Black finish

Not all black finishes are created equal: between PVD, DLC, black rhodium, black polish, and ultra-absorbent coatings, there are substantial differences in process, hardness, and purpose that change everything, both on the workbench and under the loupe.

PVD (Physical Vapor Deposition) is the most widespread. It deposits an extremely thin layer of material onto steel in a vacuum chamber. It costs less than DLC and is sufficiently hard for daily use, but remains susceptible to deep scratches. DLC (Diamond-Like Carbon) is harder: the amorphous carbon created by the plasma process forms a surface that approaches diamond hardness. I often use it as a reference point when a client brings me a PVD-coated case with scratches in the workshop—I show them the difference by touch before I even start working on it.

Black polish—or polissage noir—is something else entirely. It's not a coating: it's a hand-finished technique brought to absolute mirror polish on the flat surfaces of movement components. Bevels, plate and bridge surfaces, sometimes the flanks of wheels. Pietari Kupias combines it with snailing and perlage on his Katedraali; A. Lange & Söhne practices it on the internal junctions of plates. The visual result—that surface that appears black because it absorbs reflected light in all directions—depends on the perfect geometry of the plane and not on any pigment.

On the ultra-absorbent coating front, Musou Black (99.4% absorption) and derivative materials used by manufacturers like Venezianico and CIGA Design stand opposite to black polish: instead of reflecting in a controlled manner, they eliminate nearly all reflection. The effect is one of bottomless visual depth. The original nanotubular Vantablack exceeds 99.96% but is fragile and not approved for contact surfaces: in watchmaking applications, Musou Black or similar variants are preferred.

Black rhodium is an electroplated coating with darkened rhodium alloys. I see it often on indices—Angelus uses it in contrast on bronze dials—and on Laurent Ferrier bridges. It resists oxidation well, but the coating is thin: on high-friction surfaces it degrades before DLC or PVD.

Fully pigmented black ceramic—where the pigment is integrated throughout the entire sintered mass, not just on the surface—ensures that a deep scratch won't reveal a different color underneath. Hublot was among the first to industrialize it in 2006. The technical limitation remains brittleness under torsion: ceramic is hard but not ductile.

A case unto itself is Zeitwinkel's Black Or: a dark treatment applied to German Silver plates that darkens the natural golden tone without erasing the finishes underneath—Côtes de Genève, perlage, bevels remain legible. The contrast play with the gilt wheels and rotor is deliberate and works well as a tool for reading the movement.