![]() ![]() Superluminous paints: Luminous paints have come a long way over the last several years.Of course, many customers simply prefer not to have any kind of radioactive tritium product on their wrist, even if it is just a small amount of tritium and even if it has been declared to be safe. Or sometimes, the cost of the tritium dial is partly covered by cutting down on other features (case, crystal, band, etc.), when compared to a non-tritium model in the same price range. The disadvantage is that, due to the relatively high cost of the radioactive material (or gas-filled tubes) and the cost of special NRC licenses and special handling, you tend to pay quite a bit more for a watch with a real tritium dial. Of course, the big advantage of tritium systems is that they need no “charging”, so they will always glow and be legible in the dark, for a virtually unlimited number of hours. Watch companies that use tritium and skip the permit can end up paying heavy fines. This is a serious issue, and the permit is costly. On the other hand, the NRC (Nuclear Regulatory Commission) in the USA will not allow anyone to import tritium-based dials, or any watches that use tritium paint or gas, without a special NRC permit to import and handle radioactive materials. This technology has been tested and deemed to be quite safe, as the amounts of radioactive material are generally small. Thus, the advantage of any tritium dials is that they do not need to be exposed to a bright light to be “charged”: they just glow. More modern systems use Tritium filled tubes, which glow because they contain radioactive gas: the radioactive gas will typically have a half-life of 20-30 years. Radioactive Radium or Tritium-based luminous: Radium was used in older dials from the 1950’s and 1960’s, but it was fairly unstable and would lose its photoluminescence after a number of years, then decay and release radon (a dangerous carcinogenic gas).It also requires some compromise with the dial design, as the dial needs to be semi-transparent for it the panel to light up the whole dial. The Electroluminescent panel also makes the watch a little thicker and adds a level of complication. ( HowStuffWorks) So this system or similar systems work well, but typically need to be activated by pushing a “light” button, so you need two hands to turn on the light. By charging the primary coil of the transformer with a transistor that is switching on and off, the secondary coil rises to 150 volts or so. To produce the 100 to 200 volts, the 1:100 transformer is used. The watch has only a small 1.5-volt battery. When you apply 100 to 200 volts AC (alternating current) to the conductors, the phosphor energizes and begins emitting photons.Ĭreating the high voltage can be a problem in a wristwatch. Essentially, what you have is two conductors (a capacitor) with phosphor in between. As described in the Timex patent, you take a thin glass or plastic layer, coat it with a clear conductor, coat that with a very thin layer of phosphor, coat the phosphor with a thin plastic and then add another electrode. ![]() In an Indiglo watch, a very thin panel uses high voltage to energize phosphor atoms that produce light. Backlight systems like Timex Indiglo have improved a lot and generally work very well.This works by a special phosphor-based paint, which absorbs light to “charge”, then glows for a period of time in the dark.Įach of the above options has advantages and disadvantages. Some form of non-radioactive, luminous, or “Superluminous” paint.Some form of Tritium material, usually in the form of paint containing radioactive tritium, or small glass tubes, filled with radioactive tritium gas.An example of this is Timex “Indiglo” watches. Some form of backlight, activated by pushing a button, or constantly active.There are three basic options, if you want to be able to read your watch easily at night: There are a lot of questions about luminous watch dials and hands, what works best, how “Traser” tubes work how Superluminous paint works and how long you should expect a watch to remain legible in the dark. ![]()
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