![]() The zinc sulfide could be mixed with other compounds to vary the color of the luminescent material. ![]() if the dial says “RA SWISS MADE RA” it’s packing RadiumĬombining radium with zinc sulfide fixed the lume and radiation problems: the radioactive properties of the radium triggered the phosphor in the zinc sulfide causing the material to lume and the amount of radium needed was not harmful to the wearer. However the glow of radium alone was not bright enough and the amount required to make it useful would emit too much harmful radiation. Radium had been known since it’s discovery in the late 1800’s and alone in proper doses it has some luminescent properties glowing blue. The early practice of applying lume to wrist watches, around the time of World War I, involved mixing the radioactive material radium with zinc sulfide. A variety of materials and chemicals have been used over the years to bring luminescence, or lume, to wrist watches, with the first solutions coming in the early 1900’s. ![]() The problem of legibility goes back as far as the history of the wristwatch itself and as technology has evolved, so has the legibility of our watches. When it comes to low (or no) light conditions, however, they can get tricky to read. Wrist watches are naturally quite useful for their intended functions, as we watch-nerds know, especially when you can see them.
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