Which material did Charlie Edouard Guillaume develop for balance springs?

Charlie Edouard Guillaume developed Invar as a material for balance springs in watches. Invar is an alloy primarily made of iron and nickel, and it is known for its remarkably low coefficient of thermal expansion. This property is particularly crucial in horology because it allows for greater accuracy in timekeeping. Changes in temperature can cause materials to expand or contract, which can lead to inaccuracies in time measurement. By utilizing Invar for balance springs, watches can maintain their precision across a range of temperatures.

Other materials, such as gold, silicon, and steel, are also used in the watchmaking industry, but they do not possess the same low thermal expansion properties as Invar. Gold is often used for its aesthetic value and resistance to tarnishing, silicon is favored for modern technological innovations, and while steel is a common material in various watch components due to its strength and resilience, it lacks the specific thermal characteristics that make Invar particularly suitable for balance springs. Thus, Invar's unique properties solidify its importance in the development of precise watch mechanisms.