Undark (Radium Girls) advertisement, 1921, retouched

Undark was a trade name for

luminous paint Luminous paint or luminescent paint is paint that exhibits luminescence. In other words, it gives off Visible spectrum, visible light through fluorescence, phosphorescence, or radioluminescence. There are three types of luminous paints: fluoresc ...

made with a mixture of

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...

radium Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather t ...

and

zinc sulfide Zinc sulfide (or zinc sulphide) is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite. Although this mineral is usually black because of various i ...

, as produced by the U.S. Radium Corporation between 1917 and 1938. It was used primarily in watch and clock dials. The people working in the industry who applied the radioactive paint became known as the

Radium Girls The Radium Girls were female factory workers who contracted radiation poisoning from painting watch dials with self-luminous paint. The incidents occurred at three different factories: one in Orange, New Jersey, beginning around 1917; one in Ott ...

, because many of them became ill and some died from exposure to the radiation emitted by the radium contained within the product. The product was the direct cause of

radium jaw Radium jaw, or radium necrosis, is a historic occupational disease brought on by the ingestion and subsequent absorption of radium into the bones of radium dial painters. It also affected those consuming radium-laden patent medicines. The symptom ...

in the dial painters. Undark was also available as a kit for general consumer use and marketed as glow-in-the-dark paint.

Similar products

Mixtures similar to Undark, consisting of radium and zinc sulphide were used by other companies. Trade names include: * ''Luna'' used by the

Radium Dial Company The Radium Dial Company was one of a few now defunct United States companies, along with the United States Radium Corporation, involved in the painting of clocks, watches and other instrument dials using radioluminescent paint containing radium. ...

, a division of Standard Chemical Company and * ''Marvelite'' used by Cold Light Manufacturing Company (a subsidiary of the Radium Company of Colorado)

External links

Roger Russel - Radium Dials

Damninteresting.com - Undark and the Radium Girls

Luminescence Radium Paints Brand name materials

Similar products

See also

Further reading

External links