radium paint on vintage watch dials

[R.J.Jackson@m.cc.utah.edu]

hello everyone,



the following are a few questions that i have been trying to answer for a while

now.  i seem to receive plausible explanations for individual questions, but

when all combined there are many conflicts.



context:

i collect wristwatches and, while all the dials no longer glow from alpha

particle stimulation, some respond for a short period to UV stimulation.  at

first i suspected that the luminous material was not original, but i tested

them all with a geiger counter.  all very hot.  



specific questions:



how exactly does phosphorescence work?



what role does Ag have in the phosphorescence of radium paint -- how does it

react with ZnS?



what ultimately causes radium paint to stop glowing?  (how does one account for

a claim that radium paint is still phosphorescing in a hermetically sealed

container after 50 years?)



is UV stimulation of a phosphor different than alpha particle stimulation?



and obviously my ultimate question: though none of the radium paint on my watch

dials glow on their own, why would some radium paint respond to UV stimulation

and some not respond at all?



best regards

rj





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