Saudi Luxury / Watch basics
Watch lume: how watches glow and what to expect
Understand the three ways a watch lights up in the dark, so you can tell from a listing how readable it will be at night.
Most watch lume is a pigment that soaks up light and gives it back in the dark. It is brightest for the first few minutes after a strong charge, then fades steadily over the following hours. Some quartz watches use a battery-powered backlight instead, and a few use tritium tubes that glow without any charge.
Light-charged pigment
Almost every lumed mechanical watch uses this kind. Super-LumiNova is the best-known name, and some brands use their own: Seiko calls its version LumiBrite, and Rolex uses Chromalight, which glows blue, on watches such as the GMT-Master II 126710GRNR. Modern pigments like these are not radioactive, so they do not grow dimmer over the years the way tritium does. Watch Codex explains how Super-LumiNova stores and releases light.
Two things matter more than the pigment’s name:
- How much lume is applied. Broad hands and large markers hold more pigment, so they glow brighter and longer than thin batons and dots.
- How well it was charged. A few minutes in strong sunlight charge it well; dim indoor light charges it weakly. A watch worn outdoors until sunset can stay readable for hours. One that spent the day under a sleeve may be faint by bedtime.
Colour plays a part too. Green lume usually looks brightest at first; blue tends to look softer.
Backlights
Quartz watches can light the dial electrically. The Timex Rugged Metal T466819J uses Timex’s Indiglo, which makes the whole dial glow, and Casio calls the LED light on many G-Shock models Super Illuminator. A backlight is bright at any hour, but only while you press the button, and it uses battery power.
Tritium tubes
A few watches use tiny sealed glass tubes of tritium gas. They glow all the time without charging, but tritium has a half-life of about 12 years, so an old tritium watch is dimmer than a new one.
Lume on vintage watches
Older watches used radioactive paint. Radium came first and gave way to tritium paint in the early 1960s. On Swiss dials, a small “T” on each side of “Swiss Made”, or “T < 25” printed with it, marks tritium paint. Most vintage tritium dials now glow faintly or not at all, and the paint often ages to cream or brown. Radium dials no longer glow either but remain radioactive, so leave opening one to a watchmaker. Collectors value original aged lume, and relumed hands or markers lower a vintage watch’s value.
What to look for
On an everyday watch, lume lets you read the time in a dark bedroom, car or cinema without pressing anything, so it is worth having even if you never dive. On a dive watch, look for lume on the hands, the hour markers and the zero marker of the bezel, so you can read elapsed time in the dark. The Omega Seamaster Diver 300M 210.90.42.20.01.001, for example, lists Super-LumiNova. On a dress watch, little or no lume is normal. For the rest of a diver’s checklist, see dive watch essentials.
Many listings leave the lume type blank, and a blank field does not mean the watch has no lume. A search for watches that list Super-LumiNova is a rough starting point.