MatteFinishes: Lackluster by Design

Gold doesn’t have to glitter to be gold. In fact, many jewelry manufacturers deliberately trade high gloss for low luster in order to give their pieces a muted appearance. Since gold is, by nature, a metal that loves to shine, keeping it from doing so requires skillful mutilation with various abrasives.

The art of imparting a dull or non-reflective surface to gold (or any normally lustrous metal, for that matter) is called matte finishing. Metal workers use several means and methods to subdue the metal’s glow. Nevertheless, all of them boil down to some form of scratch texturing.

Basically, explains Gregg Todd, a former Paris Junior College instructor who is now training coordinator with Stuller Settings Inc., Lafayette, La., there are two kinds of matte finishing: directional and non-directional. The former involves making very fine lines in metal while the latter involves either bombarding it with fine particles or punching in tiny indentations.

Directional finishing
When going for the intentionally lackluster, the choice of finishing tools depends on the degree of fineness and uniformity one wants for a metal’s texture. That’s why jewelry arts trainers like Todd generally talk about three types of surface texture in connection with matte finishes: fine, medium and heavy. Fine means satiny; medium, sleepy; and heavy, coarse. The differences are apparent when one sees examples of these finishes side by side.

Not to seem sexist, but fine directional finishing is what once might have been called feminine while coarse directional finishing is what might have been described as masculine. However, since we live in an age of unisex ear piercing, it is probably advisable to be more gender-neutral. So let’s just describe the fine-to-coarse continuum as velvety to virile.

No matter what the desired texture, a directional finish involves “running an abrasive material lateral to the metal’s surface,” explains Curt Hensen, product manager of Rio Grande, Albuquerque, N.M. To achieve what are variously known as satin or brushed finishes, the choice of finishing tool is usually a wheel made of either fiberglass in rubberized form or aluminum woven into fibers reminiscent of Brillo pads. However, in the last few years, wheels made of nylon fiber have gained in popularity, according to Hensen, for two reasons: “One, they are easier on workers than wire-brush wheels and, two, they allow more control of texture fineness.”

For slightly less fine but deeper and longer-lasting matte finishes, jewelry workers use sheets of emery cloth with various grades of grit on them. For flat surfaces, they glue these sheets to a workbench and give metal areas they want dulled a vigorous rubdown by hand. For curved surfaces, they wrap the emery cloth in strips so it forms a loosely raveled ball and place it on a rotating spindle against which the piece is pressed. “The primary advantage of an emery finish is greater wear ability,” Todd explains.

In cases where pieces require high contrast between lustrous and non-lustrous metal surfaces, or where a rough-hewn effect suitable for a Marlboro Man is wanted, the most popular scraping instrument is known as a heatless stone-used to remove plaster investment from castings. This somewhat misleading term refers to a hard grinding wheel made of silicon carbonate that gives a coarsely textured look. The wheel is called “heatless” because it runs very cool relative to other hard abrasives, something that endears this material both to workers
and work safety officials.

Non-directional finishing
When a matte finish is created either by bombarding or punching a metal’s surface, the end-result is said to be non-directional. In essence, these methods
involve indentation, for which many mediums are used.

The best-known non-directional finishing technique is called bead blasting. This method involves shooting various-mesh glass, aluminum oxide, silicon carbide or plastic beads at a metal with compressed air to create an evenly dimpled surface a bit like that of a golf ball. The pressure with which these beads are expelled determines their penetration while their size determines the overall fineness of the finish. When talking about bead blasting, many jewelers speak of it as if it were synonymous with sandblasting. Be warned that there are important differences between the two methods. According to Alan Revere, director of San Francisco’s Revere Academy of Jewelry Arts, sandblasting is a harsher treatment, which abrades metal surfaces, leaving them very porous. This, in turn, makes them prone to dinginess and tarnishing through the buildup of various body oils and chemical agents. As a result, sandblasting is a no-no for metals like silver. Bead blasting, on the other hand, both burnishes and hardens metal surfaces, leaving them highly resistant to dulling and discoloring.

When larger indentations are desired, various methods of a technique known as stippling are used. In a nutshell, stippling is a metal worker’s version of pointillism, a finish composed entirely of dots. These dots are rendered most often by either a pointed hammerhead or a ballpoint-tipped punch held by hand or attached to a flex-shaft. In the latter case, you have, in effect, a miniature jackhammer. “With machine-stippling,” says Todd, “you can get anywhere from 600 to 800 punches per minute.”

Besides offering greater speed, machine stippling ensures an even density and diameter to metal pricking as long as the worker sees to it that the process is administered evenly over the piece’s surface. “The point strikes at a constant rate and with constant force, making it ideal for a uniform look,” Todd notes, then adds: “If, however, you want some variation of appearance, use of a hand piece is probably a better bet.”

Modern Jeweler, June 1994
David Federman | 800-759-9997 | (fax) 800-616-9997