Marcus Hanke
[PuristSPro Moderator]
11296
Some thoughts about the tritium issue ...
First of all, we should get rid of a slight confusion in terms: It is not the tritium that is shining at night. If it were, you really had reason to be worried, since radioactivity strong enough to be luminous is certainly not harmless. What is causing the luminence is phosphorous. This material can 'store' , or better: transform energy and emit it in shape of light. However, it needs an energy source for that. 'Charging' it with strong light is a possible means, but phosphorous cannot store this energy for long, so the luminence will fade very quickly.
Therefore, the phosphorous particles are 'backpacking' their own energy source, by being combined with tritium, a material of decent radioactivity. It emits enough energy to constantly stimulate the phosphorous. However, the big problem of tritium is its short half-time of 12.3 years. That means that within 12.3 years, the tritium loses 50% of its energy level. This reduction can be seen on watch dials, when already after six or seven years, the nighttime luminscence is visibly reduced.
Regarding the yellowing: Neither tritium nor the phosphorous is subject to colour changes over the time, but the binding agent is. This is the 'glue' holding together the particles. There are different materials used, so there are watches that do not show significant colour chances on the luminous markers, some do so more. I have seen markers becoming grey (Fortis), others becoming yellow (IWC, Eberhard). Until now, my only Union with luminous hands (white colour) does not show any colour change, nor do the greenish 'tritium' markers of my old Glycine. However, other factors, like UV-radiation from exposure to bright sunlight, might influence the colour change as well.
As long as a specific watch model is produced with SuperLuminova dials, a tritium dial will probably be replaced during a complete service of the watch, if the tritium has become too weak already. If it is an older watch, it is possible that the olde luminous mass is removed, and a new substance is applied, but without tritium. Sometimes the luminous capacitiy is thereby improved, sometimes not really.
'With best regvards,
Marcus
Senator navigator and Tritium