This luminous paint contains a radium salt and some scintillating (fluorescing) substance, which makes it "glow in the dark". It was used until the 1950s on the hands and faces of clocks and watches, as well as in instruments and meters that had to be read in darkness. Its use was banned, mainly because of the danger for the workers handling it.
Radium and its decay products emit alpha-, beta- and gamma radiation. The activity of radium dials can be astonishingly high. Typical figures are 0.1 to 1µCi (1µCi = 1e-6 Curie = 37kBq)
Items with radium paint are frequently found on flea markets and in antiques shops. Two examples are shown in the pictures to the right.
Top: watch from the 1950s, radium paint marks on face and hands. Count rate at 5cm distance 400/min with front glass, 1000/min without.
Bottom: luminous badge from WW II, diameter ca. 6cm. Estimated activity in the radium paint 70kBq. Count rate at 5cm distance 20,000/min. (!)
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