Metalli in orologeria

In watchmaking, not all metals are equal, and the choice of material changes the character of a watch far more than one might think by looking only at the case shape. Stainless steel remains the foundation of almost the entire industry, but around it moves a complex system of alloys, rare metals, and working techniques that define the appearance, durability, and production cost of a timepiece.

The combination of two different metals in the same piece has a precise name: two-tone, or bimetal. In most cases it's steel and gold, paired on case and bracelet. Rolex has registered the term Rolesor to indicate exactly this: Oystersteel plus 18k yellow gold in Yellow Rolesor, steel plus rose gold in the Everose version. Patek Philippe instead uses alphanumeric codes: in reference 5520RG the R indicates rose gold, the G indicates white gold, and the two materials coexist on the same case with distinct aesthetic functions.

Among rare metals, tantalum deserves attention. It has the weight of platinum, a grey-blue color that cannot be obtained with any surface treatment, and a hardness that wears polishing tools very quickly. Its sourcing is complicated by geopolitical reasons: the mines are largely located in countries subject to sanctions. Niobium is chemically close to tantalum, equally rare in catalogues, with a light grey reflection and hardness similar to pure titanium.

Artificial aging of the surface is another path. In the case of the Edox SkyDiver aged steel, a layer of platinum group metals — rhodium, palladium — is applied to steel to simulate a patina of use. The aesthetic result is credible; I can see the difference from natural patina immediately under the lens, but it's not certain that it should concern the wearer.

Mokume Gane is a seventeenth-century Japanese technique that stratifies non-ferrous metals — silver, gold, copper — heated to the fusion threshold without melting completely. The block thus obtained is bent, engraved, and worked: the layers emerge on the surface like wood grain. Kees Engelbarts was among the first to use it on dials; Ondřej Berkus applies it to cases combining silver and copper.

In-house foundry work is a real production advantage. Piaget has been working gold in-house for decades: controlling the alloy from the casting stage allows tolerances that an external supplier cannot guarantee in the same way. On the ethical front, the extraction and refining of precious metals — often concentrated in countries with insufficient environmental controls — remain an open problem that the industry addresses with still uneven results.