How do luminous hands work

Two of the best known users of tritium gas tubes for watch dials are Ball and Luminox. Tritium paint for watch dials and hands will lose its ability to photoluminesce over time, although as with promethium, degradation of the phosphor will take place more slowly, as tritium is a much weaker radiation source. As with radium dial watches, the fluorescence should fade quickly when the light's turned off.

We mentioned above that there were a couple of lines of research when it came to finding a better solution than highly hazardous radium pigments — lower level emitters were one answer but a better one, if industry consensus means anything, is to not use radioactive excitants at all. To get away with this, you need a phosphor that will glow enthusiastically for hours after exposure to light — something that will act as a sort of "light bank," emitting stored energy in a measured fashion.

Enter Luminova. Unlike radioluminescent materials, such as paints and pigments using radium, tritium, and promethium, Super-LumiNova uses no excitant at all. Instead, it incorporates a material known as strontium aluminate, which is an extremely efficient phosphor that once charged, will glow very brightly initially, and with diminishing intensity for several hours thereafter.

For strontium aluminate to be an effective phosphor, it must be combined with europium, a non-toxic, non-radioactive chemical element. Strontium aluminate is a much more efficient phosphor than zinc sulfide — it's about ten times as bright and glows about ten times longer and the color can vary between various shades of green and blue, with blue supposedly producing the longest glow time, and green offering better brightness.

The disadvantage of Super-LumiNova in comparison to radioluminescent material is of course that its brightness fades until it's recharged by another exposure to light. Personally I've found that with most of the sports watches I've owned over the years, if my eye's dark-adapted the watch remains legible, with some difficulty, through most of the night. Still, it is a disadvantage of the material relative to the always-on glow of radioluminescent solutions which is part of the appeal of Luminox and Ball.

Other than the fact that its luminosity diminishes over time, Super-LumiNova appears to be a near-ideal solution to the problem of nocturnal visibility. Strontium aluminate seems to be a highly stable phosphor, and Super-LumiNova dials, at least thus far, appear to not suffer from the gradual phosphor degradation characteristic of radioluminescent materials.

It is adversely affected by moisture, so a high humidity climate might cause issues, but in general, Super-LumiNova and other strontium aluminate-based pigments seem likely to be with us for a long time.

Exactly how long Super-LumiNova will retain its ability to glow is unclear — it seems safe to assume that sunlight can cause the material to break down eventually and if the vintage watch craze has taught us anything, it's that nothing lasts forever; but it seems, in general, a very durable material.

I'm old enough to remember seeing radium dial watches in actual use barely; I was very young, but anything that glows in the dark makes a great impression when you're four and while I miss the brilliant radiance of radium dials and hands, it's probably just as well for all concerned that the industry got out of the business when it did. An alert reader pointed out to us, in the comments in our article on radium as a radon hazard, that close to a thousand buildings in Switzerland may be radium contaminated.

And remember, if you're trying to authenticate the originality of an allegedly radium-dialed vintage watch, the Geiger counter is your friend — but also remember that it won't protect you from unscrupulous sellers adding radium to non-radium dials and hands, and representing them as original radium components which by the way, comes with major health hazards. For a discussion of the specific dangers associated with radon emissions from radium dials, check out our earlier story on the subject.

Ask them. Skip to Main Content [enter]. Jack Forster July 05, What Makes Dials Glow. Radium Paint. Emitting only beta particles at lower energy than radium, promethium is generally regarded as an option with a much lower risk of dangerous side effects. In other words, a watch featuring promethium on its dial is only likely to glow very weakly, for a few years.

Even still, Seiko used promethium as an excitant for a brief period of time. Another radioactive lume still found today involves the use of tritium gas. Encapsulated in a tube of glass coated with a phosphor layer, the phosphor glows as the tritium undergoes beta decay. Because of the glass tubing, tritium gas is a very low-risk radioactive material. When compared to Super-Luminova, tritium offers the benefit of a constant glow regardless of the ambient light — perfect for applications where you need a watch with dependable, fade-free luminosity.

Several manufacturers — such as Ball, Luminox, and Marathon — use tritium gas today. Here are two of our picks for the best tritium watches:. Built to be life-proof, this watch features a reinforced polycarbonate case, a Swiss-made Ronda quartz movement, and a sapphire crystal. With aggressive styling and a durable construction, the Hawk tritium watch is an adventure-ready accessory providing constant, bright illumination. From the Ohio-based Ball comes the Engineer Hydrocarbon Original, a handsome, hard-wearing watch designed to stand up to the daily rigors faced by the most demanding of technical pros.

But the most striking quality of the Engineer Hydrocarbon Original would undoubtedly be its use of 30 tritium gas tubes to illuminate the dial. Electroluminescence EL describes the process of charging a phosphor with an electric current in order to produce light. It relies on the use of powders and thin films as semiconductors, with the addition of active materials such as copper to give the EL panel its color. First adopted for commercial use during the s, thin-film phosphor electroluminescence offers even illumination with little battery drain.

Although Timex is one of the most steadfast supporters of EL lume, others such as Casio have also taken to the technology over time. Compared to Super-Luminova and tritium gas, EL has the benefit of being battery powered. Offering an even glow across the whole watch face, Indiglo can be used on the entire dial or in the digits only as per negative LCDs.

Much like an electroluminescent dial, LED backlights require an electrical current for illumination. They require even less energy than EL, are more efficient for solar charging applications, and are extremely cheap to produce.

Sporting a Red Wing Shoe leather strap and a solid steel construction, this classy piece punches well above its weight class when it comes to style and quality. And with Indiglo Night-Light and 50m water-resistance, this watch is as functional as it is good looking. For instance, its solar battery allows for convenient self-charging and its Atomic Timekeeping technology provides unrivaled accuracy no matter where you are. HiConsumption is reader-supported. They will continuously glow if there is a light source, but the emission of particles occurs on mere nanoseconds.

Hence, most of these materials will go dark right away once the light source becomes unavailable. For watch dials, using fluorescent materials is not always viable. Phosphorescence — Phosphorescent materials also absorb photons from a light source.

The only difference is that they emit those photons as light very slowly, which is why phosphorescent paints are usually used for watch dials. This material is self-luminous, only when freshly applied. There is no need for an external energy source because there is already light emitted from the radium particles' radiation in the paint. Back in the old days, some watches had numbers and indexes with radium paint.

However, given its dangerous effects in health, it is not almost used today in the modern watchmaking industry. Due to the harmful effects of radium paint, promethium and tritium were later discovered as substitutes. Technically, these two substances are considered less radioactive than radium. On the other hand, tritium is also a low energy beta emitter with a longer half-life than promethium. Tritium is estimated to have a half-life of As the search to find another substitute material not radioactive at all continues, and this is where the two super players in the modern watchmaking industry come in; the Luminova and Super-Luminova.

Instead, it uses a material known as strontium aluminate — an extremely efficient phosphor that will glow once charged. It shines brightly initially, then slowly diminishes for several hours. The strontium aluminate needs to be mixed with europium — a non-toxic and non-radioactive chemical element to achieve its perfect glowing characteristic.