The De Bethune DB25 Starry Varius Aérolite Tourbillon, With Meteorite Dial
The dial of this masterpiece from De Bethune has been on a billion year journey to your wrist.
Every watch dial tells a story, but some tell longer stories than others. One of the longest stories a dial can tell – probably the longest by a considerable margin – is the story behind meteorite dials, which are made from the earthly remains of fragments of other heavenly bodies which have fallen to earth. Meteorite dials are not exactly widespread in watchmaking – they have a specific appearance and a specific set of skills are necessary to go from a raw lump of half-melted material, to the spare geometry of a finished meteorite dial. But thereby hangs a tale.
The DB25 Starry Varius Aérolite Tourbillon is a deceptively simple looking watch, at least at first glance. The expansive dial represents a star field as seen from Earth, and as is the case with any Starry Varius dial, it can be customized to show the sky above a specific location on a specific date.
The Starry Varius Aérolite Tourbillon is, essentially, a meteorite dial version of the DB25 Starry Varius Tourbillon. The only indication that you might have at first glance that the watch is more than just a simple three handed watch – albeit one with very distinctive and unusual design features – is the seconds hand, which jumps in one second increments, rather than sweeping smoothly around the dial as is the case with most other mechanical watches, as you can see in the opening minute of Tim’s video review.
Turn the watch over, however, and you’ll see that there is, as is often the case with De Bethune, a lot more than meets the eye.
A Magnificent Machine
The movement is De Bethune’s caliber DB2109V4 and it’s a reminder that while De Bethune is often, and rightly, thought of as a design-forward house, it is also as technically forward looking and technically innovative as anything from, say, Richard Mille – one of the very few modern brands, independent or otherwise, which has put decades of time, energy, and genuine passion into re-inventing the vocabulary of traditional movement design and finishing.
The design of the movement is dominated by a few clear, geometric shapes – there are the two staggered mainspring barrels, top and bottom in the image (which provide a four day power reserve) underneath De Bethune’s signature modified delta-shaped bridge. Opposite the crown, there is the tourbillon cage and balance, under its own curved bridge which mirrors the shape of the curve on the delta bridge right next to it. In the center of the movement, underneath its own blued titanium bridge, is the mechanism responsible for the jumping seconds hand – a “deadbeat seconds,” complication. (Deadbeat seconds, as a complication, can be found in the work of several high-end watchmakers, including F. P. Journe).
The saw-toothed gold wheel at the center of the movement is alternately locked and unlocked by the large anchor and its ruby pallets just above it, with the wheel kept under tension by the spiral spring just underneath it (without it, there would not be any tension to hold the deadbeat seconds wheel firmly in place against the ruby pallets; the spring also provides the energy necessary to jump the seconds hand).
The tourbillon is unusual in several respects. For most of the history of the tourbillon, since it was first patented by Breguet in 1801, they have had a one minute period of rotation (which, in the age of open dialed tourbillons post-Quartz Crisis, allowed the tourbillon cage to double as a running seconds hand as well). De Bethune’s tourbillon as seen here, has a 30 second period of rotation, which offers theoretically better chronometric performance, as the amount of time that the balance and balance spring spend in any given position is cut in half, compared to a one minute tourbillon. Essentially this means that the timekeeping components affected by gravity, spend even less time than normal in any of the extreme positions.
The escapement, in the interests of keeping inertial loads as well as friction, as low as possible, is made of silicon and the balance spring is De Bethune’s patented design, with a separate outer coil fixed to the terminal curve that provides the same benefits as a Breguet/Phillips overcoil, but without adding any additional height. The balance itself is in blued titanium, with white gold inertial weights. The period of rotation of the tourbillon isn’t the only high speed element in the movement – beat frequency is 36,000 vph, well above the 28,800 vibrations per hour of a conventional modern high beat watch, and the same as the Zenith El Primero.
The Dial That Fell To Earth
All this, plus the night sky dial, would be exotic enough, but the deal’s really closed by the use of meteorite for the dial, which makes the celestial aspirations of the Starry Varius very tangible.
Meteorite dials have a unique pattern, consisting of intersecting lines formed by the very large mineral crystals in the iron and nickel that make up the body of the meteorite itself. The size of the crystals you get in any cooling metal alloy is determined by a number of factors, but the single most important is the rate at which the metal cools (the Japanese katana, which inspired the dial of a recent Grand Seiko, is characterized by a highly complex crystal structure). If you cool an alloy fast enough, a regularly repeating pattern of crystals doesn’t have time to form, and you get, as oxymoronic as it sounds, a metallic glass, which like the glass in your windows, doesn’t have a regular internal structure. (Metallic glasses, which can be extremely hard, are sometimes used for their high wear resistance and unique optical properties in watch cases – recently Audemars Piguet released a version of its 16202 Jumbo with a metallic glass bezel).
The other side of the coin is that the longer an alloy takes to cool, the bigger the crystals have a chance to grow. Iron-nickel meteorites began forming at about the same time as the Earth and other solid rocky planets in the Solar System, which is a very long time ago – over four billion years. The planetoids that would eventually become meteorites consisted of layers of minerals, with the heavier stuff – including iron and nickel – sinking towards their cores, and taking millions of years to cool. The multi-million year cooling time allowed for the formation of enormous iron nickel crystals, and when you cut an iron-nickel meteorite in cross section and etch it with acids, you can see the crystals, forming a pattern called a Widmanstätten pattern, after the German count and scientist who observed them in 1808.
The source of the meteorite for the DB25 Starry Varius Aérolite Tourbillon is the cosmic visitor known as the Muonalista meteorite, which was formed when the planetoid from which it came, was shattered in some unknown violent cosmic collision hundreds of millions of years ago (the event is recorded in the shock patterns in the crystal structure of the meteorite) Over the slow course of the eons, a fragment of the planetoid’s core fell to Earth, impacting about a million years ago. Since then, the meteorite has gone through four Ice Ages and when it originally landed, modern humans had not yet evolved, so it represents – like the star field on the dial of the watch – an almost incomprehensibly deep gulf of time.
The story is of course even older than that. Iron, like the other heavy elements, is only formed in the cores of massive stars that end their lives as supernovas. Even before the formation of the solar system, the iron atoms in the meteorite dial were forged under forces of unimaginable intensity, in one of the most violent events in the known universe.
The DB25 Starry Varius Aérolite Tourbillon, is, in a way, a visual representation of time across scales immediately perceptible to the human senses, all the way to cosmic scales which defy the human imagination. As a mechanical and physical summary of the nature of time itself, and the human relationship to time, it has few rivals – one of the best examples in watchmaking of Denis Flageolet’s observation that watches are not just timekeepers, but objects of cultural and artistic expression as well.
The De Bethune DB25 Starry Varius Aérolite Tourbillon: case, 42mm x 10.3mm Grade 5 titanium, with openworked lugs; sapphire crystals front and back; 30 meters water resistance. Dial, meteorite, etched, heat-blued and polished, with white gold pins depicting star positions. Movement, De Bethune caliber DB2109V4, 30 second tourbillon, running at 36,000 vph/5Hz in 43 jewels with twin mainspring barrels, deadbeat/jumping seconds complication.