Undark

Radium was discovered by Pierre and Marie Curie in December 1898.^[2] Years later, in 1902, an electrical engineer, William J. Hammer, discovered that you could mix radium and zinc into paint, exciting the zinc atoms and giving off a faint blue-green light. Before Undark had its name, luminous paint was first used commercially during World War I. Soldiers used the luminous paint on their instrument dials so they would not give away their position. After World War I, the paint was marketed toward consumers and trademarked as Undark.^[3] The U.S. Radium Corporation's radium-processing plant extracted and processed radium from carnotite ore. There, it was combined with other ingredients to create Undark.^[4]

Undark was used primarily in radium dials for watches and clocks. Undark was also used for compasses, weapon sights, speedometers, telephone mouthpieces, fish bait, locks, and many more articles of use.^[3] Undark was also available as a kit for general consumer use and marketed as glow-in-the-dark paint.

The people working in the industry who applied the radioactive paint became known as the Radium Girls^[5] 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, also referred to today as osteoradionecrosis. Radium jaw was the most common side effect because the painters were taught to put the bristles of the paintbrush in their lips to return it to a fine point after each stroke. There are also many accounts of the radium girls decorating themselves with the radioactive luminous paint.^[3] Even to this day, there is no cure for radioactive poisoning; the best treatments involve surgical interventions that may remove tissues, muscle, and even bone. The surgical process is called Sequestrectomy.^[6]

Between 1917 and 1926, radium-226 was improperly used and disposed of, contaminating the processing plant and surrounding areas in Orange, New Jersey. Radium-226 emits ionizing radiation and decays into radon gas.^[4] Radium-226 has a half-life of 1600 years before half of it would naturally decay. Radium was used to illuminate watches under safer practices until around 1968.^[7]

Mixtures similar to Undark, consisting of radium and zinc sulfide, were used by other companies. Trade names include:

• Luna, used by the Radium Dial Company, a division of Standard Chemical Company
• Marvelite, used by Cold Light Manufacturing Company (a subsidiary of the Radium Company of Colorado)

• Self-powered lighting