Precious stones in general are entirely at home on watches, and diamonds even more so. While they mainly adorn the bezel, at times the case and often the dial, there is one territory where they struggle to make their luminous presence felt: the movement. Very few brands succeed in accomplishing this particularly complex feat. The first difficulty in setting a stone into metal is that the latter must lend itself to this exercise, meaning it must be malleable. Yet the brass from which most calibres are made is too hard, which is why gem-set movements are in solid gold – jewellers’ favourite material. The second obstacle is that they must be able to withstand an extremely daunting operation: the metal to be set must first be pierced in order to make room for the stone, and then pushed over to hold the gem in place. The setter therefore skilfully lifts up a tiny strip of gold in order to create the claw that will ensure the longevity of the setting.
Whereas there is nothing too insurmountable about this process on a bezel or a ring, a 1mm-thick bridge whose geometry determines the smooth running of a calibre is a whole different matter. Setting a movement without twisting, scratching or scraping the metal calls for sophisticated expertise and meticulous care, even more so than the most refined finishes of traditional Haute Horlogerie. The result is well worth it. Nestling at the heart of a watch with no dial to obstruct the view, watches with gem-set movement sparkle with dazzling radiance, further accentuated by the stones on the bezel – since such adornment is rarely confined to the calibre alone. The effort involved in this endeavour is subtly concealed. These models are complete works of jewellery and watchmaking that often adopt slender or skeleton-work structures designed to match the exquisite delicacy of the craftsmanship involved.
There are several possible ways of achieving a similar result: optical illusions that avoid the need to plunge into the heart of the movement bridges, springs and plates. Corum for example uses the case-back of its Ti-Bridge Tourbillon Pavé. Since this watch has a baguette movement that takes up very little space, there is a huge background area that can be filled with diamonds. Hublot has opted for the dial side. By fitting a gem-set grid immediately above the movement of the MP-06 Haute Joaillerie model, it creates the impression that the calibre itself is set with baguette-cut gems.
Piaget was the first and has been the most prolific brand in the domain of gem-set calibres. On its tourbillons and more recently on a number of ultra-thin models, it is indeed the only one to offer both brilliant-cut and baguette-cut settings – such as on its Altiplano Skeleton models. Baguette setting is the most demanding of them all, since it involves sinking the stone firmly into the metal around its entire circumference, and not just on three or four corners. The luminous effect is accentuated by the use of coloured stones, a typical Piaget choice designed to create contrasts.
The major new Graff launch in 2015, the Diamond MasterGraff Structural Tourbillon Skeleton is a skeleton tourbillon with ‘legs’ slimmer than those of a grasshopper. Its three-dimensional intertwined structure is abundantly set with baguette-cut diamonds. The components are so delicate that the brand had to set them into the raw metal before transforming them into watch components. Yet machining an already gem-set metal rod with a 0.5 mm cross-section is no picnic. The operation requires a rare degree of care, since it is performed by machine tools that are extremely precise but full of oil, shavings… and dangers. The endeavour is certainly well worthwhile: whereas the non gem-set watch already allows a lot of light to filter through, its fully baguette-cut diamond-set version shines as brightly as the spotlights in the watchmaking shows.
Boucheron has long since proven its ability to explore the possibilities afforded by gem-encrusted calibres. In its Haute Joaillerie watches featuring the Tourbillon with Three Gold Bridges calibre* it directly sets the mainplate itself, which is left bare by the specific structure of this Girard-Perregaux mechanism. This approach gives rise to magnificent hawks, swans and peacocks in glistening graded shades of blue and brown, unfurling from their mechanical heart to the tip of their wings.
