Gun bluing is a traditional way of protecting firearms from rusting, by actually rusting them in a controlled manner!
Bluing is a controlled rusting process; it is not a coat of paint or a finish. It is superior to applied ceramic paints, like Cerakote and Duracoat, because it actually changes the surface of the metal. It does not allow for intricate patterning or colouring, but if you’re not looking for BLING!, but for actual long lasting protection, then controlled rusting processes like bluing & browning may be right choice for you. Bluing helps protect the steel from random corrosion by causing the steel to rust in a controlled manner. Aluminium or steel alloys that don’t have enough steel in them cannot be blued. In some cases (especially with revolvers), even though the cylinder, barrel and small parts are steel, the frame is made out of aluminium or an alloy. One simple way to figure out if you can blue your frame is to check and see if it has any pull to a magnet. If it doesn’t, most places will either Cerakote or Duracoat them for you without even asking, but the price for having the parts ceramic painted will not be included in the bluing price, because it is another service. So make sure you check your firearm before sending it out to a shop, so you know what to expect price-wise. Let’s talk about what types of bluing are available on the market and roughly what cost you should expect, versus quality and life span. First of all, metal prep. Metal preparation is extremely important. As opposed to coatings like ceramic paints, when it comes to bluing, everything that is on the surface of the metal will be visible without prepping the metal properly in advance. To begin with, all rust needs to be removed. No shop will contaminate their bluing tanks with metal that has rust on it, even if the customer does not understand the importance of having the rust removed. No matter how light the rust, bluing will not eliminate it. All signs of pitting and rust need to be carefully removed and polished out. The next step in prepping the metal will be, after all rust and pitting is removed, to bead blast the metal. This will give your metal a matte look, which is not fancy, but it is decent and acceptable as an effective metal texture under the bluing. You will still see some machining marks on the metal, so depending on the grade of your firearm, you might want to address them. Polishing the metal for bluing is one of the hardest services to sell, because most of the times, people really believe that they will not be able to see any marks under bluing, but it is actually not the case. In our experience, if someone decides to have all the metal polished and prepared properly, they are looking at about 10-16 hours of manual polishing for long guns, most long guns being between 12-14 hours. Most gunsmithing shops will offer a discounted price for polishing time, because when it comes to polishing, although it is necessary in order to obtain the “better than original” quality, it can get quite costly, depending on the original condition of the firearm and type of firearm. For instance, double barrels will take longer, and even a small revolver that has seen some really rough days will need 10+ hours of polishing for “better than original” condition. But if you do want to remove all rust, all pitting and all machining marks, expect at least 10 billable hours of polishing for long guns. Due to the level of precision required for polishing under the bluing, this type of polishing is not done with a wheel, but manually. In most cases, your gunsmith will ask you how many hours of polishing you’re willing to invest in your firearm, so you can either decide your invoice based on the quality of work or the finished product or on the budget available. Some shops also offer the “DIP” option, which means that if you choose to prepare the metal yourself, they will do the bluing exclusively, based on a liability release form that you sign. This form will most likely include a loss of any warranty clause – and rightfully so. If you are sending your project in for a “dip”, the shops do not do any metal preparation for you. Your item will be expected to arrive at the shop completely rust-free and polished to your satisfaction.
Preparation should include stripping old bluing, then bead blasting with an abrasive (e.g. glass bead or aluminum oxide) to remove rust, followed by polishing from lower to higher grits. It is important that you properly oil and package your prepared metal, as surface rust can form in a very short period of time, especially in transit environments.
When the shop will receive your firearm, they will evaluate it to be sure there is no rust present, and then run it through the bluing tanks. If rust is present they will contact you regarding your options. Types of bluing:
1. Rust Bluing
Rust bluing is an older bluing process that is not used much anymore. It involves a process of causing a steel gun part to rust by applying an acid solution. After the part rusts, the acid is neutralized with boiling water and the rust is scrubbed off, leaving a blued finish. Many antique firearms were finished with this method, as industrialization was not yet such a big part of our lives. Rust bluing is better than Hot bluing, it lasts a lot longer and the process of rust bluing is also taking longer than hot bluing. The process is time consuming and complex: The acid solution is applied and the parts are placed in a temperature and humidity controlled environment to grow the rust for 12 hours. This process must be repeated every 12 hours until finished, if not, it can ruin the finish of the metal (it can cause it to start pitting). It usually takes about 10-14 cycles of 12 hours for a shotgun to be blued, so the high price for this service is found in the precise timing and availability around the clock to monitor the process and change and neutralize the acid every 12 hours. This labor intensive process is not used often nowadays because most gunsmithing shops have either lost the know-how or the clientele interested in spending good money on high-end rust bluing. This type of bluing is the best type of bluing available on the market, and since most firearms are hot blued not rust blued in factories, the condition of the firearm will be better than original when the owners opt for this option. This bluing will last the longest. Rust bluing costs on average twice as much as hot bluing. 2. Hot Bluing/Salt/Caustic Salt Bluing/Factory Bluing
Hot bluing uses a heated alkaline solution. Potassium nitrate and sodium hydroxide are common ingredients in this process. The hot solution is applied to the steel parts of a gun, usually by dipping the parts into the solution. When completed, hot bluing provides a tough, attractive look. This is the type of bluing you will find on factory-blued firearms. The factory bluing process hasn't changed much over the years; however, the factory bluing has a shorter life span than traditional rust bluing. Hot bluing can destroy solder, so most gunsmithing shops will refuse to take the risk of hot bluing your soldered firearm or parts. Depending on the salts and solder alloy used, your soldered firearm might not suffer when you take it in to one shop, and decades later when you take it to another shop (or even the same shop that changed the salts), it might get damaged - so just because you were able to hot blue it once, it doesn't mean it will work the second time. Most shops will either ask for a liability release form or will refuse the service. Brazing on the other hand, can go through the salts, but will not get blued. This bluing is a good durable finish, if you purchase a good gun, but will not be as good as the rust blue.
Cold bluing is used for cosmetic touch-ups of previously blued firearms. You can find a myriad of cold bluing solutions at gun stores and online for touching up your blued guns. Cold-bluing solutions usually are sold in small bottles, and are applied with a brush-type applicator. Sometimes they are lightly heated after application, to increase their durability. Cold bluing is not nearly as effective as a protective coating as hot bluing, but for small cosmetic touch-ups, it is ideal. Cold bluing cannot be done to the entire gun. It simply wouldn't look good enough and wouldn't last long enough, although you can buy kits that are advertised as being a good option for a DIY; in fact, it just doesn't last.
Fire Bluing a.k.a. Heat Bluing or Nitre Bluing
Not to be confused with hot bluing, fire bluing is the process of heating a polished steel part until the surface of the metal changes color to a deep blue. It's not as durable as hot bluing, but like cold bluing, can be easily done at home. It produces a colorful and attractive finish, ideal for smaller gun parts or restorations. Fire bluing is sometimes referred to as "heat bluing" or "nitre bluing".