By Trevor Rowell

Tritium paint has been used on the hands and numerals of watches since the 1930's. At first this technology was Top Secret and restricted to use on military watches.

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 are a group of excited electrons that in turn 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 there is enough tritium in the paint, the watch will glow for years.

Due to the toxicity of tritium based paint, a new technology was developed by mb-microtec in Switzerland. This uses tritium gas sealed in vials. The principle is the same but the tritium gas causes the coating on the vial to glow. The levels of radiation are so small that they pose no risk to the wearer. This technology has been used in the Traser H3, Luminox and Marathon military watches. In recent years SRB of Canada have developed a similar system, this is used by manufacturers such as Smith and Wesson, Rescuer and NITE. SRB tritium is not as yet as well developed as the mb-microtec technology, only offering around 80 - 90% of the luminescence.

The main advantage of tritium in military watches is that there is no additional drain on the watch battery to power the night light source, however these watches do have a drawback in that they can be picked up at great distance by night vision equipment. It is therefore important that these watches are covered during military operations at night.

As the technology has become cheaper it is finding its way into the civillian market. Many sportsmen such as anglers and shooters wear tritium based watches with Luminox and Traser being the most popular.

Each year more and more manufacturers are bringing new tritium watches onto the market. As the tritium light sources from SRB become more popular and combined with cheaper production in China, it won't be long before we see tritium used in purely civillian watches.

Copyright 2006 Trevor Rowell

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