How Tritium Lights Up Watch Dials

A question about my Rolex which is a 1959 GMT Master.

I just had the watch completely overhauled which included grinding out scratches from the case and oyster bracelet. The watchmaker did a wonderful job with it. It looks absolutely new.

The dial has been refinished so I did not hesitate to have it done again. If it were original then I would have had to have thought twice about it. Rolex, as you probably know, has their “Dial Exchange” program but then you don’t have the original dial.

My question is, with the new tritium (which is white), is there some “breaking in” period for the luminescence? The dial just doesn’t glow for very long (1 hour maximum) but I should tell you I have only had the watch back for 2 days. I recall, in the past that it glowed all through the night and was bright at 4 or 5 a.m. I noticed with my new Minerva, which is the only new watch I have bought in many years that it did not glow well at all when I first got the watch. Several months later, it wasn’t bright in the early morning but it was bright enough to be clearly legible. Is this what I can expect from the new tritium or does it vary from refinishing center to center?

Thanks in advance for any insight into my question.


David A.B. Smith

Posted by Justin Time on December 12, 1997 at 6:43:40:

In Reply to: Tritium question on dial refinish… posted by David Smith on December 12, 1997 at 5:15:13:


First let us dispel a few myth-conceptions about how tritium works. Please do not be offended, but the tritium myths are quite entrenched in many watchlovers’ mind.

Tritium paint on watches is a mixture of tritium and phospor. Tritium is naturally radio-active and needs no external source of light or charge to work. Tritium does not glow. As it decays, tritium emits beta radiation, which is a bunch of excited electrons that in turns excite the electron in the phosphor atoms making them emit photons, or light, as they return to their ground (non-excited) state: the phosphor GLOWS. Phosphor can also be excited by UV light from the sun or other light sources. Thus, the tritium paint relies on tritium radioactivity to make the phosphor glow in the dark, not any charge from external light source.

Tritium, has a half life of 12.3 years, a half-life is simply the time it takes HALF of the tritium to decay. So, as long as you have enough tritium in your paint, the watch will glow in the dark for years, not hours or days, without any need of charging. If your watch stops glowing after an hour in the dark, it means that the glow came from the light exciting the phospor atoms, not from the tritium. In other word, most of the tritium in your watch is GONE! This is quite possible even with a fresh coat of tritium paint if that paint has been sitting around in the watchmaker’s shop or supplier’s shelf for years. The 12.3 years of half-life starts from the second the tritium is born (i.e. freshly produced), not from the time the paint is applied to your watch.

Get another coat of fresh tritium paint, and your watch should glow in the dark for years.

Justin Time