The Balance Spring
This is considered the brain of the mechanical watch, and the place where time is measured. Along with the balance, it is the watch's regulating organ. Its quality determines the watch's accuracy.
The small spring, wound in a spiral (between 12 and 15 turns), is attached by its ends to the balance and the cock. Thanks to its elasticity, the balance-spring enables the balance to oscillate with a resonant frequency. It weighs just 1 mg and is around 0.02 mm thick – finer than a human hair!
The steel balance-spring
The traditional balance-spring is made from a steel wire, drawn and then rolled, and its shape is formed mechanically. It is subject to external disturbances such as knocks, temperature, oxidation and magnetism.
The silicon balance-spring
Silicon is a chemical element (Si 14) abundant on Earth in its oxidised form. It can only be found in its pure form by digging into the Earth's crust. Silicon is the basic element used for electronic chips and computer components.
Following extensive research, and benefiting from the latest advances in technology, the silicon balance-spring was created in the early 2000s. Its manufacture involves a number of extremely specialised industrial operations.
ADVANTAGES OF SILICON
1 - The way in which it is manufactured allows for great freedom of form and excellent geometric precision.
2 - Owing to its physical properties, the silicon balance-spring is insensitive to the effects of magnetism, impacts (everyday knocks) and changes in temperature. Given that there are many sources of magnetism that can affect a watch's accuracy (laptops, mobile phones, magnetic handbag fasteners, medical devices, etc.), the silicon balance-spring offers the customer a clear advantage.
3 - It is scarcely affected by the passage of time, ageing and oxidation.
5-Year Warranty
The unique properties of silicon enhance the accuracy and longevity of a timepiece. Given these technical features, Longines is gradually introducing silicon on all its product lines, and has decided to extend the warranty for all its self-winding watches to five years. The start date is the date of purchase by the end customer shown on the warranty card.