What is lume on a watch?
Luminous material on the hands and markers that glows in the dark, so you can read the time at night.
Types of lume
Early watches used radium paint, which glowed on its own but was radioactive and harmful to the people who painted it. Tritium replaced it from the 1960s; it's mildly radioactive, fades over about a decade, and often ages to a cream or brown colour collectors call patina.
Modern watches use strontium aluminate pigments such as Super-LumiNova, Seiko's LumiBrite and Rolex's blue Chromalight. They aren't radioactive: they charge from light and glow brightly at first, then fade over hours. Tritium gas tubes, sealed glass vials used by brands like Ball and Luminox, glow constantly for years without charging.
What makes lume good
Brightness and duration depend on the amount of material, its grade, and how much light it got. Thick, wide applications on dive watches glow longest. Green glows brightest to the eye; blue lasts longer for some formulas.
Questions
- Is watch lume radioactive?
- Modern Super-LumiNova and similar pigments aren't. Vintage watches can have tritium or radium lume, and tritium gas tubes are sealed low-level sources considered safe to wear.