Metal Finishing, continued
Top quality you say? Yes, better than the current commercial hot caustic bluing done in professional shops. The process is fairly simple and requires no expensive equipment to get started.
It is important to keep in mind that the purpose of finishing the metal of a gun is to prevent corrosion. The most effective way to prevent steel from rusting is to protect it with a fine layer of rust. That is what bluing is all about. In addition, we get the added benefit of glare reduction and a fine appearance.
Early military rifles were kept in the white, or bare metal, because the soldier has time to constantly care for his rifle. The person who carries a gun for hunting or home defense needed a way to prevent corrosion.
Early gunsmiths began developing secret formulas to let them carefully grow a layer of rust on steel in order to create an effective barrier to further corrosion. These formulas included toxic and dangerous materials that induce a very fine grained oxide on the surface of the steel. They would remove the top surface of rust and repeat the process until the steel was a very fine brown in color and would hold oil as further protection.
Please allow me to digress a bit and explain the rusting process in a way that is not scientific, but makes a little sense to those who are trying to understand why we might rust a gun to prevent it from rusting. The damaging form of rust that we often see on a firearm is caused when oxygen reacts with the steel to cause oxidation, or rust. Think of the uncontrolled process being like a heavy weed growth with a thick stem and roots. It is unsightly and leaves the large stem and roots showing on the ground when we mow these weeds. This is similar to the pitted versions of rust we occasionally see on guns that have not been cleaned and oiled properly.
The controlled oxidation process is more like planting a putting green. We use special chemicals, humidity, and proper timing to produce a very fine layer of ferrous iron oxide on the surface of the steel with very fine pits into the steel. We then "mow" the iron oxide with steel wool to remove the surface layer and leave only the very fine pits in the steel to provide color and hold oil.
Bare iron is likely to oxidize when exposed to moisture, acids from the hands, or impurities from the environment, but the oxidation process slows quickly once the first layer of rust forms. The creation of a very fine surface layer of ferrous iron oxide on the surface of the steel is very effective in retarding further rust. This is especially true if oxygen can be sealed away from the steel with a substance such as oil.
Another form of accelerated oxidation that had been used in the early 1800s was to raise the temperature of the steel to around six hundred degrees where an oxidation process takes place and the steel turns dark blue in color. This process was known as Fire Bluing and was not only very difficult on large surfaces, but the penetration of protection was very shallow and easily worn off the steel. It is often used today to quickly and easily blue small parts like screw heads.
The oxidation process was an excellent way to provide a rust barrier on guns, but it left us with a brown color on the gun. Another good finishing process would be to change the ferrous iron oxide to ferro-ferric oxide, which is black in color. This is done by exposing the ferrous iron oxide to very hot water.
Modern gun companies began looking for a way to quickly produce the popular dark finish on their guns in an assembly line fashion, so the hot caustic blue method was developed. This process uses high temperatures and very dangerous caustic materials to quickly blue the gun. This process is way beyond the scope of most hobby gunsmiths and is best left to the professional refinishing shop.
A process that is within the reach of the advanced hobby gunsmith is to use a process known as black chrome. I have never seen the process used on firearms, but I am entertaining the notion of trying this process at home.
Most of the materials needed to do a fine job of rust bluing at home are inexpensive and most can already be found in the shop or kitchen. You will probably have to buy the bluing solution from Brownells, but the remaining materials are:
If you are planning to do a brown finish instead of blue, you will not need the distilled water or pot.
A decision must be made before we begin. I have successfully used two different browning solutions and like both of them, but there are different requirements for each. The Laurel Mountain Forge Barrel Brown and Degreaser does not require the acetone or rubber gloves to prevent oil contamination, but must be used in a reasonably controlled temperature and humidity environment.
The other solution I have successfully used is the Pilkington Classic American Rust Bluing Solution. This product is much more expensive and requires caution in not letting grease or oil on the steel, but does not require the humidity controlled cabinet.
If you are planning to brown or blue your parts on a warm and humid summer day, or planning to do a lot of bluing, then it would be best to use the Laurel Mountain Forge solution and make an inexpensive humidity and temperature controlled cabinet. On the other hand, if you are comfortable with careful surface contamination and need to work with browning in a less optimal environment, then the Classic American Rust Bluing Solution might be the better choice. I will say that the American solution does contain toxic materials that must be considered.
Both products do an excellent job of browning or bluing steel. I have used them both and find I was able to use either product in my warm and somewhat humid garage without the need for special cabinets. Rust based finishes should be done in the correct temperature and humidity for optimal results.
It is July in California and the outside temperature will be over one hundred degrees on most days. I will use the Laurel Mountain Forge product on this project, because it is less toxic, less expensive, and does not require the careful attention to surface contamination. I will, however, use the surface decontamination procedures just to illustrate how it is done for those who chose to use another solution.
Now that we have made the decision to use the Laurel Mountain Forge product for this article, I must prepare the surface of the parts to be blued. This is done by examining the parts for any damage and then filing or sanding out any blemishes.
We do not want to take the metal to a mirror finish when doing a rust bluing job. We only need to smooth the finish down to where there are no pits and we have the polish of 320 grit sandpaper.
I chose to use my Remington project gun to blue the barrel, loading lever, and the cylinder. The frame of the revolver will be nickel plated for a future article. This gun had the bluing removed over a year ago after experiencing a serious rust problem. The barrel has some serious metal damage and is a good candidate for this article.
I began by using 120 grit wet or dry sandpaper backed by a rubber eraser to start sanding the scratches out of the bare metal. I also use unscented mineral spirits instead of water in to keep the grit sharp and to keep the steel dust from clogging the grit. I do this by taking a small dish of unscented mineral spirits and brushing a little onto the sandpaper every few minutes. I use the unscented version of mineral spirits to reduce the odor that tends to linger in the area.
I use the 120 grit sandpaper to remove all of the surface flaws and get to clean metal, but the sandpaper adds scratches to the steel. If surface scratches are really bad, I will begin by draw filing the surface of the steel and then progressing to 80 grit emery cloth before advancing to the 120 grit paper.
After the rough scratches have been removed with the 120 grit paper, I usually switch to 220 wet or dry paper and repeat the process. Figure 2 shows the barrel after being sanded and is ready to be blued. The upper barrel is not going to be blued and will remain in the photos as a benchmark to help illustrate the color change in the parts as they darken. With the earlier marks cleaned up, I finally advance to 320 grit to finish the job. 320 grit paper seems to provide the best tooth for the rust bluing without showing any marks in the newly blued surface.
After finishing all of the parts that I plan to blue, I laid them out and prepared them for cleaning in acetone. Figure 3 shows the parts as they are finished and ready for cleaning.
I am using Laurel Mountain Forge Barrel Brown & Degreaser, because it is not toxic and contains a detergent to remove grease and oil before starting its work. Although it does not require degreasing of the parts, I still choose to rinse them down with acetone to remove any remaining grease or oil in the joints. This is done by applying acetone in a well ventilated space with a rag saturated with acetone.
With the parts all cleaned up and ready to brown or blue, lay them out on a newspaper just to keep them clean. Take a cotton ball in some tweezers and dip it into the browning solution and apply it evenly to the metal parts. I had clamped a wood dowel in my vise and slid the cylinder and barrel onto the dowel while they sat in the warm and humid garage to rust.
You should notice an immediate loss of shine as solution goes to work. Avoid any collection of liquid on the part as the rusting solution is also a rust solvent and may disturb any rust formation. You may also notice the dulling of the pat start to turn a light brown within a very short time as the solution starts creating the fine-grain rust pattern we desire.
Let the part sit in a warm and humid location for about three hours while you do something else, but avoid disturbing the parts. If you look at the parts and notice brown rust forming in some places, but bare steel in others, do not worry about this as it will be corrected in future applications of the solution.
Prepare the boiling water solution while the parts are rusting. I usually borrow a pot from the kitchen and use a burner on the bar-b-que outside to prepare my de-ionized or distilled water solution for boiling. If you are browning your parts, you will not need this step of the process so just ignore it.
Allow the parts to sit for three hours as a fine brown rust forms. This is creating the very fine grained pitting into the steel that represents the putting green smooth rust that is desired to hold the oil in the future. Figure 4 shows the parts as they should appear after about three hours of sitting and rusting. If you are browning your parts, skip the next instructions on boiling and move directly to carding.
Boiling of the rusted parts is necessary if you are bluing your steel. Skip this step if you are attempting to put a plumb brown finish on your parts. Using a kitchen pot with enough deionized or distilled water, bring the water up to a boil and get ready to dunk your parts.
Take each part and attach it to something that will allow you to remove the part from the boiling water without being burned. Caution--Boiling water is hot and you must make sure it does not come in contact with your skin through dunking or any other accident.
With the part securly attached to a wire or other tool, lower the part into the boiling water and allow it to sit for about five minutes. Remove the part and carefully blow the water from the part to make sure the part becomes dry. Be careful because the part is now very hot and any water coming from it is also hot.
I have laid the parts back out on the newspaper to illustrate how much different it looks now that the ferrous iron oxide to ferro-ferric oxide. It looks as if the parts have been dipped in a fine black powder, but that was the red rust only a few minutes ago.
Carding is the next step in creating our new finish whether we are bluing or browning our parts. In this step we use 0000 steel wool that has been degreased by pouring acetone through it to remove any residual oils.
Rub the steel wool vigorously on the red or blackened parts to remove the powdery surface rust. Depending on how much oxidation has taken effect on the first attempt, you will either see the metal return to silver, or you will start to see a noticeably darkened or red finish on the steel.
After the carding is completed, the first effects of the new finish should be visible. Figure 6 illustrates the first carding of the parts for my project gun. Notice how the test barrel at the top in the photo is now much lighter than the parts that have been treated.
The treated parts also have areas that have not shown any change. This is where steaks formed in the original solution treatment and should go away as more treatments are done on the parts. Do not worry if your parts do not have the same rapid bluing action as these as the solutions work at different rates depending on the temperature and humidity of the rusting room.
Regardless of whether you are browning or bluing, the next step is to apply the solution again and to let it rust again. This time there is a slight warning. This time it is necessary to just apply enough solution to dampen the part without it becoming wet. The rusting solution is also a rust solvent and it can remove some of the previous finish if too much is applied.
Another thing you will notice is that the second and later applications of the bluing or rusting solution will act much more slowly than the first application. This is because the first application of the material is already providing rust protection to the bare steel, which is no longer bare.
Allow the parts to sit for at least three hours after you have applied another very light dampening of the steel with the solution. When the three hours has passed, repeat the steps above to boil your parts if you are bluing the parts or going right to the carding process if you are doing either browning or bluing.
I was able to stop the process after four rusting and boiling sessions. The part developed a deep and rich grey/black color. I let the part sit for about a day and then oiled the parts. Do not oil the parts if you are browning the parts.
If you are browning the parts, then there is a different process to properly set in the color. Some people attempt to neutralize the rusting with a mixture of water and baking soda. I have never used this and have not had a problem. Instead, I mix a little burnt umber paint dye that is used by painters and I mix it 50/50 with Johnson's paste wax. I apply that mixture to the rusted and carded metal and it provides excellent protection to the new finish. About a week later, I usually oil the parts, which gives the metal a deeper hue.
The finished parts are either reinstalled on the gun or I will wrap them in a cloth that is saturated with oil to provide additional protection.
This represents either a very long day of metal finishing or it can be split across two days. I often allow the rusting process to take place overnight if it is on the third or later iteration as the process is much slower and more forgiving.
These metal parts will be stored for a few weeks until they can be assembled back onto one of my project guns. Now you can experiment with bluing or browning in your own home shop.