Polishing

In watchmaking, polishing is not a single operation: it's a family of techniques that produce opposite optical results, and confusing them is a common mistake even among those who buy and sell for years. The fundamental distinction is between mirrored surfaces — which reflect light directly and uniformly — and satin or brushed surfaces, which diffuse it. The aesthetic value of a well-finished case almost always comes from the contrast between the two.

The most cited technique today is Zaratsu, a Japanese name derived from the Japanese pronunciation of Sallaz, a German brand of flat-disk machines on which it is performed. Grand Seiko uses it systematically on the flat surfaces of bezels and lugs: the wheel rotates at low speed, the operator holds the piece freehand and must maintain the exact angle throughout the pass. The result is a mirror surface with no visible polishing marks and geometrically sharp edges. The same Shizukuishi facility produces Seiko Marinemaster watches with the same processing. On the workbench I've seen original Zaratsu cases next to machine-made refinishes: the difference is immediately apparent from the linearity of the edges, which become slightly rounded after a hasty polish.

At the opposite end is sandblasting, called sandblasting or micro-sandblasting depending on the abrasive particle size. It is obtained by projecting microparticles onto the surface, which loses its specular reflection and acquires an opaque texture that diffuses light. Blasted titanium is particularly common in diving watches because it resists visible scratches better than polished. De Bethune instead uses thermal oxidation of titanium to achieve a blue coloring: it's a heat-driven chemical reaction, not polishing in the strict sense, but worth mentioning because it's often confused with conventional surface finishes.

On movements, finishes have their own names. Geneva stripes — côtes de Genève — are parallel lines obtained with an abrasive tool on plates and bridges. Berçage is hand circular polishing of the flat bottoms of holes. Bevels, the angular chamfers on component edges, are brought to a mirror finish with woods and abrasive powders: slow work, impossible to automate with the same quality. Lapidello is instead the Italian name for the numerically controlled machine used for satin finishing and polishing of cases: useful for serial restoration, but it doesn't replace handwork on a Zaratsu.

A note on vintage watches: the term unpolished in listings is almost always unreliable. Verifying whether a case has truly never been refinished requires direct examination of the original edges and, often, comparison with archive images. Sellers declare unpolished; buyers must verify.