One of the key components of any good tool watch is luminescent hands and markers. A watch doesn’t do much good when you’re deep underwater, stuck in the woods at night, or really anywhere up shit creek if you’re unable to read it. Lume was a logical yet major achievement for tool watches that’s now been around for a little over a century.
Currently, most watch manufacturers use strontium-based Super-LumiNova, while some still use tritium. LumiNova is great because it’s non-toxic, doesn’t degrade if kept from moisture, and glows brightly after light exposure. Purists like to opt for tritium since it requires no help from light, and replacing its luminescence many years down the road is often a nice yellow aging. Tritium is radioactive, mind you, so please don’t lick your dial.
Neither LumiNova nor tritium was the pioneer of luminescent materials, however, that title goes to radium. Discovered in 1898 by Marie Curie, radium is known for being highly radioactive and unstable. The benefit of its instability is it can be used in combination with a material like zinc sulfide to glow. The drawback of its highly radioactive nature is the adverse reaction in humans. Curie would later die of leukemia, and it wouldn’t be a stretch to speculate the cause being radium exposure.
Unfortunately for many folks, radium’s dangerous properties were not discovered for many years – paving the way for radium’s use for a good period of time. Instruments like watches were the perfect application for radium, and several companies popped up specializing in such use: United States Radium Corporation, Radium Dial Company, and Cold Light Manufacturing Company.
Blancpain Fifty Fathoms with radium dial — Courtesy of TimeZone
Women were often hired to paint the dials, and were very directly exposed to the radium. The chemists extracting the radium and getting it into a useful state knew of at least some of the dangers of radium, and protected themselves accordingly (with lead screens, no less – how ironic). The women, completely unaware, were actually encouraged to touch the paintbrushes to their tongues to keep the points sharp. Obviously, this is a pretty efficient way to over-expose one’s self to radium. It’s quite likely all women working with radium in this manner were stricken with some sort of illness, be it anemia, tumors, or degeneration of the jaw. The scandal actually led to several women suing the United States Radium Corporation, which ultimately set precedent for individuals suing a company for on-the-job sickness.
Radium was a damn good luminescent material, and at the time, it couldn’t be immediately replaced. It was used all the way through the 1950s and into the 1960s, with more care taken to those dealing with painting and production. Studies on radium workers showed a major drop in related illnesses, nearly making the dangers non-existent. Nonetheless, as the 1960s rolled on, radium use was finally discontinued in favor of other materials, one of them being tritium. Although tritium is radioactive itself, it emits beta radiation, which doesn’t pass through the skin, making it much safer than the gamma radiation of radium. From there, radium has been all but dead to the watchmaking world.
Rolex Submariner ref A/6538 — Photo courtesy of Stefano Mazzariol
An early example of tritium replacing radium is on the original MilSub, the Rolex Submariner reference A/6538. In 1960, The Ministry of Defense sent every issued example they could to their in-house watchmakers for a tritium re-lume. A/6538s that had been re-lumed sport a circled “T” on the dial, signifying tritium. The lume jobs typically weren’t perfect, and it’s one of the only times a re-lumed vintage Rolex will maintain its value.
Watchmaking has often gone step for step with modern technology, and the addition of luminescent materials is a fine example. It’s a shame that in the case of radium, the progress came with a sad mark of occupational hazard. Radium’s excellent glow may have been too good to be true, but it pushed innovators to find a worthy, but safe, replacement. For that, we can thank radium, and enjoy our aged tritium Rolex and Omega dials, and brightly glowing Doxas and Luminoxes.
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