When a radium salt is mixed with a paste of zinc sulfide, the alpha radiation causes the zinc sulfide to glow, yielding a self-luminescent paint for watches, clocks, and instrument dials. From about 1913 up until the 1970s, several million radium dials, coated with a mixture of radium-226 and zinc sulfide, were manufactured.
Luminescent paint is paint that exhibits luminescence. In other words, it gives off visible light through fluorescence, phosphorescence, or radioluminescence. There are three types of luminous paints: fluorescent paint, phosphorescent paint and radioluminescent paint.
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