Want to clue yourself up on watch lume? Read this article.
For collectors, the quality of watch lume has become almost as important a feature as complications or dial finishing. It’s certainly a notable talking point, especially for tool watches. That’s because glow is important when it comes to professional timepieces. If a tool watch has a weak emitting glow in low-light conditions, it’s not really a tool watch. Collectors can be pretty snobby about luminescent watches. But I actually think the argument for decent glow is a well-justified one.
Luminescence, after all, determines how well a watch performs in the dark. So, if you happen to use your watch more during the day than the night, it’s a pretty important feature. Likewise, whether diving down to ungodly ocean depths, operating an aircraft at night, or exploring a cave, lume will matter to you—a lot.
Today, we’re going to tell you all about lume watches. The science behind watch luminescence is as fascinating as the science behind movements. But watch luminescence is more about chemistry than physics. Moreover, the development of today’s glow technology comes with a storied history!
Table of Contents
What Is Watch Lume?
First things first: What is watch lume? Lume is a material that glows in the dark. Manufacturers use it on hands, hour markers, and other important dial features to guarantee legibility in the dark. Military personnel and anyone who uses a tool watch for work or exploration will appreciate the importance of good lume.
As with all things in life, watch luminosity has varying degrees of quality. While there is no way to directly answer which type is best, we can at least explore the pros and cons of each.
What Is the Best Watch Lume?
Here’s a quick and easy science lesson on the best watch lume. Luminescence is the creation of light from a non-heated source, unlike incandescence, which often uses sources like fire. Today’s most common watch lume is photoluminescence, though tritium and electroluminescent dials are also popular. They all have their strengths and weaknesses. Let’s take a look at them in more detail.
Photoluminescent Paint
Photoluminescent paint absorbs a light source and then uses it to create a glow on watch dials. It’s a non-toxic, non-radioactive solution to other, more dangerous lume technology. Dangerous lumes don’t exist on the new watch market anymore. But knowing about them is relevant to watch collectors even today. This is especially true when you think luminescent material is part of some brand’s history. Take Panerai, for example. The watchmaker became a leader in luminescent material, embarking on a quest for safer, brighter lume. It soon became part of Panerai’s identity.
There are two types of photoluminescence: fluorescence and phosphorescence. The difference between the two is that phosphorescence is long-lived. It continues even after activation, making it perfect for watch dials! Meanwhile, fluorescence is excellent for indoor lighting and neon signs.
Kenzo Nemoto, a Japanese entrepreneur, developed a stable and non-toxic phosphorescent paint using a compound called strontium aluminate in the ‘90s. Swiss brand LumiNova AG brought the base formula into common practice. This Super-LumiNova is still the watchmaking industry’s most common luminescence.
Photoluminescent dials can glow anywhere between half an hour and up to seven hours before needing a recharge. They’re long-lasting and won’t usually discolor or fade the same as tritium gas does. Some brands use proprietary photoluminescent formulas. Rolex’s Chromalight has a signature blue sheen lasting up to eight hours. Seiko’s LumiBrite is a Japanese Super-Luminova.
Radium Dials
Due to the Radium Girls tragedy in the 1920s, watch companies gradually decreased their use of radium dials. Today, we don’t use them at all. So why are we talking about them here?
Even though manufacturers no longer use radium, many vintage watches have potentially hazardous radium dials. Companies began using it during the 1910s before realizing its harmful effects. Those hired to paint dials with this material became fatally ill. Watches stayed in circulation until the 1970s, even though the Radiation Control for Health and Safety Act was passed in 1968.
The universal rule among the vintage watch collecting circle for a long time was that watches containing radioactive materials were perfectly safe. Even if you’re going to play around inside the dial, “just don’t sniff or lick it.” I’m no scientist, but recent studies show that non-ventilated vintage watches can produce radon, which is radioactive. Some devices can measure radiation levels in a watch these days. They have become quite a valuable tool for vintage watch collectors.
Tritium
After radium, tritium arrived. Tritium has almost no radioactivity when under a dial protector, whether mineral or sapphire. Compared to radium’s tan undertones, its glow has a creamy yellow hue. Of course, zero radioactivity is even better than almost zero. And as you now know, photoluminescent glows came out in the ‘90s as an entirely non-toxic option.
Tritium came back into the watch world as a gas, however. These gas tubes provided a dial glow that, in real-time use, wouldn’t fade after a few hours. Still, tritium will lose its long-term glow after 12 and a half years, whereas photoluminescent glow won’t. This makes tritium better in the short term, while photoluminescence is better in the long term.
Ball Watch Company adopts gas tube technology to produce a vast array of different dial colors. Its micro gas tube technology promises a minimum of ten years of glow. The micro gas tubes feature on the baton hands and hour markers of a Ball watch dial. They are lightweight, and Ball seals them with a CO2 laser after coating the insides with phosphor powder and filling them with tritium. What happens after that is a fascinating chemical reaction.
The tritium inside the tubes emits electrons, and the phosphorous coating gives off a cold light. Ball’s micro gas tubes give off a constant, bright, and colorful glow.
Electroluminescence
Electroluminescence glow, or EL, is generated from an electrical current from a conductor behind the dial. At the press of a button, EL glow activates like a flashlight. You’re likely familiar with EL lighting from Casio’s digital watches or Hamilton’s historical catalog. One example that springs to mind is the Timex Indiglo watch. It’s a patented, exceptionally bright electroluminescent glow, though it does use a lot of battery power.
FAQs
Here are the answers to some common questions about watch luminosity.
What Is Lume on a Watch?
Lume is the watch’s dial glow, often painted onto the indices and hands so you can read it in the dark.
How Long Does Watch Lume Last on a Watch?
The lume on a watch varies depending on the material used. Super-LumiNova activates after natural or artificial light exposure but needs constant recharging. On the other hand, tritium has a continual glow but will die out after several years.
Are Luminous Watches Safe To Wear?
Today, luminous material is safe in watches, but it wasn’t always that way. Radium was detrimental to health, and gradually, manufacturers had to phase the material out. By the early 2000s, Super-LumiNova, the Swiss version of LumiNova, had become the new chemical compound to use. Today, it’s the most common material in high-end watches with luminous dials.
Does Watch Lume Fade Over Time?
Phosphorescent material – the most common lume – technically doesn’t fade. However, the paint itself might degrade or come off because of moisture, dust, UV exposure, etc. Even so, it would take several decades. Phosphorescence itself, however, doesn’t “run out” of charge and will always naturally absorb and emit light.
How Long Does Watch Lume Last?
A fully charged phosphorescent dial will need recharging after 30 minutes or several hours, depending on how many layers of paint are on it. Tritium tube watches stay lit as long as they’re in the dark but will fade in the long term.
Can You Change the Lume on a Watch?
Yes, you can mod a watch to change the lume. However, removing parts and safely removing the original paint is a delicate process that inexperienced collectors should leave to professionals.
Conclusion: Lume 101
Photoluminescence is the most common kind of glow on a watch dial. Super-LumiNova is harmless to humans and demonstrates just how far lume technology has come over the years. That said, most criticism of Super-LumiNova comes from its rapid decrease in brightness and sensitivity to moisture.
Meanwhile, electroluminescent lights in digital watches activate with a push of a button. Tritium has a long-lasting in-use duration, making this option effective in tool watches. Furthermore, collectors consider the patina and changing of color in tritium-treated dials a thing of beauty. Choosing which watch lume best suits you depends on what you use your watch for.
Do you prefer the aging charm of a tritium dial, the boldness of Ball Watch Company’s gas tubes, or the huge range of Super-LumiNova colors? Let us know in the comments below!
This is a nice overview of often neglected aspect in the watch reviews. For me that’s an important one, as I often check the time in the dark. And I find it very difficult to find out information on that before buying a watch. (I’ve returned a couple already for that reason)
The picture on the top looks exactly like my Seiko 5, which I use as a sort of benchmark (for lack of other). It might not be the brightest, but it is bright enough and it lasts for most of the night, getting quite faint before down, but still legible. It would be good if it had a different mark on the 12 and 3 o’clock, as it could be surprisingly difficult to tell that in the dark.
It’d be very interesting to see a future post with a comparison of the many watches you have in your collection in terms of brightness and how long they remain legible in the dark.
Also it seems to me the watch manufacturers put the design aspect above the lume every time unless it’s about a field or dive watch.
Thanks for writing on that matter.