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The Richard Mille Sapphire Marvels

Editor's Picks

The Richard Mille Sapphire Marvels


Richard Mille’s crystal cased watch series was initially introduced at SIHH 2012 with the RM 056. An apparition of a watch as it stood in the case on the Richard Mille stand; it appeared to levitate in the display case. Richard’s RM 056 was a ghost of a machine. Universally applauded and lauded, it was both an aesthetic and technical feat of horology. How, with a complex three-part structure, could the case be made from crystal, second only to diamond in hardness, and with so many intricate surfaces and shapes? Not least of which, the curvature of the case in three parts to match together perfectly.
Seeing the crystal case manufacture and the case in abstract (with no movement inside) I was reminded of the way Yves Mathys (R&D and Production Director at Richard Mille Watches SA) described the first time he met Richard Mille. It was a warm summer’s day and Dominique Guernat was bringing Mille to meet Mathys and describe a new project. His quote from that first meeting aptly describes how different the Richard Mille watch design was: “He showed me this watch [the RM001 prototype] and I thought– it’s an extraterrestrial!! We have an extraterrestrial ship for a watch!” But he could see how Mille was onto something different for the industry; something new and innovative. That vision was enhanced further with the case made from sapphire crystal.

In the years since, Mathys has held the helm for developing and producing Richard Mille watches. He initially spoke to Mille about the idea of producing a complete top section for the case made of crystal about four years ago.

But in discussion with Mille, that was changed to: “Why not the whole case?!” A mock-up in Perspex was put together, and once all agreed, the project began to take shape. The first step to consider: “Is there anyone else out there crazy enough to give this a try!?”


To undertake the project, Mille turned to Switzerland’s (and possibly the world’s) foremost crystal firm: “Stettler Sapphire”. A privately-held, family-run firm, it is the typical example of a Swiss specialisation. Stettler produces the sapphire crystals for a number of high-end watch firms; certainly a few from the Richemont Group, from the LVMH group, and other larger and smaller independents who require complex crystal shapes for their watches. Mille had used Stettler for the crystal dials on his watches already, so he knew of their premier status and quality in the market.

Founded in 1881, the company initially produced jewels for watch movements, but in the late 1920s Stettler moved over to sapphire crystal production. There are two centres of production. The factory in Switzerland deals with the research and development, and the production of complex orders. The factory in Mauritius deals with the regular production sapphire crystals that are generally machine-produced. Stettler’s position in the industry is such that most of us wear a watch with a Stettler sapphire crystal covering the dial.

A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The atomic structure makes sapphire crystal similar to and second only to diamond in terms of hardness. It makes the crystal resistant to any change in shape, but by the same token, it is very difficult to machine into a complex shape. Crystals are grown from an initial seed by a variety of methods. The resulting raw crystal shapes are then used for a number of different purposes. The smaller, round, crystals (produced by – for example – the Stepanov method) are cut to into discs, shaped to be perfectly round, and then polished on machines that revolve the discs against a paste. Get enough cutting machines, and enough polishing discs, and you can produce about 60,000 round flat watch crystals in a year for any one set of machines.

Crystals for more complex shapes are grown by the Kyropoulos method which allows the growth of large sapphire crystals with a first- or second-grade optical quality. It is crystal grown by this method that is used in the Richard Mille RM 056 case. A step in complexity above that are curved surface crystals for various watch brands, as well as the crystal that was developed for the RM 053-01. Other watch brands have attempted crystal watch cases, but generally, the case has been round, with flat surfaces, and without any complexity inside the case that is required to hold the movement. If the requirement is that the case is flat on the surfaces, the machining and polishing of the crystals is a reasonably straightforward task. Not easy, but within the bounds of what was known about machining more complicated shapes with crystal on a small scale.

The Complexities of the Crystal RM 056 Case Shape

What is different about the Richard Mille watch case is the three-part structure, where the three parts have to fit to within an allowance of 1/100 of a millimetre. The RM 056 is after all, a fully functioning Richard Mille case with a water resistant rating of 30 metres. It is one of the most complex case shapes to manufacture – even when the case is made out of known materials – as the tolerances are such that specialised measuring equipment is employed to ensure accuracy.

The upper and lower parts of the case are both curved and non-monotonic. In other words, the curvature is not a constant over the surface: shallow at one part, slightly steeper in another. With an exact CNC machine, such curved surfaces can be achieved within the necessary tolerances. For crystal, it is a whole new game. Chief among the problems is that while you can cut the general shapes for the crystal parts for the case, it is the finishing and polishing where the problems really start. The real problem is that the polishing cannot be seen! Submerged within a pot of viscous sand, the polishing takes place in an area where no measurement can be taken. To polish the surfaces to the standard required, the piece has to be removed from the polishing machine and periodic measurements made. Anything not within the 1/100th of a millimetre tolerance (at all points of contact between the case parts), the part is rejected and the process starts all over again.
Further problems arise with the drilling of the holes for the screws, pushers and crown. At any one moment the drilling can cause the crystal to crack or shatter and all the work thus far is lost. The whole process seems to just be waiting for a disaster to happen! The middle part of the Richard Mille case is intricate and contains a number of ridges where the movement is screwed into the case. All ridges and surfaces have to be polished to an exacting standard, there is nowhere to hide in a clear crystal case!

Cresting Hurdles

One way to give the ‘cost’ of the research and development for the RM 056 some perspective, is to consider what else could have been achieved with the same resources (an opportunity cost) committed towards fabricating the case. Think of it this way, instead of producing the five Richard Mille RM 056 cases in each iteration (the RM 056, RM 056-01, and the RM 056-02), Stettler could have produced approximately 60,000 curved watch crystals in the year. The annual production for the whole factory would be about 120,000. In other words, five RM 056 cases represented half of Stettler’s annual production. Five RM 056 cases took a year to produce; or about two and a half months each. Just the necessary outlay on the new ultrasonic cutting machine was approximately the entire year’s revenue on normal spherical sapphire crystals.

The work also required considerable investment by Stettler (underwritten by Mille’s order). Without the advent of the new ultrasound polishing and cutting machines, all of which had to be acquired for the new work, the project would not have been possible. The RM 056 case is at the outer limit of what is known and possible with cutting and polishing sapphire crystal.  The project had been in development for just over three years, once Mille signed up to the idea.

A Trail of “Bleeding Edge” Innovation

Once Mille had developed the technology he was able to push forward and develop more complex sapphire crystal watches: the RM 056-01, RM 056-02 and the RM 053-01. What started out as research and development for just a single watch case turned out to be basis for a series of watches and a watch that can withstand the most brutal of impacts on the crystal itself.

The RM 056 series has stood out as the forefront of sapphire crystal research. The RM 056-01 went one step further and had bridges, at times wafer thin, cut and polished from crystal. Likewise, the RM 056-02 was a masterpiece of crystal case complexity. For the RM 056-02 Richard employed the same tension cable system as he had with the RM027-01; but the effect of cutting and then polishing a complete sapphire crystal case with the necessary interior elements to support the tension cable resulted in a sapphire crystal case that had a higher degree of complexity hitherto not seen before – or since, for that matter.
The crystal watch is absurd on one level! Why would you want to produce a watch case that could shatter? You do not have to worry about hairline scratches on the case, but if you knock the case on a hard or sharp object with sufficient force, you could see the sapphire case crack or even shatter in front of you. But the RM 056 series are opus watches and fulfil the governing philosophy that it is not the material that should be seen as the value element in the watch, but the techniques and work invested to develop that material to the finished watch. That’s Richard Mille! It has always been his philosophy to attempt the new, the seemingly impossible, and to complete it. Not to count the cost, but to show what can be done; to go with the commitment and enthusiasm for the new, and the resolve to see it through to the end.

The RM 056 series and the research into sapphire crystals has spawned a series of crystal watches by other watch firms. Richard Mille might not have been the first: but the other watches were simple round cases with standard movements. What Mille did was something completely different and because of that, he was the precursor to the current spate of crystal case watches on the market. The casework and design entailed both the vision to see it, see it through, and the research and technical achievements to realise that vision. It becomes a lot easier to see a solution once someone else has demonstrated that it can be done. The racing machine on your wrist continues to lead the rest of the field.