Slow-Rust Bluing: Science or Alchemy?

Life, if one takes the time to look, is full of wonderful little pleasures. Be it meeting anew grandchild, watching a spectacular sunset, listening to an elk bugle on a frosty Montana morning, or a quiet walk in the woods with a special someone, wherever you choose to seek those good feelings you’ll find them if you just look.

In addition to the aforementioned, one of the little pleasures that ranks close to the top of my list is seeing a finely crafted firearm’t he graceful lines, the grain of the stock, and the balance as you bring it to shoulder. But to my way of thinking, the characteristic that most enhances that firearm and speaks to me of quality and beauty is the finish that has been applied to the metallic parts’ the bluing.

You only have to walk the isles of a gun show or view the gun racks in a hunting camp to get a notion of what I’m saying. Granted, the first thing that might capture the attention is a nicely figured piece of wood. But as you watch a person pick up a gun, where does their attention go and linger the longest? The metal to wood fit and, yes, the bluing.

The customers who come through my shop always leave with a smile on their faces, but the thing that really lights up their eyes is the first glimpse of that old "clunker" that only weeks ago was bouncing around in the bed of a pickup, now sporting a fresh and gleaming new blued finish. The finishing and refinishing of gun barrels and other metallic parts with rust bluing has been around along time. The earliest techniques were probably a carryover from the time-tested treatments applied to body armor and swords.

As with anything else, this technology has progressed through its own evolution, as attempts were made to speed the process, improve the appearance, reduce the cost, and increase the durability. Today, the customer can choose from a number of finishes ranging from browning, to Parkerizing, cold-bluing, nitre bluing, hot-bath bluing, even to nickel and chrome plating, painting, and anodizing. Whichever process is chosen, there are two main reasons for the finish: protection and appearance.

I think everyone understands the appearance aspect, but the protection requirement may not be so readily apparent. When left in the raw state, iron and steel have a nasty habit: they oxidize (rust). If neglected, any raw iron or steel will quickly become unsightly, and will eventually destroy itself. Guns are no exception. The These include screwdrivers and punches for disassembly, files and sandpaper for buffing, compounds for metal preparation, as well as steel wool and fine wire brushes for carding.

The author’s first slow-rust job was accomplished with a length of capped-off drain pipe and a Bunsen burner. A Coleman stove works great. Careful measurement, mixing, and use of the proper mixing and storage containers are mandatory. treatments mentioned are applied in order to reduce or eliminate iron’s and steel’s mad dash toward total entropy.

The way to retard or eliminate this natural process is to alter or cover the surface of the metal effectively, thus protecting it from the actions of oxygen and reducing its direct contact with water, which accelerates the oxidation process.

Interestingly enough, if we exclude plating, Parkerizing, and painting (which gain their effectiveness by coating the metal), the "bluing" methods used to protect the metal take advantage of those same destructive processes which, if not controlled, would lead to the total ruin of the firearm. Specifically, I’m talking about the tightly controlled oxidation of the surface of the metal. In essence, the bluing process allows the firearm to rust in order to protect it from rust.

Having said that, it may be clear that any substance that will cause rust can be used to blue or brown a firearm. Simply letting the bare metal "sit" exposed to the air is sufficient to produce a blue or brown if the process is controlled. This approach is certainly not practical, since a great deal of time is needed and the "control" referred to is particularly difficult to achieve, leading to something far less than the desired result.

Substances which have historically been used to speed up the process include table salt, blood, and urine, but still require more time than most gunsmiths would want to spend and produce results that are anything but predictable. The bluing and browning concoctions on the market today pretty much eliminate the concerns of time, predictability, and an undesirable end product. That doesn’t mean, however, that there aren’t tradeoffs to be considered when choosing among them.

Cold blues, for example, are by far the fastest and, in my opinion, are very good for small parts. However, unless extreme care is taken, attempting to use one of them to blue an entire gun can produce results that are less than spectacular. Hot bluing, the hotbath method used by most firearms manufacturers, produces a very uniform and attractive finish (albeit more black than blue) in a relatively short amount of time.

The drawback is that the hot-bluing process requires a considerable investment in equipment (salts, tanks, heat sources, buffing equipment, protective clothing, and so forth) which makes it impractical for the individual or small shop that does an occasional bluing job. Slowrust bluing, on the other hand, takes more time than other processes, but requires less equipment and produces a more lustrous finish than the hotblue method and produces a more durable and uniform finish than any of the cold blues I’ve tried.

When you look at a fine Belgium or English firearm, you’ll understand the visual appeal of the slow-rust process. The slow-rust bluing process employs the repeated application of an oxidizing agent, a "rest period" in a warm, humid environment, and the subsequent removal of the accumulated oxidation (rust) between each application. The entire process can take from three to 10 days, depending on the particular steel and the environmental conditions (temperature and humidity) in the shop.

Thus, the process is indeed slow, as the name implies. Metal preparation and the avoidance of grease and oil contamination during the bluing phase is critical with any bluing process, but is particularly important for slow rust bluing. With slow-rust bluing, there’s no substitute for care and attention to detail. After complete disassembly of the firearm, the process begins by systematically preparing the metal surfaces

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for bluing. If the gun is in really bad shape, with pitted and rusted surfaces, draw filing (striking) the barrels with a fine to medium mill file should be the first step. If necessary, a rust remover such as Steel White (available from Brownells) can be used prior to draw filing. This step will greatly reduce file clogging caused by fine rust particles. To prepare the file, draw apiece of chalk (yes, the kind used to write on blackboards) against the file’s grain, thus filling the teeth with a layer of chalk.

This will greatly reduce file clogging and ease cleaning with a file card. With the barrel (or other part) to be filed held firmly in a vise, lay the file on at approximately a 45-degree angle and with light downward pressure draw the file toward you the full length of the barrel. If done correctly, this will create a very tiny "flat" where metal was removed. Rotate the barrel and repeat. Continue until all rust and pits have been removed, going slowly and only removing enough metal to get rid of the pits.

Don’t concentrate the filing in one location or depressions or flats will be the end result. Coating the teeth of the file with chalk reduces clogging and simplifies cleaning of the file. Always use a "backer" (thin, flat piece of wood) behind the abrasive paper or cloth to prevent "washing-out" screw holes and to keep flat surfaces flat. On barrels, backers are not necessary. Instead, a modified "shoe-shine" stroke can be used.

Once the pits have been removed, you can begin polishing, starting with the coarser grits (120 or so). Again, use a "drawing" action along the long axis of the barrel or other part until all of the scratches and flats from draw filing have been removed. If you have access to polishing wheels made of stitched muslin, Brownells Polish-O- Ray is a good alternative to the above. Great care is needed to avoid washing out screw holes and stamped lettering or rounding off corners.

Anywhere this is likely to happen, I prefer to use paper or cloth abrasives and a wooden backer. Repeat this process in progressive stages to at least 320 grit, with 400 grit being better. Finer grits are neither necessary nor advised. This level of polish will give a fine satin finish and allow sufficient "roughness" to give the bluing agents a "bite" on the surface.

Once this stage is reached, going over the finished surface with an oily wire wheel or steel wool (again on the long axis of the part) will blend any remaining abrasive marks and highlight any imperfections you may have missed. You can purchase many different commercial slow-rust bluing agents or you might choose to mix up your own agent. Two very good sources for all kinds of bluing-agent formulas are Gunsmithing by Roy F. Dunlap and Firearm Bluing and Browning by R. H. Angier (both published by Stackpole Books).

I’ve tried many recipes, but the one I settled on years ago and the agent that I currently use in my shop is a variation of one from the Dunlap book, called "the Niedner cold blue." This is where the alchemy and science merge. The formula for the Niedner blue is: 2.5 oz. Nitric Acid 2 oz. Hydrochloric Acid 1 oz. Wire Nails 30 oz. Distilled Water You shouldn’t have any trouble finding wire nails and distilled water. The hydrochloric acid I use is 37 percent, and the nitric acid is 69 percent.

Check your phone book or with your local drug store or chemical supply to find local sources. (If you’re forced to purchase acids that are weaker’m ore dilute’you can reduce the amount of water you use accordingly.) Before we start talking about mixing acids, there’s something you need to remember: When diluting an acid, always add the acid to the water’not the other way around.

Diluting an acid creates lots of heat; if you add water to the acid, the water can boil instantly, spattering concentrated acid over a wide area. This is obviously a

Squeeze it out; too much solution in the cotton will cause runs which cause blemishes which are very difficult to remove. Application should be in long, lengthwise strokes running the full length of the barrel or part. hazard for you, as well as anyone or anything nearby. According to Dunlap’s instructions, the acids should be mixed in "a large crock or glass container outdoors." I use a large Pyrex beaker. (My wife frowns on my using her twoquart Pyrex measuring cup).

You want to use Pyrex, because a great deal of heat is produced in the process, sufficient to crack ordinary glass jars. Once the acids are mixed, the nails are added, just a couple at a time because the resulting reaction is fairly violent and would probably result in a boilover if all of them were added at once. Actually, I depart from the Niedner recipe in that I dissolve all the nails the solution will take.

What I am after is a totally saturated iron solution which assures the finest "bite" on the metal to be blued. After all the nails are dissolved and the solution has cooled, slowly add to the distilled water. All of this should be accomplished with great care. You’re dealing with very strong solutions that can produce severe chemical burns and or poisoning.

Therefore, it’s imperative that you wear eye protection, rubber gloves, and protective clothing. (I always wear a rubberized lab apron when mixing this solution.) I would also suggest that you read both Dunlap’s and Angier’s cautionary notes before attempting to mix this or other bluing solutions. I store my bluing solution in brown, capped and well-marked reagent bottles in a location not accessible to anyone but myself.

Prior to starting the actual bluing process, the parts to be blued must be cleaned of all grease and oil. There are several suitable agents on the market for this purpose, but the one I like best is Brownells Dicro-Clean No. 909. This cleaner comes in 8-pound and 24pound containers and has an operating temperature of 180 degrees.

If you only blue once in awhile and don’t need a large quantity of cleaner or don’t want to use a heated-bath cleaner, I suggest you consider one of the liquid degreasers available in smaller quantities that can be used right out of the bottle. The object is to end up with "surgically clean" parts. Any trace of oil can ruin an otherwise great bluing job.

This is not as important a consideration with hot bluing since the sodium hydroxide in the bluing salts will "make soap" out of very small trace amounts of oil, but with all the cold and slow-rust blues, cleanliness is crucial to a satisfactory end result. From this point on in the process, I wear clean (and I mean clean) cotton gloves. I use degreased wire parts hangers (black-iron stove-pipe wire or coat hangers work well) and degreased hardwood dowels to handle all parts.

When applying the bluing solution, I wear latex surgical gloves, available at any drug store. Do not touch any of the parts that will receive the bluing solution with your bare hands. For barrels, drive an appropriately sized dowel into the bore from both ends. This effectively seals the bore protecting it from the hot water of the bath and serves as a place to grab without touching the surface of the metal. Small parts can be suspended from loops of wire.

Pour a small amount (an ounce or two) of the bluing solution into a small wide-mouth glass container (baby-food jars work well for this as do 250ml beakers if you wish to play the chemist). Wearing rubber surgical gloves, dip a cotton ball into the solution, squeeze most of the solution out of the cotton so that it is wet but not dripping, and using long strokes (from one end of the barrel or part to the other in a single motion) apply the solution to the part or barrel. Rotate the barrel and apply another swath.

Don’t start and stop the application midway on apart, and don’t go back over the barrel or part unless you do the whole thing. Trying to "spot ap-

Don’t fret, however; the boiling and carding process will convert this ugly duckling into a thing of beauty. Note the wooden dowel driven into the barrel to keep water out of the bore during boiling. ply’ the solution will cause blemishes, which will show up in the finished product. Continue doing this until the entire barrel or part is covered. Set the parts aside in such away that the "blued" parts come in contact with nothing.

For small parts, I suspend them by their wires; for barrels, I stand them in a rack so that only the wood dowels contact the supports. Here in Michigan, the ambient humidity is normally high enough that sufficient moisture is not an issue. In drier climates, a "humidifier box" can be constructed. This can simply be a wooden box large enough to accom- Swatches of steel wool can be wrapped around toothpicks or splinters of wood to get into those places that brushes won’t reach.

All materials used for carding must be thoroughly degreased prior to use. To speed the carding procedure, a buffing head with a fine iron wire wheel can be used. Carding by hand works just as well, but takes a little longer. modate barrels, receivers, and small parts into which wet towels are placed. The wet towels will provide the water vapor necessary to raise the humidity and speed the chemical reactions. The parts should be allowed to sit and rust for three or four hours.

At the end of this period, the parts will look like the dickens, with various colors of gray, black, yellow, and rusty red. But despair not, this is normal. During this waiting period you can set up the tank for boiling the parts. I like to use distilled water in my tank, thus eliminating any concern about hard or soft water, chlorine, and other chemicals. About a half hour prior to the end of the rusting period, start heating the water.

Once a vigorous boil is achieved, suspend all the parts in the water and allow them to boil for about 20 minutes. For the chemically curious, the reaction on the steel parts produces ferric oxide, which is brown. Boiling, in addition to softening the scale making it easier to remove, converts the ferric oxide to ferro-ferric oxide, which is also known as black oxide. Why mention this? In the past, I’ve taken advantage of both of these properties.

If I am working on an old (or new for that matter) blackpowder muzzleloader, I want the finish to be a rich "plum brown." To get that brown coloration, I simply do not boil the parts. If the firearm is to be "blue," then I boil the parts to take advantage of the blackoxide conversion. Once the parts have boiled for the requisite period, they are removed from the bath and allowed to cool, making sure they are protected from coming into contact with anything

that might contaminate them. When cool, using a variety of fine wire brushes (or wheels) and 00 or 000 steel wool, I card off all the rust and scale. Under all this will be revealed the beginning of the blue you are trying to attain. When all the scale is removed, replace the wet wood plugs with dry ones, apply another coat of the bluing solution, and let it react for another three or four hours. Then boil the parts and card again. Repeat this process until the desired level of bluing has been achieved.

This can be anywhere between six and 10 or more applications, depending on the hardness of the steel. When the desired color is reached, conduct the last boiling and carding, apply a good grade of gun oil, and allow the parts to set for a day or two. After that, wipe the excess oil off with a soft clean cloth and admire the deep rich blue all your labor has produced. Finally, reassemble the firearm, call your customer, and invite him to view the beauty you have bestowed on his now precious rifle or shotgun.

He’ll think you are indeed an alchemist and that you’ve found the philosophers’ stone. Conclusions Slow-rust bluing is admittedly more labor intensive than other forms of bluing used in the industry, but it definitely has its advantages. For the one-time bluing job you might want to do on a personal gun, the cost of the setup is considerably less than conventional hot bluing and the results are more predictable than "bottle" cold bluing.

For the gunsmith, it opens Then it’s time to sit back and relish the work of art you’ve created for your customer. Note: the 410 shotgun shown here was blued 35 years ago by the author. After much use by children and grandchildren, it looks as good as it did the day it was blued. the door to refinishing high end guns that were originally blued by this process and allows him to blue those old soft-soldered doubles that can’t be blued in hot-bluing salts (unless your objective is to end up with two single barrels).

For me, the real benefit of slowrust bluing is that I can produce a metal finish that is far superior in both appearance and durability to other methods. And more than that, it allows me to experience another one of life’s wonderful little pleasures. I