Automatic bronze watches
Bronze is an alloy almost as old as humanity itself, and it has been used in the manufacture of arms, coins, statues, utensils and…bronze watches. It has been the most innovative alloy in history, giving rise to several civilizations during the so-called Bronze Age. The oldest bronze alloys were found in what we know today as Iran and Iraq, and they date from the fourth century BC.
Bronze is the name given to the metallic alloy of copper (Cu) and tin (Sn). The former is the base metal, while the proportion of tin used varies between 3% and 20%. The characteristics and color of bronze differ depending on the relative proportions of each element. Nowadays, other elements like lead and arsenic are added to the basic bronze alloy formed by copper and tin. This is done in order to improve some of the mechanical, anti-corrosion and lubricating properties of bronze. These alloys take on other commercial names such as cobalt bronze, arsenical bronze or aluminum bronze, an alloy of aluminum and copper. The alloy of copper and zinc is called brass.
In order to make our automatic bronze watches, here at UNITY we use the CuSn8 bronze alloy for our Jules Verne model, and the CuSn12 alloy for our Beagle model. Both alloys are named “marine bronze”, but they differ in the proportion of tin they contain. We’ve opted for this alloy, firstly, because it allows us to machine make the different parts of the watch casing (case body, bezel, case back and lugs or horns) at high speed and with a very high quality finish. Secondly, it’s been chosen for its historical significance as a “pure” bronze composed of copper and tin. The downside is that, as it’s a not a common alloy commercially speaking, it costs more than 316L stainless steel, for example.
On account of its highly rust-resistant nature, for many years bronze has been the favored metal for use in marine environments. The famous “patina” is just a protective layer of copper salts that coat the material and protect it from rusting. It’s this very feature that has polarized tastes with regard to bronze watches…people either love them or hate them.
What’s your opinion?