Transparent watch cases: seeing is believing

Watch casemaking has crossed the Rubicon: the mechanical ballet of movements can now be seen through cases that are completely transparent. Nick Foulkes reports

Richard Mille sapphire crystal RM 56-02 on rubber strap, about £1.33m
Richard Mille sapphire crystal RM 56-02 on rubber strap, about £1.33m

Some time ago I wrote about the return to popularity of the skeleton movement. Traditionally, skeletonising involved a watchmaker working patiently with a saw and file to remove as much of the metal from the movement as possible without compromising its ability to function. It is a thing of beauty, but with new aesthetics, new materials and new ways of making components, the culture of the skeleton watch has changed. It is no longer “just” a matter of trimming and piercing an existing movement: makers are creating movements conceived expressly as skeletons, or perhaps it is more accurate to say they are designing movements that maximise the impact of transparency. Negative space has long been used in art, and now it is increasingly appreciated in watchmaking.

Zenith white gold and sapphire crystal Pilot Type 20 on alligator strap, £150,300
Zenith white gold and sapphire crystal Pilot Type 20 on alligator strap, £150,300

And as movements become ever more valued as works of kinetic sculpture in miniature, so the watch case has evolved to allow the wearer to see more of the mechanical ballet of interacting components. First there was the crystal caseback, next the dial was pierced to allow inspection of such marvels as the tourbillon, then the dial was dispensed with altogether, and now even the case walls are acquiring windows to give a transverse view of the mechanics.

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Of course, the side view is not necessarily the most exciting and you may have to squint a bit, but sometimes a completely unobstructed view from either side has advantages, as with Corum’s long, thin, in-line Golden Bridge movement, where the winding crown is tucked between the lugs at six o’clock. Indeed, when a movement has an especially unusual architecture, it is natural that the creator wants to show it to best advantage, as was the case when Chopard co-president Karl-Friedrich Scheufele relaunched the venerable Ferdinand Berthoud marque in 2015. Berthoud was an 18th-century maker of marine chronometers characterised by a unique pillared construction that Scheufele wanted to recreate within the confines of a wristwatch. Considering that this is a watch of 1,120 components, the pillars give a surprisingly airy feel to the movement, best appreciated through the crystal side panels of the octagonal case.

Rebellion Timepieces sapphire crystal Magnum 540 Grand Tourbillon on silicone strap, £1.56m
Rebellion Timepieces sapphire crystal Magnum 540 Grand Tourbillon on silicone strap, £1.56m

Today, casemaking has crossed something of a Rubicon; materials and machining techniques have advanced to a degree that permit the manufacture of cases that are completely transparent. It is somehow fitting that one of the first brands to experiment with a fully transparent case was Cartier, when it showcased its concept watch ID Two in 2012. Transparency has been something of a Cartier signature for a century or so, ever since it introduced its mystery clocks, the hands of which, sandwiched between two planes of crystal, seem to float in space and move unaided. However, for the ID Two, it was not crystal that was used, but ceramic.

Front of Hublot sapphire crystal LaFerrari, £397,000
Front of Hublot sapphire crystal LaFerrari, £397,000

“Ceramic is usually opaque,” says Cartier’s head of watchmaking Carole Forestier-Kasapi, “and we worked for three years to develop the first totally transparent ceramic.” The process is protected by a patent and, understandably, Forestier-Kasapi is reluctant to give too much away, revealing only that it is a matter of heating and moulding the material. “Normally for an opaque ceramic you do just one mould, but this process requires several steps.” Cartier has no plans to put the transparent ID into production just yet, but there are potential uses for the technique within Cartier’s existing watches, in particular those that have to use hand-shaped mineral glass instead of the significantly more robust sapphire crystal because of their shape.

Side of Hublot sapphire crystal LaFerrari, £397,000
Side of Hublot sapphire crystal LaFerrari, £397,000

Watch glass is also an issue for Richard Mille. But although he describes the production of his outer and inner glass surfaces as a nightmare (not least because both are curved to fit on the wrist, and changes in curvature require the tooling to be reset numerous times, increasing the potential for breakage), he took it upon himself to produce a watch entirely of crystal (about £1.33m). Mille is not a man usually given to understatement, but he might be guilty of it on this occasion when he describes the process as one of “extreme complexity”. He continues, “There are so many different radii… which is why many subcontractors couldn’t do it.”

Cartier “Ceramyst” ceramic ID Two concept watch
Cartier “Ceramyst” ceramic ID Two concept watch | Image: Joël von Allmen, © Cartier

Just how complicated becomes apparent when he says it takes 1,000 hours to prepare the case, cutting the parts from a solid block of sapphire crystal, then polishing them. A further 430 hours are spent on machining and finishing the movement bridges, which are also in sapphire crystal. And all this is before work starts on assembling the watch, which, with its unusual microscopic braided-steel suspension cables at each corner of the baseplate (giving it the look of a trampoline), can be described literally and figuratively as a true horological high-wire act in itself.

H Moser & Cie sapphire crystal Venturer Tourbillon Dual Time on rubber strap, about £706,000
H Moser & Cie sapphire crystal Venturer Tourbillon Dual Time on rubber strap, about £706,000

It does indeed sound like a nightmare to make, but Mille insists: “It was my dream. I’ve always been into seeing mechanics. When I was young, going to air and car shows, very often you had transparent bonnets, and sometimes you could buy model aircraft or cars that were half transparent.” Making the dream a reality has come with a hefty price tag of SFr1.89m (about £1.33m), and only 10 will be made.

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So far, that has tended to be the pattern of crystal-cased watches: very small production, very high prices, and coming from niche independent makers. As well as Mille, H Moser & Cie from Schaffhausen made a one-off crystal-cased tourbillon with a price of about £706,000, and the Geneva-based maker Rebellion Timepieces asks £1.56m for its Magnum 540 Grand Tourbillon.

But there are signs now that the crystal case is moving out of the niche. Zenith is not a recondite independent brand, but a long-established maker famous for its El Primero automatic chronograph and now part of the LVMH group. It was looking for a way to showcase the mammoth 5011 K movement that is at the heart of its 60mm pilot’s watch recalling the historic connection between Zenith and Louis Blériot, and which is decorated with engravings telling the story of the French aviator’s flight across the Channel. “It is one of the legendary movements for Zenith and we thought that collectors would like to see as much of this movement as possible,” says Zenith CEO Aldo Magada.

The effect is impressive, and because the crystal case is not as complex as the Mille, the manufacturing process was not as costly and the price is comparatively attractive at £150,300. “The only concessions we made were to have a small metal bezel on the front and not to have screws directly in the sapphire, but to have a fine metal column on the six points of the bezel. Putting screws into sapphire is more difficult, and in the long term questionable, because it could weaken the sapphire, making it more susceptible to shocks.”

Hublot’s excursion into transparent watchmaking is a by-product of the brand’s experience with highly resistant materials at its research and manufacturing facility in Nyon, outside Geneva. The creation of its super-hard “Magic Gold” called for special new machines and then lasers for cutting it – both now used for ceramic and sapphire. “Sapphire is similar to ceramic in resistance and hardness,” says chairman Jean-Claude Biver, “which means we can use exactly the same methods, the same tools, even the same people. The big difference is that sapphire needs to be polished like a diamond. That is the difficulty and accounts for the price, because polishing, depending on the complexity of the watch case, might break anything up to 50 per cent of the pieces.”

Hublot offers two of its movements in sapphire crystal cases, the cobra-headed 50-day power reserve (LaFerrari, £397,000), arguably the brand’s most exotic and sculptural movement, and its Unico chronograph. The latter is a less extravagant mechanism, but is a more significant watch in that by the standards of crystal cases it is virtually given away at around £40,000. Biver estimates that this year Hublot will make 1,000 to 1,500 crystal-cased watches. He is also offering transparency in a variety of colours. As well as clear, there is a smoky crystal, a blue crystal planned by the end of the year and other colours in the pipeline. But Biver’s interest now is to get to work on the movement, and make as many of the components as transparent as possible. “I would love total transparency,” he says with his trademark enthusiasm. “I would love a watch where only the wheels are opaque.”

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