One of the smallest, most important, and most mysterious components of a watch movement. So complex that only handful of companies actually manufacture them and that even within those companies the process remains a secret. Hairsprings are not only very intriguing watch components but also a sign of very high quality, if produced in-house.
Hairsprings are incredibly thin (0.03 mm), flat spirals, that along with the balance wheel, exist to regulate mechanical watch movements. They are responsible for restoring force to the balance wheel, restoring force being the force that brings a physical system back to equilibrium – essentially, it balances the balance wheel. They are manufactured specifically to be temperature resistant and impervious to outside shocks, while beating an incredible 1.4 million times a day!
The hairspring, along with the balance wheel, was invented in 1675 by Christen Huygens, a famous Dutch mathematician, astronomer, and inventor. Since this invention, the regulating system for watches has not changed significantly, hairsprings in particular, have mostly changed in terms of the materials in which they are produced. They were originally produced in gold or steel, until the 20th century, when technology allowed for different alloys to be used in their place. Rolex uses Parachrom, a proprietary blued alloy made of niobium and zirconium that is anti-magnetic and temperature resistant.
To this day there are few brands that manufacture their own hairsprings, Bovet and Parmigani Fleurier are two prominent examples. Their processes are both shrouded in obscurity, most likely due to competition. Nonetheless hairsprings remain one of, if not the most critical component of modern mechanical watch movements, and an important piece to take note of for any budding watch collector.
Bovet Récital 22 Grand Récital, priced at $470 000 / Credit: Forbes