Radioactive Watch Has Us All Aglow

Photo: Courtesy Luminox

Lots of watches glow in the dark, but not for long.

The most common technique is to use phosphorescent paint — it’s activated when exposed to light, though the glow begins to fade moments after the coated elements are removed from the light source. There’s also Indiglo, Timex’s patented, push-to-light system which requires you to push a button to activate a battery-powered light source. Both work alright, but neither are ideal.

I’ve found a promising alternative in an illumination technology from Swiss manufacturer Luminox, which claims to make the markings on its watches always visible, 24/7, with no activating light or battery needed. This is cool, a watch that glows all the time.

The watch I tested, the Valjoux Field Chronograph, lights up using micro gas lights — borosilicate glass capsules, chosen for their resistance to breakage, are filled with radioactive tritium gas. As the tritium decays, it releases electrons, lighting up the hands and hour markers (all without harming the human wearing it). Even the bezel becomes visible in darkness.

Watches using this tritium illumination technology are very popular with military and law enforcement — people who need to be able to read their watches in all conditions, from under water to pitch-black darkness. Luminox is a trusted supplier in these circles, and the military influence is immediately obvious in the Valjoux Field Chronograph’s butch design. With its buckram-like thick buffalo leather wristband and its 48 mm, black steel case that weighs over a quarter of a pound, this handsome watch exudes a sense of adventure-seeking masculinity. While I’m sure the name “Valjoux” warms the hearts of those in the Luminox marketing department, a more descriptive name might simply be “Balls.”

The Valjoux Field Chrono has a screw-in crown and is water-resistant to 100 meters. The textured, white-on-black dial centers make the hour and minute hands, as well as the pair of stop-watch chronograph insets, sharp and very readable. The three-hand chronograph is activated with a firm press of two buttons that sandwich the main crown.

While Luminox’s battery-operated quartz watches are well-known, the Valjoux Field Chronograph is an example of the company’s recent expansion into automatic mechanical movements. Every swing of your arm energizes the Swiss-made Valjoux 7750 movement by spinning its engine-turned rotor. There’s never a need for a battery. Of course, this means that when the watch its off your wrist, and after its 36-hour reserve power has expired, you’ll need to reset the time. As with all automatic watches, you also need to kick-start the movement with 10 to 20 clockwise twists. It’s a minor inconvenience, and one you’ll never encounter if you wear it every day (or close to every day). The back of the watch is dominated by a sapphire crystal, which provides a see-through exhibition case so you can study the automatic mechanism.

The manual that comes with the watch advises: “A mechanical watch is somewhat less accurate than a quartz watch.” As far as I can tell, this is just for liability reasons. I encountered no perceptible loss or gain in a week-long test of the Valjoux Field Chronograph. In fact, my only pet peeve has nothing to do with time-keeping — it was the less-than-comfortable fit of the bulky wristband. But I balanced that with the thrill of taking people into an unlit closet to see their “Oh wow” reactions by the light of the brightly glowing dials.

WIRED Tritium illumination keeps the hands and hour markers visible even in total darkness. The chronograph watch design is handsome. Mechanical auto-winding movement is accurate and has a 36-hour reserve. No batteries required, ever.

TIRED Tritium has a half-life of 12.5 years, so the watch will lose half its brightness by the end of 2024. Second hand doesn’t light up, so chrono is tough to see in the dark. Ultra-thick buffalo leather strap and steel buckle are too bulky for most wrists. Though watch nerds may find $2,300 a fair price, that’s as high as the Swiss Alps for everyone else.

The automatic movement's workings are on display. Photo: Courtesy Luminox