95, radium has not been used in radioluminescent watches since 1968, or in clocks since 1978 (these dates are approximate). Radium Corporation was "Undark." Standard Chemical Company used the name "Luna" and the Cold Light Manufacturing Company, a subsidiary of the Radium Company of Colorado, made "Marvelite."Īccording to NCRP Report No. The brand name for the radioluminescent paint produced by U.S. In 1921, they changed their name to the U.S. They also got into the business of mining and producing radium. Their operations expanded tremendously when the United States entered World War I, and in 1917 they moved from Newark to Orange, New Jersey. It was founded in 1914 by Sabin von Sochocky and George Willis, both physicians. In the United States, the first company to produce radioluminescent paint was the Radium Luminous Material Corporation in Newark, New Jersey. Quoting Ross Mullner "there were so many radium painters in that country that it was common to recognize them on the streets even on the darkest nights because of the glow around them: their hair sparkled almost like a halo." But in Europe, especially Switzerland, things were different. Kunz and Charles Baskerville, a chemist, made their paint by mixing radium-barium carbonate with zinc sulfide and linseed oil.Īt that time, at least in the US, radioluminescent paint saw little application. Recognizing a good opportunity, a gemologist at Tiffany & Company, by the name of George Kunz, did patent it. In a case of bad judgment, he failed to patent the idea. The invention of radioluminescent paint can be attributed to William J Hammer who mixed radium with zinc sulfide (in 1902), and applied the paint to various items including watches and clock dials. That the radiation emitted by radium would cause various materials, such as zinc sulfide, to fluoresce was first recognized by Henri Becquerel. These decay products (Rn-222, Po-218, Pb-214, Bi-214, Po-214, Pb-210, Bi-210, and Po-210) emit alphas, betas and gamma rays.īy itself, radium in high enough concentrations will glow blue, a phenomenon first observed by Marie and Pierre Curie. Radium decays into a number of short lived decay products that can usually be expected to be present at, or close to, the same activity as the radium. Radium-226 is an alpha emitter with a 1600 year half-life. The greater the number of alpha or beta particles striking the crystals, and the greater the energy deposited in them, the brighter the light. When the activator deexcites, a photon of light is emitted. When the electrons reach an activator, it is left in an excited state. Once they have been promoted to the conduction band by the radiation, the electrons move to positively charged activator sites (e.g., copper, manganese, or silver impurities). Electrons in the valance band are fixed in place, but they become mobile in the conduction band. Some of the radiation energy deposited in the crystals promotes electrons from the valance band to the conduction band (these are different energy levels of electrons in the crystal). The light emitted by the paint is due to the radiation energy deposited in the luminescent crystals by alpha and/or beta particles. Zinc sulfide powder has been the most widely used luminescent material. Other radionuclides have also been used, e.g., strontium-90 (Sr-90) and carbon-14 (C-14). Today, tritium (H-3) and promethium-147 (Pm-147) are the radionuclides of choice. The first radioactive material to be used was radium-226 (Ra-226), but it hasn't been employed since the 1970s, at least in the U.S. Radioluminescent paint consists of a radioactive material mixed together with a luminescent crystalline powder. Paul Frame, Oak Ridge Associated Universities General Note: We are not interested in donations of additional radioluminescent items and we do not recommend that these sorts of things be collected by the general public.
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