That's absolutely normal for the majority of "glow-in-the-dark" watches. Most use a
zink selenide type GID goop which looses 90 percent of it's glow in just a few minutes.
Some watches use
Luminova or
Lumibrite (very similar but
Lumibrite is proprietary to
Seiko ) which have a different base entirely (
strontium aluminate - I looked it up /ubbthreads/images/graemlins/smile.gif ).
Both still require "charging" by exposure to light to get them to glow, but can hold a useful glow for several hours (a Lumibrite watch I have is useful for up to 7-8 hours when really charged up - difficult to do naturally in winter with long sleeves ...
A few watches use various radioactive substances to induce their phosphors to glow, the most common being
tritium. These either use a radioactive
tritium paint or the tiny hollow tubes lined with phosphors and filled with
tritium gas. (Those are MY favorites.)
Here's a pic of a couple of watches that use the tiny tritium vials, and don't need to be charged with light to glow. (Their glow is brighter, too, than most other GID materials, especially considering it takes years (half-life = 12.3 years) to get dim, not minutes ... )
(Left is a one day old civilian model that I don't like the looks of, wanna buy it? Right is a standard military watch (SandY 590). Both are made by the same company that makes the Luminox and a few other brands: mb-microtec (Swiss).
EDIT: The tritium vials in the Tracer keyrings, gunsites, compasses, emergency signs, military hardware, etc., etc., are ALL made by only one company: mb-microtec.
