Silicon hairspring

A silicon hairspring is a balance spring made of silicon rather than a metal alloy. The hairspring is the tiny spring that makes the balance oscillate at a regular rhythm: it is the component that determines a mechanical watch's accuracy.

What silicon changes

Silicon has three advantages. It is non-magnetic, whereas a metal hairspring exposed to a magnet can stick to itself and make the watch run badly fast; it is the modern answer to magnetism. It is light and does not rust. Finally, it is produced by etching, which allows the hairspring to be given a very precise shape; an oxide layer compensates for the effects of temperature.

Ulysse Nardin led the way with silicon escapement parts on the Freak in 2001. Patek Philippe followed with its Spiromax hairspring in 2006, Omega with the Si14 in 2008, before using it in its Master Chronometer certified calibres. Rolex made a different choice: most of its calibres use a Parachrom hairspring, made of a niobium and zirconium alloy, and the brand has reserved a silicon hairspring, the Syloxi, for certain small calibres since 2014.

Effect on value

On a modern watch, a silicon hairspring is an argument for everyday reliability more than a value driver. It has a drawback: a silicon hairspring cannot be adjusted by hand like a metal one; after a shock it is replaced, generally within the brand's network. On a collectible watch the question does not arise: buyers look for original condition, whatever the material.

Example: the Rolex Milgauss protected its movement with a soft-iron cage; Omega's Master Chronometer calibres obtain their resistance to magnetic fields through the materials themselves, including the silicon hairspring.