Tools
2 February 2008, 08:13 AM
The modern Rolex watch has a luminous dial and works like this:
http://i198.photobucket.com/albums/aa67/LD_album/lume/ExpIILume.jpg
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.
(sources: Luminous markers (http://www.oysterinfo.de/en/detailinfos/leuchtmasse/index.php) and this article.) (http://ulyssenardin.watchprosite.com/show-nblog.post/ti-399346/)
__________________
http://i198.photobucket.com/albums/aa67/LD_album/lume/ExpIILume.jpg
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.
(sources: Luminous markers (http://www.oysterinfo.de/en/detailinfos/leuchtmasse/index.php) and this article.) (http://ulyssenardin.watchprosite.com/show-nblog.post/ti-399346/)
__________________