Cartier

SJX
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Cartier's Mysterious Timepieces

I've been meaning to post this for some time but computer problems delayed it. Here is look at Cartier's historical mysterious timepieces, as well as the new SIHH watches.

Cartier did not invent the mystery timepiece, though the complication is most frequently associated with the Parisian jeweller because of its magnificent mystery clocks of the early 20^th century.

The origins of the mystery clock lie much further back, in the 19^th century, with Jean-Eugene Robert-Houdin. Born Jean-Eugene Robert in 1805 – he took his wife’s last name to become Robert-Houdin – to a watchmaker in Blois, a town in  central France, Robert-Houdin was originally destined to be a watchmaker.

Jean-Eugene Robert-Houdin  

But his career took a very different turn when he set out to acquire a set of books on horology by Ferdinand Berthoud. After purchasing the books, the teenage Robert-Houdin unwrapped the package to discover that the bookseller had mistakenly given him a treatise on magic instead. That serendipitous mistake led Robert-Houdin onto a glorious career as an illusionist, performing even for Queen Victoria, and he is today regarded as one of the most influential magicians of all time. In fact, the even more famous Harry Houdini named himself after Robert-Houdin, in tribute to the latter’s magical influence.

Robert-Houdin, however, never forgot about horology. In 1839 he unveiled his first mystery clock at the Exhibition of French Industry. Made with clear glass discs on which hands, seemingly floating in mid air were mounted, the mystery clock had the movement movement in the base. Robert-Houdin’s invention astonished onlookers and won a bronze medal.

Several decades later in 1913, Cartier unveiled its very first mystery clock, which was sold to banker J. Pierpont Morgan. It was conceived by French horologist Maurice Couet, who was first engaged by Louis Cartier in 1911. Couet eventually became head of the Cartier clockmaking workshop on rue Lafayette in Paris, wo rking alongside Louis Cartier to create some of the most magnificent clocks of the era. 

Model A in rock crystal  

Based on the same principle as Robert-Houdin’s invention, the first type of mystery clock, known as the Model A, had twin, endless screws to drive each of the discs for the hour and minute hands.

Later in 1920 Couet developed a more sophisticated system in which the discs were turned by a single, central axle with a bevel gear that turned the hour disc, and a multiplier gear for the minutes disc. 

Below: Single axle mystery clocks, including the famous Biliken clock at bottom  

A third, more intriguing but less common, form of mystery clock was also made by Cartier. This had only a single hand connected to a gear on the perimeter of the dial. And it had no dial, so the hand just floated in space.

Regardless of the type of mechanism, Cartier mystery clocks were all lavish affairs, made of precious metal and often decorated with semiprecious stone, gems and other exotic materials. Even the entry level (if it can be called that) Model A clocks are made of rock crystal and solid gold. 

Cartier has made only a few dozen mystery clocks since 1911, and now these are incredibly valuable objet d’art. Vintage clocks, even the simplest Model A, sell for six figure, or more, US dollar sums. And Cartier can still make mystery clocks on request today, for similarly astronomical sums.  

So it is from this rich history that Cartier has finally revived the mystery timepiece in 2013 with the Rotonde de Cartier Mysterious Hours and the Rotonde de Cartier Double Mysterious Tourbillon, both part of the Fine Watchmaking collection.

Though Cartier did make a few Santos 100 Mysterieuse limited editions in the mid-2000s, and also mystery pocket watches from time to time, this is the first time that the mystery concept has been applied to timepieces in the regular collection.

Both the new mystery wristwatches operate on a similar principle to the mystery clocks of the past: sapphire discs with teeth on the rim, driven by gears on the perimeter of the dial. The gears and rest of the movement are hidden by the dial, hence the mysterious, floating effect.

But wristwatches require more stringent standards than clocks, because they are worn on the wrist and subject to far more stress. According to Carole Forestier, head of Technical Development at Cartier, durability and shock resistance were two major considerations in the development of the mystery watches. The Rotonde de Cartier Mysterious Hours for instance was tested to survive 500 consecutive impacts as well as a one metre fall onto a hard wood floor, which means it is as durable as a regular mechanical timepiece. So even though they function on a similar idea, the mystery wristwatches are far more sophisticated than their larger cousins.

The simpler of the two is the Rotonde de Cartier Mysterious Hours with the calibre 9981 MC. This works with twin sapphire discs, one each for the hours and minutes, which are both mounted on a central axis to reduce friction and wear on the rim.

Around the rim of each sapphire disc are metal teeth, which are deposited on the sapphire by Deep Reactive-Ion Etching (DRIE), a process commonly used to etch silicon wafers. DRIE results in an exceptionally precise geometry and position of the teeth, as well as reducing the weight of the disc to just 0.56 g; securing the toothed rim with rivets or screws would increase the weight. The DRIE process is done by Mimotec, a Swiss firm best known for its work on silicon parts for watch movements.

Each of the two discs are driven by gears, which are crammed underneath the dial, along with the rest of the movement, all of which is out of sight so all the wearer sees are the twin floating hands and a central axis. And it is worth noting the hands match the colour of the case, rather than being blued steel which is typical for Cartier; according to Carole Forestier, the reason for this was purely aesthetic, in order to achieve a more subtle look.

Because the sapphire disc time display is so large, even the tiniest speck of dust would be obvious to the wearer. Hence the module for the time display is assembled in a laminar flow cabinet, separately from the rest of the movement, to ensure it is entirely dust free.

A staggering 58% of the surface area of the 31.3 mm diameter of the watch dial is comprised of the mysterious time display, making this a feat of concise and compact watchmaking.

The entire movement, made up of 158 parts, is packed into the crescent-shaped area around the sapphire discs, inside a gold case that is a moderate 42 mm wide. Despite the horological gymnastics, the movement still manages a respectable 48 hour power reserve.

In contrast, the Rotonde de Cartier Double Mysterious Tourbillon has conventional hands for the hours and minutes, but they are not really the point. Below the hands sits a mystery tourbillon, seemingly attached to nothing and spinning away in mid air. Nearly half of the dial surface, 16.5 mm of the 35 mm diameter, is taken up by the sapphire disc of the mystery tourbillon.

And it is not just a regular tourbillon, rather it is a double tourbillon – the carriage makes one revolution per minute as with most tourbillons, but it is also mounted on a sapphire disc that is turning once every five minutes. So as the carriage makes it one-minute revolution on its own axis, it is also making a five minute revolution on the sapphire disc.

The reason for the different rates of rotation is energy consumption – if the sapphire disc were to make one revolution a minute like the carriage, the energy required would be 25 times as much.

Though the Double Mysterious Tourbillon much more complex, it works on the same basic concept as the Mysterious Hours. The sapphire disc with the tourbillon carriage has teeth around its rim, driven by gears on the outside. But in this case the ring with the teeth is screwed onto the disc instead of deposited with DRIE. That is to stay within the conservative limits of the Geneva Seal, which this movement qualifies for.

And across from the tourbillon, also screwed onto the rim of the sapphire disc, is a solid gold weight to counterbalance the tourbillon, for stable chronometry in the vertical position as well as better shock resistance. The tourbillon itself is lightweight, with most of its components being titanium, resulting in a total mass of just 1.35 g.

Like the display module of the Mysterious Hours, the mysterious tourbillon module is assembled in a laminar flow cabinet, to keep it lint free. And the tourbillon is similarly tested to survive 500 consecutive impacts and a one metre drop.

With the Double Mysterious Tourbillon, elegant and compact construction are once again demonstrated. The overall movement is a mere 5 mm high, which is just a bit more than the 4.5 mm height of the ordinary flying tourbillon movement from Cartier. The overall case diameter is 45 mm, which is large, but not overwhelming when paired with its relative slimness.

Robert-Houdin’s first mystery clock was truly mysterious, no one could figure out how it worked; it was a magic trick rather than a timekeeper. Now the secrets of the mystery clock have been revealed in great detail. But the mystery timepiece is like a great magic act performed by a great magician – the audience knows it’s mechanics rather than magic, but it is still amazing enough to be worth watching.

- SJX