Guncraft

Beauty,” wrote Victorian artist and essayist Eric Gill, “is an accident of right making.” What is true in the visual and plastic arts is equally so in the craft of old-fashioned gunmaking —and is particularly pertinent to traditional color case hardening.
    As explained in my first installment (May/June ’09), “right making” in the process of color case hardening guns is founded on time-proven metallurgical principles. By the application of heat, the process transfers carbon to the surface layers of low-carbon (or “mild”) steel from a surrounding carburizing “pack.” The carbon “case” —a glass-hard skin, in essence—is set in the surface by a subsequent drop in temperature when the red-hot metal is quenched in a liquid, such as water, brine or oil. The exterior is consequently resistant to wear and corrosion, while the core stays ductile to absorb the forces of firing—forces that otherwise tend to rend the action of a gun.
    Case colors—comprised basically of iron oxide and formed as a chemical reaction between hot metal, the carbon pack and the quench liquid—were once incidental to the hardening process but now are treasured for the decorative beauty they lend the gun.
    Like a sunset, each color pattern on a gun is unique unto itself—no two will ever be exactly the same. But within given metallurgical parameters there is ample opportunity for an individual craftsman to use his own judgment, skills and experience to influence and create results of dramatic variety, from the quality and depth of the hardening to variations in the colors—in their arrangement, intensity and hues, and the lively interplay of all thereof.
    Robin Brown, director and owner of British gunmaker A.A. Brown & Sons, learned his version of right making in the early 1960s from Ted Stokes, when Robin was a young man and Ted an old one. Robin’s mentor had learned his craft in the days when heating for color hardening was conducted in the open flames of a coke fire and the processes relating to it were secrets jealously guarded by its master practitioners.
    Ted, however, was a generous teacher and shared with Robin the old-time techniques he had learned during a life spent working at the Century Polishing & Hardening Co., which in the mid-20th Century was one of a couple of prominent color case hardeners within the Birmingham gun trade.
    Robin is no longer the brown-haired lad who joined the workbench at age 16 with his father and uncle by his side. His hair has gone gray, but his eyes still twinkle like a schoolboy’s and he remains, true to his training, a perfectionist in the old school of British gunmaking. “I was influenced greatly during my apprenticeship by, on the one hand, my Uncle Albert, a first-class actioner, and on the other by my Dad, a perfectionist when it came to freeing and finishing a new gun,” Robin recalled during my most recent visit to the Brown workshop, in November. “I was also apprenticed for five years under Albert Thompson, a master gun stocker. I was fortunate to be mentored by men such as these as well as Ted Stokes.”
    Traditional color case hardening consists of four major steps: bone meal preparation, the arrangement of the components in the carbon pack, the heat cycle and the quench. Though his techniques remain rooted in those taught to him by Stokes, educative powers of experience have led Robin to make improvements over the ensuing decades to virtually all aspects of the four-fold process.
    When a near-finished gun is ready for hardening, it is disassembled and its components polished a final time. Robin then thoroughly degreases the parts to be color hardened and prepares the meal—that is, he cooks off any remnant animal fats in it. Carburizing a gun in dirty meal otherwise leads to unsightly scaling, as does hardening metal with any traces of oil or grease on its surface or within its cavities.
    “In the old days when I was working with Ted, when we got in a fresh batch of meal we’d first experiment by color hardening different pieces of metal to make sure we were going to get the results we wanted,” Robin said. “We never knew exactly where the meal came from or the sorts of contaminants we’d find in it.
    “The level of flaking we’d see in those experiments told us how much meal prep we needed to do before hardening actual gun components. The quality of the meal back then was not predictable and was the grayest area of the whole process.”
This has changed for the better, as these days Robin is able to obtain the same bone charcoal that Scotch distilleries use to filter whisky. “There is much less grease in it,” Robin said. “Consequently, preparation is now easier and quicker.”
    Whereas Robin uses only bone charcoal, some American color case-hardening recipes add other carburizing materials—notably wood charcoal—to the pack. A pure source of carbon, wood charcoal can produce different ranges of colors and color patterns on a gun, as seen in the diversity of finishes on guns from each of the historical American makers.
    In recent years talented practitioners —such as America’s Doug Turnbull, Germany’s Jorge Schiller, and America’s late Dr. Oscar Gaddy and his disciples—have evolved a number of techniques that have been immensely consequential to the development of, and reproducibility of, colors and color patterns. These include any number of jigs, blocks, shields and mechanical fixtures that either retain heat or keep the carbon material close to the metal as it is quenched. The most vivid colors seem to come when components cool more slowly as they quench and also when the carbon pack remains enveloped around the metal as it falls through the quench.
    Robin’s methods remain almost alchemical by contrast and rely heavily on his skill in “packing the pot”—that is, Robin’s placement of components within the carbon pack and pot—to achieve desired colors and hardness. “The way in which I arrange the components affects the amount of heat they receive, how much carbon is absorbed and how fast the bone meal is washed away in the quench,” Robin said.
    “Back in the day when Ted was teaching me, we used copper wire to fix specially shaped pieces of steel to the backs of the lockplates to enhance color. But over time I’ve found this increases distortion.
    “I’ve come to the conclusion that wiring metal onto components is a bad idea. But that’s just my opinion. Others no doubt differ and have good results doing it.”
    Appropriate hardness is achieved when components are heated to critical temperature for a certain length of time in a given bone meal. The longer they are “soaked” in the carburizing pack at higher temperatures, the deeper the carbon penetration and the harder the resulting skin; but excesses in time and temperature carry with them greater risks of distortion and also increased brittleness. Careful packing of components, as noted, helps minimize these dangers, but experience has taught Robin that exact temperature control is equally critical for quality results.
    In Robin’s learning days the gas-fired furnaces at Westley Richards had automatic temperature settings, but they, in fact, lacked any real precision. “We’d set them for the temperature we wanted,” Robin said, “but in reality the range of heat was drifting up and down on either side of our setting. I found the high peaks caused more distortion.”
    Robin walked me to the machine-tool room that houses Brown’s furnace—a natural-gas-fired muffle furnace custom made in 1974. Today Robin eschews auto-controls; instead he manually sets for a certain temperature—between 750° C and 775° C, depending on the characteristics of the bone charcoal on hand—and carefully monitors the pyrometer to ensure “absolutely stable” temperatures. “You can’t go off and brew a pot of tea and forget about it,” he said.
    The heat cycle lasts about three hours from when Robin places the pot—a rectangular box of welded steel large enough for the components of one gun—in the pre-heated furnace to the time when he removes it. During the final 20 minutes, Robin drops the temperature by 10° C. “I found this decreases distortion,” he said. Before tipping the contents into the quench, Robin rests the pot outside the furnace an additional two minutes. “The steadying of the bone-meal temperature prior to tip seems to ‘bind’ the parcel of gun parts and bone meal during the drop from pot to water,” Robin explained. “That way the tip seems less explosive and more predictable.”
    Colors come during the quench, and if components hit open air before they meet liquid, they will “flash”—leaving unsightly gray blotches on their surfaces due to oxidation. To prevent this, Robin tips the contents of the pot into the quench from a height of about 1-1/2" above the water. A flashed component is hard, but if the blotching is visible, the part must be re-colored.
    You will see discussions of some practitioners adding ingredients—secret or otherwise—to the quench to enliven colors, or guidelines for holding water at a certain optimum temperature to affect same. Robin’s approach is decidedly elemental: “We just use cool water, fresh out of the tap.”
    Standard procedure does recommend oxygenating quench water for better colors, a procedure Robin follows. “We use a hose to create turbulence, which increases oxygen content,” he said. “But I personally don’t think you should have air bubbles floating in the water at the time of the tip. There is an increased risk of flashing, I think, and you get colors that just don’t look ‘right’ on a traditional English gun—too many bright pinks and oranges.”
    The latitude of permissible techniques and materials (as well as personal tricks of the trade) means that almost every hardener has a signature coloring style—or styles in the case of commercial hardeners like Doug Turnbull, who works with a wide variety of guns of different makes, models and designs and from many countries. Robin’s methods, by contrast, have evolved for essentially one gun: the Supreme De Luxe, Brown’s easy-opening “best” sidelock of modified Holland & Holland design, although he also re-hardens sidelocks and boxlocks from other British makers when he restores them.
    Robin smiles as he speaks of the “joy of colors” on a gun he has correctly colored, and for him correctness follows certain principles of pattern, placement and color. On Supreme De Luxe lockplates, for example, the darker colors—the blues and related permutations—will be nearer the centers, with grays, browns and tans radiating outward, the lightest shades predominating at the edges. A form of framing, this highlights the bolder colors and sets them off against the chocolate hues of the stock.
    “Generally we think there should be plenty of blues,” Robin said, “but the browns are very important as well. If you have too much blue and no browns or beige, it all begins to look rather dull and miserable.”
    Aesthetics are, of course, only half the equation in color case hardening—the carbon skin and its protective qualities will matter to the shooter long after colors have faded. Colors on a gun a century old may have rubbed off through use, but a properly hardened case will keep the metal largely unsullied by wear.
    The case itself seems surprisingly thin. Robin estimates that his are about .002" deep. “This is plenty thick to prevent wear,” he said. “If you go much deeper, I’ve found you run the risk of metal distortion.” Brown’s guns, it should be noted, are rarely built as “closet queens”—or collectors’ pieces—but instead are commissioned by a clientele that tends to shoot them hard and incessantly at driven game, year after year. I have seen any number of Supreme De Luxes with their stocks in tatters but their metalwork invariably as pristine as the blade of Excalibur.
    For all his time-earned expertise, Robin remains non-dogmatic about his methods. “I am not a hardener to the trade,” he said, “and I am not suggesting I’m the only one getting it right. However, over 40 or so years I have worked out processes that work for me and for the type of traditional guns we build. I like the colors we achieve, and I get a good, even case that is hard and stands up to wear and all with minimal distortion.”
    Back in the 1970s, when Robin’s father and uncle were still running A.A. Brown, British gunwriter Geoffrey Boothroyd noted this of the firm’s guns: “The end product is a result of the accumulated knowledge and skills of several generations of working gunmakers.”
    That is abundantly evident, in a more singular way, in the trial & error processes Robin has developed to empirically improve on the color-hardening methods he originally was taught by Ted Stokes in the early ’60s.
    “Art is skill,” Eric Gill wrote. “That is the first meaning of the word.” That art—and those guncraft skills—are exemplified in Robin Brown’s color case hardening.

Author’s Note: Special thanks to Robin Brown, Doug Turnbull and Jorge Schiller for their perspectives and assistance with this article. For more information on A.A. Brown guns, contact A.A. Brown & Sons, 01144-121-445-5395; www.doubleguns .co.uk.