- Tradition - Tradition Tourbillon Fusée 7047

The balance spring is one of a series of vital parts at the heart of the movement. Its regular oscillations give the movement its rhythm and regulate the flow of time. Crucial to the workings of a mechanical watch movement, the balance spring is also the most responsive in terms of improvements to timekeeping precision.

The balance spring is a very fine coil spring. Usually made of metal, it is vulnerable to shocks, magnetic fields and even the pull of gravity, which can cause warping. Made and marketed by Nivarox-FAR, a Swatch Group enterprise, the alloy traditionally utilised to make balance springs is designed to increase its rigidity as its temperature increases, offsetting in this way the balance's increased inertia stemming from the latter's heat expansion.

Long viewed as one of the key components of movement precision, the balance spring has benefited from a lot of research and experimentation, with Breguet leading the way.

In 1795, Breguet conceived the “Breget overcoil” spring, today still the reference in terms of balance springs, the choice of the finest watch houses and craft watchmakers. A.-L. Breguet got the idea of altering the balance spring's terminal curve by raising its end and bending it slightly as a way of improving its isochronism. Another Breguet, Louis-Clément, in 1830 sought to prevail over magnetic fields by crafting balance springs in glass instead of metal. Breguet himself had made balance springs in gold to counter oxidation. One such cylindrical spring was fitted in the celebrated Marie-Antoinette watch; its shape was designed to improve considerably its isochronism by repoising its centre of gravity.