. To give you a better example of the heat the process generates, imagine yourself in a room that has three gas burners. Each burner displaces enough heat that you could heat a large house. Our bluing area has a high rate of fresh air, which is the only way to keep the room a bearable 120.
We strive to put the highest quality of blue on your firearm. Keeping the firearm in “show-off” quality or allowing you to hand it down to the next generation of shooters and collectors.
The length of time required to perform these steps can vary greatly depending on the type, age, style, and condition of the firearm.
Our experience in this industry will allow us to answer your questions and take care of the majority of your needs. The services we offer may require us to see your firearm in order to quote a price. You can send us pictures via email and/or scanned pictures.