Video: Radium watch dial, Timex

"It must have sounded like a good job at the time, painting luminous numbers onto the faces of clocks. In old photographs, the teen-age girls who worked at the Radium Dial Company 's factory in Ottawa, Ill., during the 1920's look happy, and they also look prosperous, since the pay was high. The work was even challenging, since it took skill to fill in the outlined numbers properly. The better to master this intricately detailed painting, the workers were encouraged to lick their brushes. [...]