Brass is a copper alloy with approximately 30 to 40 percent zinc.

Brass started to be widely used to produce watchmaking components in the 17th century. Prior to that, they were made from iron and steel.

Being resistant to corrosion, brass became an affordable alternative to iron. It was also relatively inexpensive, readily available, malleable, and easily shaped and engraved. These characteristics made it ideal for producing watch components, such as mainplate, wheels, barrels, and bridges.

During the 18th and 19th centuries, the industrial revolution brought advancements in manufacturing processes, including the mass production of watches in the second part of the 19th century. Brass played a crucial role, as it facilitated the production of components on a larger scale. The introduction of machine tools and automated processes enabled more precise and efficient production, further popularizing the use of brass in watchmaking.

Nowadays, brass stays a widely used metal for watch components and is appreciated by many artisanal watchmakers.

You can recognize the “historical” brass that was once used in pendulum work because it was slightly green. Modern brass has lead in its alloy to make the chip more brittle and facilitate machining. The addition of this lead makes the brass browner.

This metal is mainly used for the largest components of the movement such as plates and bridges but also for the wheels of the gear train because the friction of this metal goes particularly well with the polished steel of the pinions.

The main advantage of brass is that it is easy to machine and wears little on cutting tools. Also, it oxidizes but its oxidation remains a surface oxidation that can be considered as a self-protective layer. Unlike steel, this oxidation does not go deep and can be easily removed with a quick polish.

It is a relatively soft metal which limits its use for smaller components.