Silicon hairspring

A silicon hairspring is a balance spring produced from a silicon wafer rather than drawn and coiled from a metal alloy. The published European patent application EP 3 056 948 A1, Silicon hairspring, in the name of Master Dynamic Limited of Hong Kong, was filed on 12 February 2016 and published on 17 August 2016. Its first claim covers a spring whose "core formed from mono-crystalline silicon wafer oriented along the crystallographic axis <110>" carries "at least one peripheral coating of a material having a thermal elastic constant different from that of the core," the coating being how such a spring is made to compensate for temperature.

The application's own statement of what silicon offers over metal is that the material "does not creep and oxidize over time in comparison with most metal alloys", that it is "entirely non-magnetic", and that temperature sensitivity may be "minimized or substantially eliminated for normal operating parameters". These are assertions made in a patent application, a primary record of what was claimed, and when, not a measurement.

Omega markets its own silicon balance spring as the Si14, stating that "In 2008, OMEGA released the Si14 balance spring, created to resist the ever-increasing magnetic forces that are part of our lives", that it is "Named after the chemical symbol and atomic number of silicon", and that watches with its Co-Axial movement fitted with the Si14 "are delivered with a full four-year warranty". Those are Omega's own claims about its own product.

What is not established here: independent certification of the material itself. The Federation of the Swiss Watch Industry's published list of available NIHS norms contains no entry for silicium, and no standards body was found in this session that defines or tests a silicon balance spring as such. The claims quoted above stand as the applicant's and the brand's own words, not as figures from a neutral testing body.