The Côtes de Genève motif is the best known of all the decorations adorning watch movements. Perhaps this is due to its name that initially seems both striking and somewhat strange, or possibly because it is so strongly present on movements. Whatever the case, this pattern traced on the smooth surfaces of mechanical (and indeed quartz) movements is a familiar sight on the watchmaking scene – to the point where one almost forgets that finishes are not a purely aesthetic element.
Strictly speaking, Côtes de Genève are scratches. Controlled, systematically and carefully made, but scratches nonetheless. When it emerges from the machining process, the brass from which movements are made is flawed and scratched. After being polished and sandblasted to varying degrees of fineness, the metal undergoes a galvanic plating treatment with gold or rhodium, which gives it a distinctive grey colour. Thus attired in its new colour, the component is placed under a lathe performing a rotational, translational (parallel) motion. A tool head in wood or sandpaper spins on its axis as well as along dedicated rails. It is bent slightly forwards and draws a lengthwise stripe, as well as tracing a finely brushed semi-circular motif. These tiny scratches catch the light and hide the last traces of machining. Côtes de Genève also come in a circular version, for which the tool is placed on a rotating carrier with no translational motion.
The Côtes de Genève motif really came into its own in the early 20th century. And while it was apparently born in Geneva, it soon found its way throughout the watchmaking valleys. It has a three-fold purpose. The first is simple: sliding a component along a specific axis is the simplest decorative process and the most straightforward to automate. The second is to enhance the beauty of components. The very fact that it has become so widely used might obscure the obvious fact that meticulous execution and favourable lighting combine to make Côtes de Genève extremely appealing. Especially since they are now often clearly visible. While traditional Swiss watchmaking generally uses this form of decoration to adorn bridges, which are on the back of the case and thus the wrist side, the increasing popularity of sapphire crystal ‘exhibition’ case-backs has brought Côtes de Genève to the forefront of mechanical aesthetics.
However, as is often the case in watchmaking, enhancing aesthetic appeal is not a purely gratuitous operation. While Geneva’s watchmaking has long been known for its refinement and its ornamentation, its Côtes or stripes also serve a third purpose, since these scratches create a rough surface that picks up dust. In the age of pocket watches with open backs, this ‘particle trap’ was about as much use as a poultice on a wooden leg. But as cases gradually came to be closed and thus far more airtight, Côtes de Genève took on new importance. During the early phases of industrialisation in the watchmaking valleys, the hunt for dust was simply no longer practically feasible. Côtes de Genève were a partial response to this problem, since this finish served to capture the microparticles flying around the workshops and to prevent them from settling in lubricants and on movement jewels or pivots. So useful did they prove that the German watchmakers of the Saxony region also adopted them, albeit under the name of Glashütte stripes.