This question was prompted by the new Tourbillon RM56-02 Sapphire by Richard Mille, and also by one of those ironic paradoxes floating around the Internet. If the black box on an aircraft is indestructible, why don’t they make the whole aircraft from that material? In watches, sapphire glass is used for the watch glass and the transparent caseback, offering a look into the movement. In some pieces, there are windows in the caseband, particularly if the watch has a tourbillon or another detail that merits all-round appreciation. Some watchmakers such as Christophe Claret use sapphire for the bridges, extending the transparency down into the movement. So why not make the whole watch case out of sapphire glass?
The answer is, it’s so hard and resistant that it would take an exorbitant amount of machining. Sapphire glass, which would more correctly be called synthetic sapphire, is crystalline aluminium oxide, or corundum. Chemically it’s exactly the same as sapphire gemstones, whose blue or other colours are the result of impurities. The principal characteristic of sapphire is its transparency, and its hardness. On the Mohs hardness scale, it is at 9, just behind diamond at 10, and moissanite (siliicon carbide, often used as synthetic diamond) at 9.25. This makes it amazingly scratch-resistant, and so ideal for watchglasses and casebacks.
The Tourbillon RM56-02 Sapphire by Richard Mille, whose presentation coincides with the Watches & Wonders exhibition in Hong Kong (30 September – 2 October 2014), is a limited-edition watch – just ten – with a case in three parts, shaped for ergonomic comfort, all ground from solid blocks of sapphire. Each case requires 40 days of continuous machining. All the movement bridges are in sapphire as well, for another 400 hours’ machining: we’re talking about circa 1,500 hours machining time for a single watch. The movement is suspended inside the case using a system of braided metal cable, 0.35 mm in diameter, and pulleys, four attached to the case with another six on the titanium base plate. The cable tension can be adjusted by means of a ratchet at 9 o’clock, and it is displayed by an indicator at the 12 o’clock position. The complexity of production means that the watch has a high price tag: the RM 56-02 costs $2,020,000.
The RM 56-02 builds on Richard Mille’s previous experiences in transparency, with the RM 056 Sapphire Tourbillon Split Seconds Chronograph (2011) which had a complex case in sapphire, and then the RM 56-01, with baseplate, bridges and third wheel also in sapphire. The cable-suspended movement was first seen in the RM 27-01 Rafael Nadal. The RM 56-02 combines the two, adding more sapphire components, namely the winding barrel bridge, tourbillon bridge and centre bridge. The strap is partially translucent, made in Aerospace Nano® by Biwi SA, a company operating at Glovelier in Switzerland; Aerospace Nano is a synthetic polymer in which nano-reinforcements create great strength in a material that is also elastic, waterproof, silky to the touch and very comfortable.
I look forward to seeing it in operation somewhere. It looks like a unique look into a watch movement, with tourbillon at 6 o’clock, and skeletonized hour and minute hands. But I won’t be going to Hong Kong for Watches & Wonders, you know, it’s a long flight, and while Richard Mille has done the impossible and made the whole watch out of sapphire, planes are still made out of various lightweight alloys, with just the black box indestructible…