Updated 10 September 2026 · AQUATICO Watch Team
Tritium watch illumination fades gradually over years; it does not switch off on a fixed expiry date. The useful life of the glow depends on its starting output, the light-source design, its condition and how much brightness you need to read the watch. The movement has a separate service life.
This distinction matters when you see ‘20 years’ or ‘25 years’ in a watch description. Those statements should never be read as a promise of unchanged brightness for the entire period.
The 12.3-year half-life in plain English
Tritium's radioactive activity falls by half in approximately 12.3 years. mb-microtec describes this decay as the energy source behind its self-luminous technology. After one half-life, half the initial activity remains; after two, one quarter remains. mb-microtec technical explanation.
The following figures are calculations using a 12.32-year half-life. They describe remaining activity, not measured watch brightness or a readability guarantee.
| Years since the starting point | Calculated activity remaining |
|---|---|
| 0 | 100% |
| 5 | 75% |
| 10 | 57% |
| 12.32 | 50% |
| 15 | 43% |
| 20 | 32% |
| 25 | 25% |
Calculation: remaining fraction = 2 raised to the power of −years/12.32. The starting point must be defined consistently; purchasing a watch does not restart the decay of its light sources.
Does that mean half the brightness after 12 years?
The activity calculation is a helpful baseline, but it is not a complete prediction of a finished watch's visible performance. The light-emitting coating, optical construction and viewing conditions also matter. Do not treat the table as laboratory measurements of a particular AQUATICO watch.
Your practical threshold is personal. Someone checking a bedside watch with adapted eyes may accept a level of illumination that another wearer finds insufficient. A camera can make a dim dial look impressive through a longer exposure, so photographs are a poor substitute for a consistent viewing comparison.
Why do brands quote different lifespans?
Brands may refer to a design expectation, a lighting warranty or a period of usable visibility. For example, Luminox describes illumination lasting up to 25 years and separately states a lighting guarantee with conditions. Those are different claims, and neither is automatically an AQUATICO warranty. Luminox FAQ.
When comparing watches, ask exactly what a stated period means. Does the brand promise a minimum output? Is the statement about the tubes or the complete watch? Is normal gradual fading covered? A clear written answer is more valuable than the largest number on a product page.
Overnight fading and long-term fading are different
Tritium's long-term decline should not be confused with the short-term loss of a charge in conventional lume. A tritium watch does not need a fresh light exposure before each night. If your main frustration is finding that a watch is hard to read several hours after bedtime, judge candidates under that specific condition.
For your own records, compare the same watch in the same room, with the same viewing distance and similar dark adaptation. If using photographs, keep exposure settings fixed. Record the date. This is a practical observation routine, not a substitute for a professional light-output test.
When should you ask about service?
Ask when the watch no longer meets your reading needs, or when a sudden isolated change follows an impact. Gradual dimming across an older dial and one marker going dark abruptly are different observations; explain which one you see.
Before paying for work, request confirmation of parts availability and an itemised quote. A dimmer dial does not by itself tell you that the movement needs replacement. Conversely, bright tubes do not establish that the movement or seals are in good condition.
Choose a watch for the years ahead
Compare the 38mm AQUATICO Atlas Tritium if you prefer a compact case, or explore the wider tritium collection. Start with fit and dial readability, then ask about long-term support for your preferred model.
Frequently asked questions
Does tritium stop glowing after 25 years?
Not at a universal deadline. Activity continues to decline, and the remaining glow may or may not meet the wearer's needs.
Can sunlight restore old tritium?
No. Light exposure does not replenish the tritium inside a sealed source.
Will leaving the watch in a drawer preserve the glow?
It will not pause radioactive decay. Store the watch appropriately to protect its physical condition.
Does T100 have a different half-life?
No. The isotope's half-life is unchanged. The rating does not create a separate decay clock.