WATCH RITUAL
Guides / Materials
Materials · 2 min read

Watch lume explained: Super-LumiNova, tritium and how it glows.

Most modern watch lume is a photoluminescent pigment, usually Super-LumiNova, that absorbs light and releases it as a glow. It is brightest just after exposure and fades over hours. Tritium, used on some vintage and tool watches, glows on its own without charging.

By Sebastian Bassolino, Editor · Updated October 17, 2026

How modern lume works.

Super-LumiNova and similar pigments are based on strontium aluminate. They store energy from light and release it slowly as visible glow. A few minutes of strong light, especially sunlight or a UV torch, charges them fully. The glow is brightest in the first minutes and then fades gradually through the night.

Common types and grades.

TypeGlow colourNotes
Super-LumiNova C3GreenUsually the brightest initial glow; slightly green-tinted in daylight
Super-LumiNova BGW9Blue-whiteLooks white in daylight; popular on clean dials
Super-LumiNova C1Blue-greenOften used for a whiter daylight appearance
Seiko LumiBriteGreen or blueSeiko’s own photoluminescent lume
Tritium gas tubesVariousSelf-powered glass tubes; constant glow for years
Old tritium paintFaded creamUsed on vintage watches; no longer glows after decades

Tritium and the radioactive past.

Early luminous dials used radium, which is radioactive and was phased out by the 1960s. Tritium paint replaced it, glowing on its own but fading as the tritium decays (its half-life is about 12 years); vintage tritium dials often have a warm cream patina. Some modern tool watches use sealed tritium gas tubes, which glow continuously for years without charging.

Getting the best glow.

  • Charge under strong light before dark: sunlight, a bright lamp or a UV torch.
  • Larger hands and markers with thick application glow longer.
  • A dark dial makes lume look brighter at night; a white dial makes it less visible in daylight.

Watches with strong lume.

A few good questions.

Is watch lume radioactive?

Modern photoluminescent lume such as Super-LumiNova is not radioactive. Old radium dials were, and tritium is mildly radioactive but sealed in modern tubes.

Which Super-LumiNova is brightest?

C3 usually gives the brightest initial glow. BGW9 is popular for its white daylight colour and blue glow.

Why does my watch lume fade at night?

Photoluminescent lume releases stored light gradually; it is brightest after charging and fades over hours. Recharge it in strong light.

How we write guides: we explain watchmaking from manufacturer documentation and published standards, and say plainly where numbers vary by brand or movement. Our approach.