Technical Notes: The Silicon Hairspring

What is a Hairspring?

A tightly wound hairspring attached to the balance wheel.

Before we get into the nuances of silicon hairsprings, some of you might want to know what the hell a hairspring, or balance spring, is in the first place. Well, it’s basically part of the “heartbeat” of a mechanical movement. It’s a tightly spiraled spring attached to the balance wheel. Together with the balance wheel, a harmonic oscillator is formed – put simply, a system which experiences a restorative force equal to that of the displacement force. In a vacuum, a harmonic oscillator is perfect and could continue to oscillate forever, but, this is the real world, and things like friction get in the way. With the help of regulation and a supply of power from the mainspring, the hairspring and balance wheel can overcome external forces and run at a precise resonant frequency. If your eyes haven’t glazed over yet, let’s continue.

Quick History on Hairsprings

Conceived by Robert Hooke in the 1670s, the hairspring greatly improved timekeeping capabilities of the pocket watch. It may even be more accurate to say that it made the pocket watch a viable daily accessory. Hairsprings were originally made with non-tempered steel before giving way to tempered, or hardened, steel. This shift added anti-corrosive properties, but the issue of weakening remained.

Enter, Nivarox. A nickel-iron alloy, as well as the name of a company who works with said alloy, Nivarox has become the most widely used material for hairsprings. With anti-magnetic, anti-wear, anti-corrosive, and rustproof properties, it’s no wonder why Nivarox is used for hairsprings.

The Swatch Group purchased Nivarox sometime around 1985 and has since become somewhat of a monopoly in the hairspring business. The vast majority of watchmakers rely on Nivarox springs, but in the last decade or so, some watchmakers have decided to break the Swatch Group ties and develop their own.

Naturally, watchmakers haven’t just stopped with Nivarox. Silicon (or silicium) is the hottest material in hairspring technology. Nivarox (the company, not the material) themselves are even working on developing and improving their silicon hairsprings for Swatch Group brands like Omega and Breguet.

Ulysse Nardin, who was the first to showcase a silicon hairspring, has continued their development, with more recent entries being Patek, Rolex and Damasko. It’s no easy feat; lots of R&D costs are sunk into these types of projects, which is a huge roadblock for many watchmakers.

Damasko’s silicon hairspring

So What’s the Big Deal with Silicon?

We just told you that Nivarox had great properties for hairspring performance, so why the move to silicon? Well, silicon, when machined properly, is basically a complete improvement over Nivarox across the board. Temperature resistance, shock resistance, magnetic field resistance – you name it, silicon is better. The primary downside is the fragility of silicon in the production process, which can hopefully be lessened as processes are improved.

Potentially the most impressive and beneficial quality of silicon is the lack of lubricants needed to keep the parts in running order. Friction can be a real pain in the ass when it comes to watchmaking, and silicon significantly decreases it. Let’s say your whole escapement and balance assembly is made of silicon parts; you can be fairly certain the service interval of your movement will be extended beyond the typical 4-6 years.

With the hairspring more or less serving as a proof-of-concept for silicon watch parts, it looks to potentially be the future. Using the process of deep reactive-ion etching (DRIE), it’s very possible to make just about any watch movement part out of silicon. With all of the inherent benefits, don’t be surprised to see more and more parts being crafted from silicon. And putting cutting-edge properties aside, many watchmakers are looking to silicon simply as a way to rid themselves of Swatch Group reliance. We’re entering potentially a new phase in mechanical watchmaking – one that hopefully leads to greater adoption by the masses, and one we’re excited to see unfold.

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