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Undark
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<p>Undark was a trade name for <a href="/facts/Luminous_paint/BvrM87NX">luminous paint</a> made with a mixture of <a href="/facts/Radioactive/Ya6FVjt4">radioactive</a> <a href="/facts/Radium/VWo5gkzn">radium</a> and <a href="/facts/Zinc_sulfide/K8l5AF3K">zinc sulfide</a>, as produced by the <a href="/facts/United_States_Radium_Corporation/TVAHHBeA">U.S. Radium Corporation</a> between 1917 and 1926. The U.S. Radium Corporation was based in Orange, New Jersey, but was not the only radium-painting business in the United States. Other big names in the early 1900s include the Radium Dial Company and the Luminous Processes Inc. </p>