Now, radium itself doesn’t glow, but its radiation can excite the electrons in a phosphorescent material like zinc sulphide, which then emits energy as light. This was the basis of Panerai’s glowing Radiomir paint, which it patented in 1916. Note the Italian for ‘patented’, Brevettato, as seen on this Radiomir 685 1938 re-edition. Across the Atlantic in America, meanwhile, and a slew of radium-based paint brands were springing up. Radium was the most expensive material by weight in the world at the time, and the demand was huge. Factories employed thousands of ladies to apply this glowing paint to many different products, including watch dials. When the girls left the factories at night, they themselves glowed. At the time, it was considered a perk.
Unfortunately, this lethal phenomenon wasn’t fully understood until Marie Curie committed her life—both figuratively and literally—to researching it. Curie in fact coined the term ‘radiation’ herself, from the Latin radius, meaning ‘ray’. What she eventually determined was that radioactive materials like radium emit beams of electromagnetic radiation from the decay of atomic nuclei. These rays are ionizing, which gives them the ability to strip electrons from atoms. The most powerful of these rays were known as gamma rays—the type the radium emitted.
The Panerai Radiomir 687 is a modern replication of the destructive effect of gamma radiation. What would have started out looking like the 685 when it was new has discoloured thanks to the endless bombardment of radiation from the radium-based paint. Radium has a half-life—the amount of time it takes for radioactivity to fall to half its original value—of 1,600 years; a single watch remains lethal for generations.
Imagine what that kind of destructive energy could do to a human, and in far larger doses. The ‘Radium Girls’, as the dial-painters were known, quickly started showing gruesome symptoms. First, their teeth would begin to rot from where they pointed the tips of their brushes in their mouths. The teeth could then be pulled out without resistance. Their gums then ulcerated and their jawbones crumbled. Their skin thinned, tearing easily. Eventually, their insides would haemorrhage, and they would die.
It wasn’t until the late 1930s that the surviving girls won their case against the companies that had inflicted the paint upon them. When investigators exhumed the body of a factory girl who had died five years earlier—whose cause of death had been recorded as syphilis—and found her still glowing, there was no questioning what had happened.