These days watches that glow in the dark are nothing unusual. The dial and hands are charged by the power of the sun or artificial light, ensuring they can be seen in the dark. Unfortunately this effect is not long-lasting: The luminescence of most luminous materials fades noticeably after about 30 minutes. For everyday use and the average watch wearer this tends to suffice.
The case is very different however for watches those are used for military purposes, in extreme conditions or in poor visibility underwater. In such conditions any reduction in luminescence can prove disastrous, so luminous materials are used that keep the dial constantly bright and do not require an outside light source. A successful solution is to use luminous gas light sources: millimetre-thin glass tubes that are filled with tritium and can be applied to the hands and dial.
Swiss watchmaker DAVOSA uses these gas tubes to equip its popular Argonautic model series. This resilient divers’ watch with its helium valve and ceramic bezel is now available as an Argonautic Lumis Automatic and Chronograph, retailing at 698 and from 1,598 euros respectively.
Tritium is a colourless gas otherwise known as extra-heavy hydrogen. The name originates from the Greek word ‘tritos’ meaning third, and refers to the three components of the atom (3H). Tritium has been used for decades in all sorts of applications where constant, independent and long-lasting light sources are essential. On the dials of military watches you will often find a red, circular symbol with the notation ‘3H’ that refers to the use of tritium. In ‘civil’ watches, the abbreviation ‘T25’ denotes the same thing. In the past, luminous tritium was applied directly to the dial.
Today’s watchmakers are more careful and fill the gas into fine tubes made from borosilicate glass, a highly resilient and ISO-certified glass used in chemical engineering. These Gaseous Tritium Light Sources (or GTLS) are not only exceptionally safe; they also guarantee the watch wearer at least ten years’ constant luminance – without any external energy source.
For a divers’ watch like the Argonautic, a dial that is illuminated by means of gas tubes brings additional reliability and independence. Neither a depleting power source nor a lack of light can impair the function and readability of these watches. Thanks to their mechanical, selfwinding mechanism and their self-illuminating tritium tubes, they make the wearer completely self-sufficient.
Like all the other models in the series, the Argonautic Lumis is water resistant to 300 metres, possesses a robust ceramic bezel as well as a helium valve that is suitable for professional diving purposes.
Automatic: 161.509.20 black/white, 161.509.60 black/orange
Chronograph: 161.508.20: black/white, 161.508.60 black/orange, 161.508.80 PVD gun-plated
– GTLS (Gaseous Tritium Light Sources) – tritium gas tubes with 10 years’ guaranteed luminescence
– Resilient ceramic bezel
– Water resistance to 300 metres (30 bar/1000ft)
– Manual helium valve
– Sapphire crystal
– Stainless steel case (316L)
– Solid metal strap with diving extension and rubber strap with safety buckle, NATO strap (orange/grey/black)
– Mechanical automatic movement
– Calibre: ETA Valjoux 7750 (Chronograph), ETA 2824-2 (Automatic)
– Screwed crown, helium valve, Chronograph pushers
– Screw-down steel back
698 Euros (Automatic), 1,598 Euros (Chronograph), 1,698 Euros (Chronograph with PVD coating)