Glow-in-the-dark paint—called lume— doesn't last forever. Eventually it will fade, and (in most cases) the owner will want to have it replaced.
The types of lume vary depending on the age of a watch. Early lume used radioactive radium, with tragic results. Later watches used less-deadly-but-still-hazardous tritium, and modern watches dispense with the radioactivity altogether. While the radioactive paints had the perk of glowing forever, even without a light source, the newer paints have impressive-enough longevity to make up for it.
Lume tends to dry up and flake off with age, so the restoration must begin by removing the rest of it—luckily, it dissolves in water. The new lume is mixed and "painted" onto the bottom of the watch hand with an oiler or a sharpened piece of pegwood, and the cavities in the hand will hold it in place nicely. From the top, it forms a clean, flat surface.
Normally, this would be delicate and fiddly (the hands are quite small), but compared to most of our projects in watchmaking, it's a walk in the park.
A trickier aspect of lume is when the owner does not want it replaced. Some vintage watches command a high price for authenticity, and radium/tritium lumes acquire a creamy color as the age. This patina is highly desirable among vintage collectors, but it's also impossibly fragile. Great care must be exercised when working on any vintage watch, but especially around the hands.
We haven't done any casing yet, so that's still a skill to be learned.
Watchmaking student at the Lititz Watch Technicum, formerly a radio and TV newswriter in Chicago.