Sapphire
Crystal clear
Sapphire is now one of the most in-demand materials in watchmaking, but a decade ago, Richard Mille was alone in grasping its true potential for use on entire watch cases. The brand invested significant resources in researching and developing new techniques that would elevate its most exclusive calibres in unprecedented ways.
The main benefits of sapphire are its transparency and its radiance, which highlights every detail of the brand’s calibres while subtly capturing the light with cases machined entirely from this material. This timeless, crystalline setting deserved the full attention of engineers and design studios.
It is simultaneously functional, aesthetic and sensory. Its chemical composition gives it an exceptional score of 9 on the Mohs scale of mineral hardness, just behind diamond, which tops the list. Its outstanding properties make it impact- and scratch-resistant, while its soft, tactile surface gives it a warm and comfortable feel on the wrist. This unique material, the product of precise expertise, embodies both preciousness and innovation.
As in the optical and electronics sectors, the watchmaking industry uses synthetic sapphire, which has exactly the same chemical composition, physical properties and crystalline structure as its natural counterpart, but with the added advantage that it can be produced in blocks large enough for creating Richard Mille cases. A sapphire block weighing several dozen kilos is needed to make the three parts of a single curved Richard Mille watch case.
A methodical science
In collaboration with its Swiss partner Stettler AG, the brand uses the Kyropoulos method for the production of synthetic crystal. The material, aluminum oxide, is heated between 2,000 and 2,050°C in a controlled atmosphere. A small sapphire crystal acts as a seed, allowing the synthetic crystal to grow slowly around it. This process can take several weeks of ‘growth’.
The constraints inherent to the use of synthetic sapphire at Richard Mille are unprecedented. Firstly, the complex, curved shapes of its cases have meant that new, particularly demanding machining and finishing processes have had to be introduced. The material’s hardness of 2,000 Vickers and its extreme rigidity during cutting and assembly impose tolerances of just a few microns. In addition, a sapphire case requires more than 1,000 hours of milling and polishing.
When Richard Mille unveiled the RM 056 Tourbillon Split-Seconds Chronograph Sapphire in 2012, it blazed a new trail in watchmaking.
Infinite Horizons of Inspiration
Always ahead of trends, Richard Mille very quickly started to use synthetic sapphire for parts of its movements, such as the baseplate, winding barrel bridge, tourbillon bridge and, a few years later, the central bridge in its RM 56-01 and RM 56-02 models.
More recently, Richard Mille introduced coloured sapphires (blue, green, orange and pink), which require a much more complex manufacturing process than transparent sapphire, as metal oxides must be meticulously incorporated into the crystalline structure. This delicate process makes the sapphire more sensitive to both temperature and growth rate.
In 2015, the brand unveiled its first coloured sapphire creations with the RM 07-02 Automatic Sapphire. These sapphire cases, sometimes set with precious stones, were a world first in watchmaking and perfectly illustrate Richard Mille’s relentless quest to push back boundaries, innovate constantly, and reinvent the aesthetics of modern watchmaking.