More lume talk

I have a little 50's watch where you can charge the hell out of the tiny bit of lume and watch it fade out in about two seconds. I sort of want it repainted, but luckily I've come to my senses and remembered that it is a gimmick that is never used in normal life.

That's paint with tritium then, no? By hitting it with a torch you "mimic" the excitation that the phosphorus paint would experience in the presence of radiation from the tritium but once you turn I off that's it.

If I had that repainted I'd probably use modern Super Luminova of some kind.

In my experience there is little difference between 20y old and new Super Luminova. That said there is a difference between "types" of Super Luminova in my experience and the "same" watch may get "upgrades" during service.

This watch is as new as it gets, so no age related deterioration, and when you hit it with a torch the the minute ring glows green while the hands and dial glow blue (impossible for me to caputure in image). You'll have to believe me.

When you turn the torch off it looks like this

which is to say a nice even turquoise glow. But after a short while it goes like this

Which shows that the "blue glowing"-lume is much weaker in the long term than the "green glowing". Indeed the lume on this one is not very good 😑 and yet half the marketing pics show it on full display.

I think those variations are what matter most when it comes to lume strength.

Don't blame you ,it's nice to have but not a necessity, especially since people use their mobile phones now

Thanks for the info,mine does stay bright for quite a while

I honestly never thought of that. I guess it is? I didn't specify but I mean it goes totally dark, invisible in pitch black, right before your eyes.

So with modern paint, one is or is not diminishing longevity by excessively saturating the stuff with bright light?

Yes that is expected for old tritium. I know that a nice way to see fallen off paint on expensive vintage watches is by using UV torches. They go entirely dark very, very quickly once it is turned off.

The phosphorous inside paint, which as far as I am aware is responsible for the emittance of visible light, does not degrade or at least not nearly as fast as the radioactive materials. As you can see it still has the potential to glow and that is after years of bombardement with elemetromagnetic radiation from tritium. Old paint simply doesn't have the ability to store energy or rather charge itself (the tritium is the energy storage). So it's like one of them old batteries.

On the other hand modern paint does have that ability (like rechargeable ones in cars or modern devices) and that's why it can glow through the night after being exposed to the sun. The deterioration in its ability to glow will likely not be greater than with tritium. In other words it will probably glow nicely for decades. I don't know how much its ability to hold the charge will weaken but I doubt it will be noticeable too much.

Based on my observation, which seem to be supported by OP, the lume works very well 20y after if a high quality paint was applied. If it sucks then it's probably down the lume variant itself (see my comment above) rather than age or the amount of light it was exposed to.