[GravitasFailure]

Huh, it very well might. 90Sr is a beta emitter, which should excite phosphorescent materials nicely. Even better, it decays into Yttrium 90, and Yttrium Aluminate is also phosphorescent (it's also the YA in YAG lasers). Anyone have some spare 90Sr we can test this with?

[0culus]

Well, with a 28.8 years half life it should glow a while. BUT, the largest license exempt quantity one can get iirc is 0.1 uCi. Plus it’s a fission product so good luck making it yourself. :) I don’t recommend the radioactive Boy Scout approach.