The Best and the Brightest

by Craig Hester

There is no shortage of superlatives when it comes to the marketing of luminosity in watches. Brightest, longest, first, most, and best are just a few of the words watch companies proclaim, especially those that tie the visibility of their watches to the core of their brands. In this second of a two-part series on luminosity in timekeeping, International Watch examines watch companies whose brands are intrinsically tied to how well their dials can be read in the dark. Names like Luminox, Traser, Ball, and Reactor, among others, are market leaders in this category and were indeed the first or most active in many areas of illuminating watches. Without question, they have played a key role in the advancement of both the technology and popularity of night visibility in timekeeping. And, not surprisingly, they are fierce competitors.

As in the first installment, this segment focuses on the two major types of illuminating materials on the market, or combinations thereof, with an emphasis on the brands that use them extensively.
The two most common methods of making watches visible in the dark are painted, or stylus-applied, luminous crystal materials and tritium-filled gas tubes.
The more prevalent of the two is a chemically initiated polymer typically coated with zinc sulfide, collectively and more commonly referred to as “lume.” This consists of ceramic crystals and utilizes harmless, non-radioactive aluminates to produce its glow. The phosphorescent crystals collect and store ultraviolet or artificial light and then release it in the dark like a light battery. The advantage of lume is that it can glow quite brightly immediately after a charge and it adds only pennies to the final cost of a watch.
The other material overcomes the major disadvantage of painted lume, which is that it fades between charges. In contrast, tiny glass vials filled with the low-energy, beta-emitting gas tritium have a half-life of 12.5 years. They cannot glow as bright as lume when first activated, but they maintain a consistent light level all the time. However, they do add more to the final per-unit retail price, roughly $7 to $10 for each tube.
Like its deadly predecessor, radium—not used since 1968 due to its harmful nature—the tritium doesn’t actually create the visible glow within the watch dial. Instead, it acts as an activator for the luminous materials with which it is coupled. While tritium has a vastly shorter half-life than radium, it actually keeps the materials glowing significantly longer—and without the deleterious effects.
The radioactivity of the radium also burned out the luminous material relatively quickly, so that centuries before the radium would decay, the lume disappeared. The considerably milder tritium alleviates this problem, as it doesn’t destroy the material it is intended to illuminate.
The decay rate of tritium is so mild it cannot even penetrate human skin and the capillary glass tubes that encapsulate the gas are small enough to adhere to the indicators and dials of watches.
Nearly every watch on the market with luminous material on the dial, hands, or bezel uses either one or the other of these materials, with a few notable exceptions where they are combined. The companies that have built their brands around how well you can see them in the dark took these base materials and improved or expanded them in significant ways.

MB-Microtec
When it comes to tritium tubes, all of the featured brands rely on one source—MB-Microtec of Switzerland. MBM is the market leader in GTLS (Gaseous Tritium Light Source) technology for watches and makes the smallest tubes on the market under the trade name Trigalight.
“We started manufacturing the tubes in 1969 when laser technology became commercially available and have been perfecting the process ever since,” says Sandro Schneider, CEO of MBM. Lasers are used to seal the gas tubes. “We haven’t nearly reached the bottom of all tritium tube technology has to offer, but our process to date results in the smallest and most accurate tubes available,” Sandro says. “They are even small and light enough to affix to a second hand.”Despite the relatively low emissions of tritium, its importation is controlled by the US Nuclear Regulatory Commission and requires a special license and strict procedures.
“The NRC has approved our tubes to be safe,” Schneider says, “And not once in the more than forty years of importation has there ever been any reported harm to the public or a single person.” MBM guarantees their tubes to glow for ten years, and they will have a visible glow for up to twenty-five. Once they fade, the tubes can be replaced by MBM. Schneider couldn’t provide a specific cost as each situation is different, especially if the watch itself needs other repair. But something in the range of $10 a tube, possibly more, is a reasonable expectation. Schneider recommends getting a quote from MBM.
MBM’s history goes back to 1918, so it has been a witness to all the major innovations in watch illumination over the past century. The company even purchased radium directly from Marie Curie herself in the late 1920s when the element she discovered was used in many illuminating applications. In 1950, MBM switched to other materials before radium was banned two decades later.