Radium dial
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Radium dials are watch, clock and other instrument dials painted with luminous paint containing radium-226 to produce radioluminescence. Radium dials were produced throughout most of the 20th century
A 1950s radium clock, exposed to ultraviolet light to increase luminescence
November 1917 ad for an Ingersoll "Radiolite" watch, one of the first watches mass marketed in the USA featuring a radium-illuminated dial.
Wristwatch produced for the US Army during World War II showing characteristic sandy deterioration of radium–zinc sulfide painted hands and numbers. Such a watch should not be opened due to the danger of inhalation of airborne particles.
Three radium dials and a radon detector are placed in a sealed plastic container. After 6 hours, the radon level was 446 pCi/L.
Undark
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Undark was a trade name for luminous paint made with a mixture of radioactive radium and zinc sulfide, as produced by the U.S. Radium Corporation between 1917 and 1926. The U.S. Radium Corporation was
Radium dial
…the NRC. The element was phased out of use by industry acting under its own volition as superior and safer luminous materials entered the marketplace. Undark produced by the United States Radium Corporation Luna produced by the Radium Dial Company…
Vial of Undark