De Bethune DB28GS Grand Bleu

The DB28GS Grand Bleu is De Bethune’’s first 100% sports watch. Equipped with a new caliber, this technical and elegant diver’s model boasts a water resistance to more than 100 metres; and offers excellent readability including in the darkest depths thanks to ingenious lighting inside the movement and a new photo luminescent blue, a different bezel that rotates this time with the crystal to indicate dive times; a titanium case for a light feel and a rubber strap for convenience; along with a five-day power reserve.

Just 10 years ago, De Bethune began developing timepieces with a more contemporary spirit with the first DB28. Already at that time, De Bethune’s founder and Master Watchmaker, Denis Flageollet, an outdoor sports enthusiast, felt the need to create watches adapted to an active lifestyle. In 2015, the first DB28GS was launched.

Based on the observation that a sports watch must be perfectly readable in any kind of weather and every possible situation, a special lighting system has been developed. To illuminate the watch and the movement from the inside, the slightly bluish white light source is produced by a fully mechanical means that works on the dynamo principle.

The result is as simple as the lighting of a bicycle, fully mechanical with no electronics and no battery. A pusher at 6 o’clock activates a small gear train driven by the twin barrel. This gear train, by means of a miniature dynamo, provides the necessary energy for lighting the watch. A few seconds of light is more than enough to read the time, even in the middle of the night.

To complete this ingenious system, Denis Flageollet, in close concert with James Thompson, researched a new blue photo luminescent material to improve the readability of the hands, indices and timer whilst remaining true to De Bethune’s hallmark colour spectrum.

The main research focus was on developing a material containing crystals capable of two different color emissions: one for daytime, allowing the De Bethune blue to come through for full effect in natural light; and one for nighttime, with the same crystals now glowing with a radiant luminescence, and always remaining faithful to the iconic blue.

The result is unprecedented, and truly unique: A new blue, bright, deep, luminous, of an ardent and elegant tonality that casts the perfect De Bethune blue during the day, and yet radiates the same tone in the dark. This exclusive luminescent material, named Blue Moon, was developed in partnership with the Swedish company Black Badger Advanced Composites (James Thompson) in collaboration with Swiss SuperLuminova™ and is now proprietary to De Bethune.

The rotating bezel made its first appearance in watchmaking in 1952. It serves to enable accurate calculation of immersion time, as well as the transition through various decompression stops. of the different levels. Generally, all the numerals relating to the minutes counter are indicated on the bezel, which tends to create a more crowded visual effect.

For the DB28GS Grand Bleu, these indications appear on the sapphire crystal driven by the bezel. This developed in the workshops of the Manufacture in L’Auberson enables the model to remain elegantly slender and instils a pleasing casual chic aesthetic.

Hand-wound, with central seconds and a five-day power reserve indicated on the dial, this is the 27th calibre entirely developed and manufactured by the Manufacture De Bethune, equipped with a state-of-the-art in-house-made balance wheel.

The presence of the titanium / white gold balance wheel and balance-spring with flat terminal curve ensures an ideal mass / inertia ratio for an optimal frequency of 28,800 vph suitable for wristwatches.

It is endowed with numerous properties – such as optimised efficiency, reliability, regulating quality, thermo-compensation, anti-magnetism – leading to concrete results, since De Bethune has already improved the efficiency of its sprung-balance-escapement ensemble by achieving a 20% increase in power reserve.

The calibre is also equipped with the triple pare chute system. De Bethune was not only the first to design a bridge symmetrical held on both sides and thus serving to maintain the balance wheel perfectly in position, but also added two shock absorbers on either end as well as that of the balance wheel itself.

Finally, the DB28GS Grand Bleu does not escape the special attention devoted to the refined work of hand-crafted finishing performed within the company workshops in L’Auberson, such as blued titanium components, zirconium case middle and Microlight decoration.

Water-resistant to 105 metres (10 ATM), the DB28GS Grand Bleu is no exception to the strict rule of wearer comfort that De Bethune applies to its models in general and particularly to the DB28 collection. This exceptional comfort stems from a combination of the light feel of the titanium case, the softness of its hand-polished finish, the 12 o’clock crown position and above all the presence of the patented system of floating lugs that adapt to wrist size and movements.

For the DB28GS Grand Bleu, the lugs have been completely redesigned in a medium size tailored to the sporting spirit of the watch, featuring the famous cones that are especially prominent in this model and adorned with black zirconium inserts recalling the sides of the case middle.

The model is delivered with two straps: a canvas version and a striated natural rubber iteration with titanium folding clasp, which also contributes to the practical and pleasant wearer comfort of this timepiece.

Technical details

Name: DB28GS Grand Bleu
Reference: DB28GSV2AN

Hours, Minutes, Seconds, Power reserve indication between 9 and 10 o’clock, unidirectional rotating bezel, manual dial lighting

Type: Mechanical hand-wound movement
Adjustment: Winding and setting the time by means of the crown (2 positions), push button at 6 o’clock to activate the lightening
Number of parts: 400
Jewelling: 51 jewels
Diameter: 30 mm
Power reserve: 5 days, ensured by a self-regulating twin barrel – De Bethune Innovation (2004)
Specificities: Titanium/white gold balance wheel with white gold inserts, optimised for temperature differences and air penetration – De Bethune Patent (2016)
“De Bethune” balance-spring with flat terminal curve – De Bethune Patent (2006)
Silicon escape wheel
Triple pare-chute shock-absorbing system – De Bethune Innovation (2005)
Dial lighting produced by an entirely mechanical means working on the dynamo principle powered by a twin barrel and manually controlled via a pusher – De Bethune Innovation (2019)
Frequency: 28,800 vibrations per hour
Adornment: Mirror- polished grade 5 titanium motion-work bridge
Plate and barrel bridge covers in hand-smoothed grade 5 titanium and adorned with “Microlight engraving” – De Bethune Innovation (2007)
Hand-snailed barrels
Hand-polished and chamfered steel parts

Blued titanium hours and minutes hands with polished steel insert and second blued steel insert, luminescent tip
Polished steel seconds hand with luminescent tip
Power-reserve indicator between 9 and 10 o’clock

Satin-brushed grade 5 titanium minutes dial with cut-out
Arabic numerals
Rotating bezel crystal with metallised minutes ring

Case material: Black zirconium case middle with “Microlight” decoration, brushed and polished grade 5 titanium caseback and bezel
Case diameter: 44 mm
Case thickness: 12.8 mm
Lugs: Floating lugs in brushed grade 5 titanium – De Bethune Patent (2006)
Crystal: In sapphire crystal (1800 Vickers hardness) with double antireflective coating
Case back: Open in brushed grade 5 titanium
Water resistance: 10 ATM

Natural rubber strap + 1 canvas / leather strap
Buckle: Folding clasp in brushed grade 5 titanium

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