Luminescent Materials
Wristwatch luminescence began in the 1910s with radium-226-based paints. Three generations of materials have followed, each safer than the last and each leaving distinctive aesthetic signatures collectors learn to recognise.
Radium (c. 1913 – early 1960s)
Radium-226 mixed with a phosphor produced self-luminous dials. Highly radioactive and the cause of the 'Radium Girls' industrial-poisoning cases. Vintage radium dials remain mildly radioactive today and patinate to a creamy 'tropical' tone.
Tritium (c. 1960 – 1998)
Tritium (³H) replaced radium as a lower-risk beta emitter. Dials carry the 'T<25' or 'T SWISS T' marking. Modern tritium use is restricted to sealed gas tubes (tritium gas tubes, GTLS) used by brands such as Ball, Luminox and Marathon.
Super-LumiNova / Chromalight
Strontium aluminate-based phosphors developed by Nemoto & Co (Japan) and licensed in Switzerland as Super-LumiNova from 1993. Non-radioactive, charged by light. Rolex's Chromalight (introduced 2008) uses a similar chemistry tuned to a blue afterglow.
Key facts
- ▸Radium phased out in luxury watches by the early 1960s
- ▸Tritium replaced by Super-LumiNova industrially from 1998
- ▸Modern lume is non-radioactive (rechargeable phosphor)