The ornamentation of metal surfaces is a vast and fascinating topic for metal bugs like jewelers and goldsmiths or gun manufacturers. Although the first works primarily with precious metals and the latter with a variety of steel alloys, there’s a lot of common ground. It is impossible to draw a clear line between them, because over the five plus millennia that humans have been processing metals, countless techniques have evolved, some of which are more straightforward than others.
Given this abundance, it is impossible to know every last one of these techniques, let alone master them all. For gunsmiths and goldsmith alike it is essential that they be able to apply those in demand by their clientele and grow from there. Let’s look at a few of the better known ones.
The great paradox in the subject of surface finish is that the most common finish for both precious and non-precious metals is the absence of any ornamentation or texture–polishing. Polishing is sometimes belittled as being plain and even hackneyed. To be sure, commercial items such as souvenirs are polished by industrial methods designed to handle volume. Then there’s the professional artisan, who has trained for years to attain the skills so they can polish without affecting the form or the crispness of contours and outlines. The difference between the two extremes is striking, and the lions share of the work—and thereby the cost—is not so much in the polishing itself, but in the preparation: the more skill and attention went into it, the tighter the polish.
Polishing the steels gun components are made of is usually followed by some sort of passivation process or another to increase the metal’s resistance to environmental factors. Base metals are defined by their one property: corrosion, hence the almost demeaning B-word that describes them. Since the Bronze Age, humans have put a lot of effort into finding ways that might mitigate, even arrest corrosion. Browning and bluing are methods that have been around for some time. Besides influencing steel’s chemical properties, they also impart an attractive dark brown and dark blue color, respectively, reducing glare and distracting reflections that could adversely affect the hunter’s vision.
Either method may also be used in combination with a brushed, or satin finish, just like with a piece of jewelry. With precious metals, however, a brushed surface texture can also be as plain as a neat sandpaper finish. Unlike industrial brushing, sanding by hand has the advantage that, if done with skill, minimally affects the form or the crispness of edges and outlines. Contrary to polished surfaces, brushed or sanded surfaces will diffuse light, thereby enhancing the perception of the metal’s color. This sometimes recommends itself with bicolor designs where yellow is combined with white gold, platinum or palladium. An additional benefit of a surface texture like brushing or sanding is that it masks wear marks and scratches. For precious metal jewelry that is potentially exposed to wear like rings and bracelets, this can be an appropriate choice.
The hardness of steels can be manipulated to much greater extent than with precious metals. Typically, steels are kept in their soft state during the manufacturing process so they are highly workable and then hardened, so they can perform their best. An ancient method is to diffuse carbon into the surface by exposing the steel to charcoal and other organic materials in a heated environment over a period of time, a method known as case hardening. Another one is nitriding, which was researched only a century ago. It has evolved into an industrial process involving a variety of different methods that allow for both case hardening and passivation at the same time. While traditional case hardening requires some surface reworking, nitriding does not, as it typically leaves behind a uniformly matte, gray surface that has an appeal of its own.
Precious metals and their non-precious counterparts can be combined by the ancient technique of inlaying the softer into the harder. Typically, this means preparing a recessed area in the harder steel and then fitting the softer gold into it before it is made to expand by forging. The steel is undercut at the interface and the gold locks into it as it expands. This combination of metals suggests, nay, begs for subsequent surface treatments like polishing, texturing, engraving, possibly even browning or bluing of the steel. The contrast in color and brightness between the dark steel and the bright gold never fails to draw attention.
If there were a list of endangered artistic techniques, you’d certainly find enameling at the top. Preparation is extremely time-intensive and it takes years of experience to get the necessary know-how to work with the real stuff that is vitreous and has the unparalleled bright, vivid colors of a fine gem. With enameling, a major key to success is the coefficient of expansion of the recipient metal. Vitreous enamel is essentially colored glass that is heat-fused to a recipient metal. If the coefficient of expansion between metal and enamel goes beyond a certain point, the potentially less elastic enamel will crack upon cooling. There is always a tremendous amount of tension between glass and metal from the contraction after firing, and even relatively small shocks can cause sound enamel to chip or crack.
Surface ornamentation of metals both precious and non-precious is a vast and fascinating field for designers, manufacturers and patrons alike. The combinations are virtually boundless, providing the professional artisan, be they gunsmith or goldsmith, with a huge playground on which to create the truly unique.–Robert Ackermann G.G.