Rolex Watch Lume Overview (Radium/Tritium/Luminova)

[Tools]

The modern Rolex watch has a luminous dial and works like this:



Energy, of course, follows a basic principle... It cannot be destroyed, and can only be transformed, so this leads us to the idea behind the luminescent watch dial; converting known energy into a bit of light.

Luminescent material by itself does not glow, it needs an energy source. That energy can either be radioactivity for our Tritium excited, or radioluminescent watch dials, or a light source for our photoluminescent dials.

Now that we have decided on these two different types of energy sources, we need some luminous materials.. Either flourescent material or phosphorescent material, with the former being short term and the latter being more suitable for a longer term; the logical choice is phosphorescent material. This phosphorescent material is mixed into a paint matrix and is ready for our purpose, applying to the watch dial and hands.

Our energy source excites the electrons within the paint matrix, the excited electrons generate heat, but also generate photons given off as visible light.

When the phosphorescent paint matrix includes Tritium, it is always excited and therefore always gives off visible light until the radioactive life of the tritium source is depleted, therefore, radioluminescent material is "always on".

Our non-radioactive dials use an invention, Luminova or Super Luminova, that is excitable by light itself, the electrons are excited, and the result is once again visible light. The downside of a light excited paint matrix is that once the light is removed, the residual excitement of the phosphorescence gradually lessens and returns to a non-excited state, requiring constant re-charging.



Here is a brief overview of the various Luminous Materials.

Radium:

Up until about 1960, Rolex used the radio-active material Radium to coat hands and indices of their dials. The Radium markers were extremely efficient where bright luminosity is concerned, but also much more radio-active than the successor, Tritium.
Workers at the Rolex manufactory and other watch and clock shops, applied the Radium by hand; or rather by using a fine painting brush. To apply the Radium exactly to the places where it was supposed to be, workers would tend to lick the tip of the painting brush to get a sharper point, thus being better able to apply more accurately the Radium. This habit of licking the painting brush resulted in numerous cases of workers getting cancer, especially mouth cancer. But as stated, Radium was used up until 1960, where popular use finally ceased due to serious health risks.

The dials having Radium as luminous markers would read "SWISS" at six o' clock.

Tritium:

Tritium was used from 1960 to 1998. Also being radio-active, but more mildly so (beta waves). The half-life is approx. 12.3 years. After that, Tritium (in most cases) will not glow anymore.
There were two degrees of Tritium dials:

a) the dials emitting radio-activity of less than 25 mC. Dials are marked "SWISS T < 25"

b) the dial emitting radio-activity of less than 7,5 mC. Dials are marked "T SWISS T".

To describe the intensity of the radio-activity of the Tritium markers, a thin sheet of Aluminium is able to block Tritium beta waves. Thus, the Oyster case and crystal were said to be sufficient guard to prevent any harmful radiation to the wearer of the watch. The radiation a person gets from the normal background radiation found in nature exceeds the radiation emitted from a "T < 25" dial.

As a side note: Besides the "half-life degression" of the Tritium, hands and indices applied with Tritium have often been known to discolour to a more brownish tone by age. Some say that factors like UV rays and humidity play a role. Therefore, not ALL Tritium dials discolour. It depends on what environment the dial / watch was kept in.

(Super)Luminova:

A Japanese invention from the company Nemoto, the non radio-active substance, Luminova, was introduced in 1998 when Tritium was (at least widely) banned. Time spans for the use of Luminoa is:

a) 1998 - 2000: Dials (again) marked "SWISS" at 6 o' clock

b) 2000 - : Dials marked "SWISS MADE" at 6 o' clock.

The terms "SuperLuminova" and "Luminova" describe the same paint compound. Technically, there is no difference between the two, but "SuperLuminova" is a term reserved by Nemoto's European partner, Tritec.

SuperLuminova is not (yet!) known to discolour by age. But SuperLuminova is quite fragile and does not like humidity which can make it crumble. Some companies solve this issue by applying a thin coat of clear lacquer to the markers of the dial.

Luminova and SuperLuminova are the same patent and come in a number of different colors.

Here is a chart with relative brightness. New Chromalight is light blue.
Note it is ISO standardized with a ~30 second excitation time.


(sources: Luminous markers and this article.)


__________________

[Scarface]

Awesome info

[GMTJOHNNY]

Being a chemist, I love the chemistry.
Great explanation!
Long live Tritium!

[Mr. Clean]

Thanks, very informative!

[mgpdragon64]

Wow! very informative! Thats why a Rolex is still the best watch! thanks

[topcat30093]

Thanks Larry
For this very useful information.

[marke]

as long as nine glows in the dark, my watch i mean i can still be a rolex jedi warrior.....

" the rolex is with me"

mark

[marke]

or " may your rolex be with you"

hahahah for rolex jedi masters....

[Watchonisto]

Good to know

[sheldonsmith]

Here is an example pict that has been floating around the watch boards these last few years. Author unknown...

-Sheldon

[DSJ]

Wouldn't the Tritium material still be half as bright after 12.3 years? My 1993 and 1997 Tritium sights on my old police guns are still quite good.

[entropydave]

Originally Posted by DSJ

Wouldn't the Tritium material still be half as bright after 12.3 years? My 1993 and 1997 Tritium sights on my old police guns are still quite good.

Yep - it's down to the half life... bring back radium salts I say and have them bright for thousands of years!!

[Cujucuyo]

My Omega Speedy has T-Swiss Made-T and you have to be in a VERY, VERY dark place to even see the tiny markers glow. As for Radium, it has a sad story to it:

http://www.runet.edu/~wkovarik/envhist/radium.html

And it involves watches, go figure.

[marke]

Wait until you see the LUME on the new deep sea, I tried it on yesterday and the LUme is stunning/stonking.....

[topcat30093]

Originally Posted by marke

Wait until you see the LUME on the new deep sea, I tried it on yesterday and the LUme is stunning/stonking.....

Heh Marke
You couldn't resist could you

[entropydave]

Originally Posted by Cujucuyo

My Omega Speedy has T-Swiss Made-T and you have to be in a VERY, VERY dark place to even see the tiny markers glow. As for Radium, it has a sad story to it:

http://www.runet.edu/~wkovarik/envhist/radium.html

And it involves watches, go figure.

I can't imagine what it must have been like using Ra as a lume....horrific cancers and so on - plus the fact that if you restore old watches you are exposed to fine dust that you do NOT want to inhale!

[mwillems]

Nothing wrong with Ra is you handle it carefully - the problem is not in the watch users, the problem is in the making. Read up on the "Radium Girls" (Google the term) - that was bad.

But today I think we could do it with little danger to user or maker. Only the political climate is against it.

[videobob]

I've got a "S" model Sub, (1993) SWISS-T<25 and its dark as midnight, no glow at all!!!

[harlansmart]

Wow - so the lume on Rolex dials is a Japanese idea - great info...very informative!

[entropydave]

Well, I had a bad night's sleep last night and I can tell you I was pretty impressed with my lume! It was certainly still easily readable some 5 or 6 hours after being exposed to ordinary domestic lighting (ie no blasting with my UV torch!)
Also I noticed that when I break out the telescope and I am fully dark-adjusted, again, I can read the time easily for as many hours I am out observing.
So, wearas I would much prefer the original Radium lume ((in preference to tritium), this is pretty much good enough. Never really paid attention to the lume until last night!

[Trurolexer]

Very nice review!!!

[Ike]

One thing I find a bit odd is that my dad's DJ that he bought new in the 70's still glows in dark rooms and glows bright for several seconds when charged with a flashlight. It is marked T swiss T.

My DJ that I bought pre-owned is from the late 80's to early 90's from what I can tell. It is also marked T swiss T. It will not glow at all, even when it is left with a light source for several minutes.

[jtvision]

My DJ which was produced in the third quarter of 1985 is no longer glowing.
My new DJ from 2005 is spectacular.

[Nods]

Very informative, I am off to research Radium Girls sounds like a sad and interesting story.

[tomee]

Originally Posted by xjeeunitx

What about the dials that says "T SWISS MADE T"

tritium

[bballchamp]

Thanks for the great info!

[aelvin]

ah... i learned something today!!!

[Alcan]

I think maybe its time to have the Tritum lume on my N serial Sub hands and dial redone.

[pablofields]

Question in light (pardon the pun) of this part of Tool's thread starter:

"(Super)Luminova:

A Japanese invention from the company Nemoto, the non radio-active substance, Luminova, was introduced in 1998 when Tritium was (at least widely) banned. Time spans for the use of Luminoa is:

a) 1998 - 2000: Dials (again) marked "SWISS" at 6 o' clock

b) 2000 - : Dials marked "SWISS MADE" at 6 o' clock."


All of the replacement Lume dials I have seen on 1655 Orange Hands are marked "Swiss" rather than "Swiss Made". Does this mean the 'modern' 1655 replacement dials were all made between 1998-2000? And if so does that suggest Rolex might not continue producing replacements if and when this supply runs out?

[Tools]

During the transition years 1998-2000, Dials were marked "Swiss" until Rolex finally settled on "Swiss Made" for Luminova dials.

Very early Radium dials were also marked "Swiss" until radium was outlawed in ~1960.

Rolex also continued using "Swiss" dials for several years as Service Replacements after 2000..

So, looking at a serial number that should be 1996, but we find it with a "Swiss" dial; would indicate a service replacement and not a "transitional"; likewise, models with "Swiss" dials that have serial numbers later than 2001 would very likely have had a service dial replacement at some point until that stock of dials was depleted..

Service Dials have been seen with some differences from original equipment dials, so I don't think that there is any evidence that a particular dial would stop being produced completely just because the stock of those with "Swiss" on them ran out.... However, at some point they would, indeed, no longer produce a particular replacement dial.