Resistance

In watchmaking, resistance is not a single property: it is a family of distinct technical requirements that a watch must meet to function in real-world conditions. Confusing them is a common mistake, even among those who have been buying watches for years.

Water resistance is the most well-known, but also the most misunderstood. It is expressed in atmospheres (atm) or bar: 1 atm corresponds to approximately 10 meters of static depth. The military Benrus Type I reached 36.5 atm, equivalent to 365 meters. There are dedicated certification standards: ISO 6425 for divers, the German DIN 8310 used by brands like Sinn for their professional diving watches such as the EZM 3 S. A screw-down crown, like the standard one in IWC Pilot's Watches, directly contributes to this seal. Cases filled with silicone or fluorinated oil, an extreme solution adopted by some manufacturers, eliminate reflections underwater and further increase water resistance, but require a thermal compensation system.

Scratch resistance depends on case and bezel material. Steel treated with Sinn's TEGIMENT technology, Rado and IWC's high-tech ceramics, DLC (Diamond-Like Carbon) and PVD coatings, Rolex's Cerachrom, Citizen's Duratect TIC on titanium: these are all different approaches to the same problem. IWC's Ceratanium combines titanium's lightness with ceramic's hardness in a single composite material. Titanium, compared to steel, offers a superior strength-to-weight ratio, which explains its widespread use in sports watchmaking.

Magnetic resistance is today one of the most concrete challenges for mechanical movements, in an era of pervasive magnetic fields. It is measured in gauss: METAS Master Chronometer certification guarantees up to 15,000 gauss. Different design solutions address the same objective: the Nivachron hairspring (non-ferrous alloy), Rolex's blue Parachrom hairspring (nickel-iron paramagnetic alloy), non-magnetic cages that shield the entire movement.

Shock resistance has a longer history. The Incaflex balance wheel, patented in 1927 by the Wyler brothers, was the first structural solution to the problem: an elastic structure that absorbed sudden stresses while protecting the caliber. Today systems like Certina's DS Double Security claim up to 10,000 G of shock resistance. These are technologies born in military or sports contexts, later adopted in the civilian market.

From my bench, I'll say this clearly: a watch can be certified on three of these axes and vulnerable on the fourth. Reading complete specifications, not just the stated depth, makes the difference between an informed purchase and disappointment.