5 Illuminating things about lume

THE FACTS IN CONTEXT

As is often the case with technological advances, need is the mother of invention. Take luminous watch hands and indices, for example. During WWI, officers in the trenches needed a way to tell the time to properly implement their orders. Since attacks often took place in pre-dawn hours, it was important to leave the trenches at the right time, so your command advanced with other units protecting your flanks.

Well, why not simply light a lamp or candle? As dangerous as ranked assaults across no-man's land were in the Great War, showing a light, even in the trenches, invited being killed by enemy snipers. The solution was to use luminous paints on the watch hands and hour indices.

 

FACT #1: LUMINOUS WATCH HANDS SAVED YOU FROM SNIPER FIRE. HOWEVER, IT DIDN'T HELP YOU SURVIVE NO-MAN'S LAND.

Enter radioluminescent paint (say that three times fast) and the second fact in the article, your watch was radioactive! The radioactive material of choice was radium. Sabin Arnold von Sochocky invented the paint in 1908, mixing it with other chemicals to create the first "lume."

 

FACT #2: TO SEE THE WATCH IN THE DARK, YOU HAD TO WEAR A RADIOACTIVE WATCH.

Here's how Wikipedia describes the process by which light is created.

Radioluminescent paint is a self-luminous paint that consists of a small amount of a radioactive isotope (radionuclide) mixed with a radioluminescent phosphor chemical. The radioisotope continually decays, emitting radiation particles which strike molecules of the phosphor, exciting them to emit visible light. The isotopes selected are typically strong emitters of beta radiation, preferred since this radiation will not penetrate an enclosure. Radioluminescent paints will glow without exposure to light until the radioactive isotope has decayed (or the phosphor degrades), which may be many years.

While radium has a half-life of 1,600 years, the phosphor in the paint is consumed in the process of emitting light. This causes the brightness to fade over time and eventually disappear. Many watches from the first half of the last century may no longer glow in the dark anymore. But, put a Geiger counter on them, and their radioactivity will register.

 

"The sharp-eyed reader will notice that the BG W9 lume is highlighted in the chart. That's because we use this lume in our watches for performance and aesthetic reasons. RC TriTech states that all the most prestigious Swiss watchmakers use Super-LumiNova®. LIV Watches is proud to be part of this august group. "

FROM TOXIC TO SAFE

Eventually, the world recognized the dangers of radiation exposure. Indeed, von Sochocky and Marie Curie, the French pioneer in radiation research, both died of radiation poisoning, as did many shoe salesmen. What? Shoe salesmen? Yep, shoe companies provided x-ray machines to aid in "proper fitting." Unfortunately, these were unshielded and were lethal when used for extended periods.

Radioluminescent materials were finally phased out in the early 1960s. Though radioluminescent paint went by the wayside, that did not eliminate the need for being able to read watches and instruments in low light and dark conditions. As an interim step, tritium replaced radium in the 1950s. Though still a radioactive material, it was much less toxic than its predecessor. Tritium is still in use today in watches and other applications because it needs no exposure to light to glow.

 

FACT #3: EVEN KNOWING THE DANGERS OF RADIATION, IT WAS STILL USED ON WATCHES AND INSTRUMENTS INTO THE 1960S!

People get freaked out when the topic of radioactivity enters the conversation, especially when it comes to personal and daily use items. And, for good reason. You'd have to live under a rock, uranium ore excluded, to not be aware of the dangers of radiation exposure.

The Swiss maker of Super-LumiNova® phosphorescent pigments introduced their non-radioactive, high-performance alternative in the early 1990s.

 

GLOW IN ANY COLOR

Unlike Henry Ford, who'd sell you a car in any color you wanted, as long as it was black, Super-LumiNova® pigments can be provided in any color you want using the printing industry's color reference tool, the Pantone Matching System. If you can find it there, you can get a matching lume.

That certainly opens up the style aspect of lume, but some colors are better than others when it comes to the ability of the human eye to see it in the dark. The fourth fact of this article is the human eye sees different colors better, depending upon how long they have been in the dark (not to be confused with being kept in the dark, that's something altogether different:

 

FACT #4: THE HUMAN EYE SEES DIFFERENT COLORS BETTER DEPENDING ON HOW LONG THEY'VE BEEN IN DARKNESS.

Here's what TR TriTech's website says about this tidbit:

The human eye has the highest sensitivity to the green emission, when coming directly from sunlight into the dark (photopic vision). After adaption to darkness, the human eye is changing to scotopic vision with higher sensitivity but no color perception. In such situations, the blue emission is better visible by the human eye.

I suppose scotopic vision is the basis for those blue airport runway lights and emergency phone call stations on campuses. Although, I find that light very unpleasant.

 

While any color can be produced, here are the standard choices:
BL (Blue Line, emission at 485 nm)
GL (Green Line, emission at 515 nm)
VL (Violet Line, emission at 440 nm)
WL (White Line, complete white emission)
YL (Yellow Line, yellow emission)
OL (Orange Line, orange emission)
PL (Pink Line, pink emission)
UL (Ultramarine Line, ultramarine blue emission)

 

FACT #5: NOT ALL LUME IS EQUAL.

The level of brightness produced depends upon the chemistry of the luminous materials used to create each color. Check out the handy chart from RC TriTech. You'll see exactly what I mean.

 

 

WHAT'S NEXT FOR LUME?

The chemists working in this specialized segment are continuing to advance their offerings. Of particular interest to me is the newest offering from TR TriTech, micro-sized cast ceramic indices that contain Super-LumiNova®, LumiCast®.

Let's pause for a minute and let this technology sink in. To help visualize this feat of micro-engineering, look at the indices on your watch. Now, visualize the process by which these markers of the passage of time could be cast. Yes, I am a geek and love the television series "How It's Made." This boggles the mind. Check out the TR TriTech image from their website showing four watch dials with different colors of lume.

While that is cool, the image on the LumiCast® webpage is even more impressive. I grabbed a screenshot, and you can see it below.

 

"LIV hand applies the indices and lume to each of our watches. For our fan-favorite P-51 Pilots (see below), that consists of five layers of Swiss LumiNova on the indexes and three layers on the hands. ​As you might imagine, this takes a steady hand indeed. This amount of lume gives you that super bright luminescence you need for a quick midnight time check. Plus, it makes the dial pop during the day."