I’m thinking it’s only a slow-decay phosphor if they claim a half-life of 24hrs. Ie, it won’t glow brightly and also fade quickly, but glow dimly but for a much longer time.
Years ago NPR had a story about US Radium in New Jersey, I found a similar story in Wikipedia Radium Girls
How would you think something like a watch dial would have such an impact on someones life.
here is what i know
it is cheap - it cannot be tritium
it does glow all night - maybe it would eventually fade but i have not tried to keep any in the dark for a week to see what it does
when i said it does not need light charging, that was for 12 hours
when i was a kid though, i had an old big ben westclox alarm clock, and you could see sparkles on its glowing hands, if you looked very closely
with good kid eyesight
i was told, maybe this is wrong, that those were gamma rays hitting the phosphor stuff, making it sparkle
i don;t really know
maybe the thing had some radium in the paint, this was the 60s, and it was really radium decay
i assumed when the new tape lasted all night, that it was this gamma hitting phenomenon
now i don;t really know
but i assume radium is also out, due to expense and legalities
maybe i will put some in a dark box for a week and see if that is still visible at night in the complete dark like the 12 hour glow
i will probably find that it does gradually fade out, it just takes more than 12 hours,
there are no gamma ray sparkles, and what i saw before may have been radium paint,