Copyright 2006 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.
About the author:
Trevor Rowell served for 16 years in the British Army and is
currently involved in the development of new technology for
military and police applications. The military watches mentioned
in this article are available from
http://www.telford-services.com
