Finishing

In watchmaking, the term finishing does not indicate a mere accessory final step: it is an autonomous discipline that divides sharply into two distinct areas, that of the movement and that of external surfaces, each with its own techniques, objectives, and quality hierarchies.

On the movement, finishing serves a dual purpose. The first is aesthetic: Côtes de Genève, perlage, colimaçon, black polishing, snailing, and guilloché transform otherwise anonymous components into surfaces that play with light in a controlled manner. The second is technical, at least in part: Côtes de Genève, for example, reduce reflections during inspection and assembly, while anglage — the beveling of the edges of bridges and plates — eliminates sharp corners that could trap debris. Côtes de Genève are wavy parallel lines engraved on plates and bridges; perlage creates a field of overlapping small circles, obtained with a rotating mandrel; colimaçon produces a concentric spiral, typical of the barrel and some rotors. Black polishing — also called mirror finishing — requires the surface to be brought to such a degree of planarity and polish that it reflects nothing: it is the most demanding finish and least tolerant of errors. Those who execute it poorly are immediately visible.

The Poinçon de Genève certifies a precise set of these finishes, along with other construction requirements: it is not self-awarded but verified by a third party. The RD118 movement by Roger Dubuis, often cited as a reference, counts twenty-one distinct manual finishes. Parmigiani calibers combine Côtes de Genève, perlage, and anglage even on the gold rotor, creating visual coherence from component to component.

On external surfaces — case, bezel, caseback — finishing works through contrast: satin against polished, linear brushing against mirror polishing. Sunray brushing on the dial radiates lines from the center toward the edge and completely changes appearance with the angle of light. Fumé is a gradient applied to the dial, from a light tone at the center to darker toward the edge. Mechanical guilloché — the real thing, executed on a rose engine lathe — engraves repeated geometries with depth and precision that no printing can replicate.

Surface treatments such as PVD and DLC belong to the category of protective finishes: they increase case hardness, modify color, and reduce scratches. They are not decorative in the traditional sense, but they have a decisive impact on the final appearance of the watch over time. A special case is hand-hammered finishing, which introduces an intentionally irregular texture on plates or external surfaces: each piece is unique, but repeatability is zero.