Different Properties, Different Advantages - (more)
by Ned
The mildly radioactive beta particles emitted by tritium constantly excite the phosphor coating the glass vials (if it is Tritium gas vials that are used), or excite the phosphors in the paint used. For about a dozen years whatever has this luminous treatment applied to it will glow. The major advantage of tritium systems is that they produce light independent of their exposure to ambient light. They are also generally brighter than photo-phosphorescent systems after both have been in the dark for a couple of hours, and tritium system's light output stays more or less constant through out the night. Their disadvantages are the fact that they will produce light for a limited number of years. They are roughly half as bright after about 10 years, and they continue to decline in brightness until they are not bright enough to have useful luminous properties (about 15 years or so after application). Another disadvantage is that they can not be used in environments where radiation detectors are in use, as they can trigger alarms and cause other associated nuisances.
Maraglo is a specially treated and specially applied version of Luminova - a specially formulated photphosphor (light excites its molecules to emit photons, ie. light, instead of radioactive particles). It is generally regarded as the best of the non-tritium materials in terms of its combined brightness and the persistence of its luminosity after light exposure. Most people cite the figure "10 times as bright" when comparing Luminova to conventional phosphors. In fact when you consider brightness after several hours it is even better than that, and Maraglo is superior to regular Luminova. It's advantages compared with tritium are:
it should (if protected from, excessive heat, UV light and water) have a longer useful life than tritium systems;
it is non-radioactive, and, therefore can be used in more environments, and without any fear of radiation exposure (although tritium is also generally regarded as safe if kept in the watch),and,
for a time just after it is recharged by exposure to light, it is brighter than even tritium gas vials (this superior brightness, however, is lost after something like an hour or two (depending on a lot of factors).
Hopefully, others will have more information and other opinions to add to this summary. Bottom line for me is that tritium glass vials are the best. Tritum paint next, and Maraglo third. Although I hasten to add that this whole question would be secondary for me, and well behind many other factors, like what movement, dial legibility, cost, and so on.
Posted on Jan 1, 2002, 8:56 PM from IP address 24.128.186.19