By: Steve Ostrem
I suppose it’s only fair to tell you that after all of the parts were polished and ready that I was a little apprehensive about the next step. Bluing the receiver, barrel, and other parts presented no problems, I’d already done a lot of that kind of work and expected no difficulties. In fact, that part of the process went very smoothly and the parts came out of the bath as black as coal after being immersed in Oxynate No. 7 (#082-007-940) bluing salts for about ten minutes at 290 degrees. All surfaces came out looking better than I had hoped. Even the pitting that remained around the lettering on the barrel and receiver was much less noticeable than I thought it would be. Everything was looking good to this point. The color-casing step, however, was another matter entirely. I knew the basics and had done some reading on the subject but had never attempted to do it myself. I wasn’t sure I liked the idea of heating my precious parts to red hot for an hour or more and then throwing them into a 55 gallon drum of water churning with air bubbles while allowing fate and fortune to determine the quality and look of the final product. Nevertheless, when the appointed day arrived it was too late to back out. I went ahead and picked up a Premier Color Case Hardening Kit (#080-951-500) for the project.
Before cartridge guns came on the scene, the only gun parts having any significant hardness were things like hammers, springs, and frizzens, plus the internal parts for the locks on black powder guns. As guns became more sophisticated, they relied more and more on moving parts and fired increasingly more powerful cartridges. The soft steel and iron then available were not always up to the task, and the alloy steels used today had not yet been invented. Thus, case hardening became a popular way to give surface hardness and wear resistance to mild steel in the 19th and 20th century with firearms manufacturers and industry in general. It also allowed soft, easy-to-machine metals to be used that saved on tooling costs and time needed to make the parts. Once hardened, the metal was glass-hard on the outside. This made wear surfaces much more durable and greatly increased the lifespan of many mechanisms, including guns. The hardness only reached into the metal a few thousandths of an inch while leaving the core as soft as before. This insured good shock resistance, which is the reason the locking parts on a rifle do not shatter after being case-hardened and exposed to the forces of the weapon being discharged. It also made the parts work more smoothly against each other without galling or wearing. The color imparted to the metal is a simply fortuitous by-product of the hardening process that gunmakers refined over the years until they were able to consistently produce the beautiful finishes seen on fine guns.
As color casing became more prevalent it was used in the manufacture of common grade working guns as well. If you break open Grandpa’s old double shotgun that has all of the finish worn off odds are you will find traces of case coloring somewhere, like where the barrels rest on the receiver or on some of the forend metal or other working parts. Even today firearms are being produced using the old methods to color and/or harden the metal. It is also possible to simulate these colors with a chemical process as Ruger® does on their Vaquero® series. These revolvers are made from modern steel and do not require the hardness that real case coloring would impart, in fact, it could make them too brittle to be safe. The process Ruger uses provides the desirable coloring while leaving the hardness of their receivers unaffected and keeping the cost of production down. It would be safe to assume that the growing popularity of cowboy action shooting has played a large role in the resurgence of the older firearm designs that look and shoot like the originals. We now have more firearms on the market exhibiting casehardening colors than perhaps at any other time in history. Just when you thought that everything was going to stainless, aluminum and plastic…
The parts we needed to color were annealed and polished as described in part one. The lever, bolt, buttplate, forend cap, hammer, and trigger were filed, sanded, polished and degreased. It is worth stressing that every part must be completely clean as any contamination can prevent the colors from turning out well. While the oven was heating up, we carefully put the parts into a steel, cylindrical crucible with a square, steel base welded to one end to seal it. The parts were surrounded with a 50/50 mixture of wood and bone charcoal so that none of them were touching the cylinder or each other. Banging on the side of the container with a hammer helped to settle charcoal and eliminate any voids in the pack. Any pocket of air can interfere with the parts taking color. When we could get no more charcoal to go in, we placed the cap on the cylinder, tapped it into place, put it into the oven and waited for it to come up to temperature.
The color case process is a complicated one and I’m not sure I could explain it properly even if I understood it. It is known that the act of quenching the hot parts in oxygen-rich water results in a chemical reaction between the calcium from the bone charcoal and the steam produced during the quench. It is believed that several other chemical compounds are momentarily formed when the metal hits the water and that they have an effect on the colors as well. Many materials have been tried in the pack over the years, but it seems that the calcium from the bone charcoal is the critical element that makes the bright, vivid colors that firearms aficionados find so pleasing. Mixing that with wood or some other kind of charcoal, such as charred leather, will add variety to the colors produced. Everyone has their own formula. That’s why Colt colors are different from those of L.C. Smith whose are different from Marlin and so on. As the oven heated up I couldn’t help but wonder what color, if any, my parts would have.
After the oven reached 1430 degrees, we got it regulated at that temperature and waited for the parts to cook for at least an hour to insure good carbon penetration into the steel. I remember taking a quick look through a small peep hole in the front of the oven door and seeing the container full of my parts glowing red hot in the dark. I asked Dave Bennets, Gun Tech extraordinaire and gunsmith in charge of color case hardening, if he thought my parts would come out with good colors. He assured me that he had no idea what was going to happen when they hit the water and that we would find out when the time came. He also cheerfully pointed out that parts can be seriously warped by the heating and quenching, thus making the quality and types of colors on the parts the least of our worries at this point. It was one of those moments when ignorance would have really been bliss. I took one long, last look at the glowing cylinder in the oven, and wondered if bluing might not have been the better option.
After the parts had been at temperature for a little over an hour, it was time for the big quench. A 55-gallon drum had been set up outside away from the building and anything else that did not need to get wet. The water was already quite saturated with oxygen from compressed air pumped into it via a copper coil in the bottom with many small holes drilled in it. Over that is a steel mesh basket to catch the parts when they are dumped. For best results, it is a good idea to let the air run into the water for an hour or so before any quenching takes place to make sure there is as much oxygen in it as possible. This oxygen needs to be present for the suspected chemical reactions required for coloring to take place at the moment of truth. More importantly, the bubbling also disrupts the cooling pattern on the surface of the metal and gives the colors an attractive mottled appearance as if they had been splashed or painted on; and that, as they say, is the whole object of the exercise.
 Wow! Look at all those colors! |
Now things started to happen pretty quickly. Gloves and eye protection were donned and the path between the oven and the quench tank was swept free of obstacles. This is where a little teamwork goes a long way. When Dave had the tongs in hand and indicated that he was ready, I opened the door of the furnace and held it while he grabbed the crucible. As soon as the glowing vessel was clear the oven door was closed and we walked quickly to the waiting water tank. As he put the crucible down beside the drum I picked up a strategically pre-positioned hammer and sharply struck the bottom of the lip on the lid to knock it clear. Then the crucible was immediately picked up, swung in a wood chopping- type arc over the tank and down toward the frothing water. |
| When the hinge area of the tongs struck the edge of the steel drum the crucible stopped suddenly and the contents were ejected into the quench resulting in a hissing cloud of steam and causing charcoal-enriched water to fly in all directions. After the hot tongs and crucible were set aside at a safe distance, we slowly lifted the steel mesh basket up to the surface to see what we had.
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As the parts broke the surface the buttplate was the first thing to catch my eye. It was beautiful! The trigger, lever, and hammer came out great, and the forend tip looked even better! My enthusiasm knew no bounds until I did a quick inventory. Weren’t there six parts in there when we started? I told Dave my bolt seemed to be missing. “Must be at the bottom of the tank” he replied without a trace of concern. I guess that was his way of saying that I got to empty the quench tank and put it away. Eventually the bolt did show up buried in soggy charcoal at the very bottom. Luckily, it seemed to be none the worse for wear. I carefully cleaned the parts and took them home for the last step. Luckily my wife was out of town, so I arranged the parts on one of her cookie sheets and popped them into the oven at about 390 degrees for about an hour to draw the hardness back just a little. After that, the oven was turned off and allowed to cool overnight. That gave me time to start assembling the rest of the rifle. The next morning the parts were removed and oiled prior to installation. About 30 minutes later I had the gun completely assembled except for one tiny little problem. That beautiful buttplate had warped slightly and was a little bowed in the center than it had been before. At this point I could either re-inlet the stock to accept the new curve, or try to bend my newly hardened, but now breakable part. Part of me wanted to go the quick and dirty, (but risky) route and see if the buttplate would bend. The other part said go for the sure thing and inlet it correctly- (more work). After sleeping on it I decided the next day to do the right thing and make the stock fit the plate. The possibility of breaking the part was too much for me to risk at this point. After all, who wants a two-piece buttplate on their Marlin? As it turned out the bend wasn’t that bad and very little work was required to make the things go back together. Now the gun was complete and looking good for the first time in many decades.
Buttplate was refit to the stock - a wise decision. |
Newly-colored forend tip with new magazine tube..
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On the whole, I was delighted with the way things came together, and with the newly colored components in particular. To be honest, I was a little disappointed with the colors on the bolt. Of all the pieces it turned out to be the least attractive, at least to me, with half of the outward side a beautiful blue pattern, and the rear half a less appealing gray pattern. Why it turned out that way we do not know. It could have been the way it hit the water, or the way it sat in the crucible while baking, or the mixture of the two charcoals packed against it, or possibly what phase the moon happened to be in on that day. Color casing is more of an art than a science, and predictable is a word not often used to describe the process. On the other hand, it is a very rewarding experience and a specialized tool that allows a gunsmith to restore and customize firearms in a way that makes each one a truly unique example of the gunmakers art. It is also worth noting for the gunsmith who may be interested in adding this skill to his repertoire, that the beautiful colors on fine guns produced by this process have the power to make grown men part with fistfuls of hundred dollar bills without batting an eye.
Bolt is acceptable but could have
turned out better. |
Colors on lever, hammer, and trigger really dress things up! |
Like custom checkering and engraving, case coloring adds to the value of the value of the gun. It also brings critical working parts back to the proper hardness for better durability. But like those two disciplines it requires skill and attention to detail to ensure a successful outcome. One big advantage color casing has over the other two processes is that any part exhibiting undesirable colors can be re-polished and done again to achieve the desired result. In that respect it’s very much like bluing. It does however, requires a willingness on the part of the operator to experiment and keep trying new things until a successful method is worked out. For anyone ready to make the commitment to learn this specialty the rewards are well worth the time and labor invested.
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The finished product, ready for action. |
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With the rifle completely assembled the next step should be to do a little aging and antiquing to make it appear closer to an original finish. I’m sure I will get around to doing just that…eventually. Right now I just cannot bring myself to attack that beautiful finish to make the gun look as it should for its age. The novelty of having an as-new appearing rifle that was made over a century ago is just too great a temptation to resist. Then again, perhaps if I take it out and use it frequently enough the problem will take care of itself. Come to think of it, this “new rifle” is like a blank sheet of paper ready to record a whole new set of adventures afield. Maybe some day it will be covered with scratches and wear marks that my kids and I will be able to look at and be reminded of all the fun we had taking that gun to the range and out in the woods after game. In fact, I think I will leave it alone and let nature take its course. From now on, I’ll consider this gun to be a work in progress.
Marlin Makeover - Part I
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