arbon is a material that Greubel Forsey has studied for many years. Giving it complex, architectural shapes, all with the highest level of watchmaking finishes, is an exercise that requires patience and technical mastery. Now, the conditions are ripe to give life to the new Balancier Convexe S², one of the Atelier’s iconic creations.

The new diameter of 41.5 mm has been specifically designed for carbon. It’s a radical change, immediately visible on the wrist. This timepiece is tighter, livelier, and even more modern. The very dark tone of the carbon reinforces the feeling of a very compact piece, while staying open to display the movement, complication and finishes.

From a technical perspective, the challenge was significant. To impose as complex a geometry on carbon as that of the Balancier Convexe S² convexe case is an unprecedented move in watchmaking. It requires a precise combination of temperature and pressure. Heat makes the carbon more flexible to work with; pressure gives it its shape. A conventional case usually requires two tonnes of pressure per square centimetre. For Greubel Forsey’s signature convexe case, it was necessary to apply 16 tonnes: 8 times more than is conventional.

By multiplying the layers of carbon, each of which measures 1 to 5 microns, Greubel Forsey has obtained a much denser carbon case, revealing the perfect combination of technique and aesthetics so well known to the Atelier manufacture.

Each case is individually enhanced by the arrangement of its fibres, carefully controlled by Greubel Forsey to create the perfect profile. The direction of the carbon fibres is a top priority, so that they align with the curvature of the convexe case, which is underlined by the hand finishing.

Convexe on the case back as well as the display side, the timepiece hugs the wrist perfectly. At 12 and 6 o’clock, the two converging lines give the Balancier Convexe S² a 3D geometry of unequalled complexity. It delivers an unprecedented volume, giving way to a vast open space under the sapphire crystal at 6 o’clock. Within, the 30° Inclined Balance Wheel that has been completely redesigned to fit the new proportions of the carbon case, has plenty of space.

As always with Greubel Forsey, finishing is a crucial stage in developing a timepiece. For its carbon version, the new Balancier Convexe S² has stuck to traditional finishes for the case, lugs and crown. The bezel and lugs alternate between matt and grained finishes.

The crown asserts a bold matt finish. The engraving is of note: always in relief for the convexe case, and remaining so on this carbon case – with particular attention accorded to the precision of the “GF” initials, finishing flush with the centre of the crown.

Between 3 and 4 o’clock is the double openworked “arched” bridge. Its train of wheels below seems somehow suspended as if in a void. With its patent filed in 2019, the bridge has also become one of Greubel Forsey’s aesthetic signatures. It embodies a very powerful, creative vision of fine watchmaking, along with an extremely high level of finish on the titanium components (which are notoriously difficult to polish), with multiple sharp internal angles.

The 303-part movement delivering a 72-hour chronometric power reserve has a perfectly defined architecture, with three large hand-decorated bridges on the movement side. The grained bridges and main plate are perfectly harmonised with the carbon case. The cover of the twin barrels now features a black treatment in keeping with the case and carbon plate. Finally, the relief engraving on the 3D barrel cover blends seamlessly into the redesigned case.

The new Balancier Convexe S² will be produced in two limited editions of 22 pieces each, the small seconds with blue or black treatment, matching textured rubber strap, and a titanium and carbon buckle.

TECHNICAL SPECIFICATIONS

Hours and minutes • small seconds • power-reserve • 30° inclined Greubel Forsey balance wheel system

Movement

Hand-wound movement
• Patents pending
Movement dimensions
• Overall diameter: 37.00 mm
• Thickness: 10.05 mm
Number of parts
• Movement: 303 parts
• Escapement platform: 68 parts
Number of jewels
• 43
• Olived-domed jewels in gold chatons
Chronometric power reserve
• 72 hours
Barrels
• Two coaxial series-coupled fast-rotating barrels (1 turn in 3.2 hours), one of which is equipped with a slipping spring to avoid excess tension
• Relief-engraved text, circular-grained, black treatment
Balance wheel
• In-house variable-inertia with 6 gold mean-time screws (12.60 mm diameter)
Frequency
• 21’600 vibrations/hour
Balance spring
• Phillips terminal curve
• Geneva-style stud
Bridges and main plates
• Carbon and titanium
• Frosted, polished bevelling and countersinks, black treatment
• Multi-level, openworked suspended-arch bridge, black treatment, straight-grained and polished, polished bevelling and countersinks
Movement side
• Frosted bridges, polished edges and bevelling
• Gold plate with engraved limitation number, circular-grained, polished bevelling and countersinks, straight-grained flanks
Escapement platform
• Titanium
• Inclined at a 30° angle