At 10:53 AM 5/21/01 +0200, you wrote:
>Ronn Blankenship schreef:
>
> > At 10:55 PM 5/20/01 +0200, you wrote:
> > >As long as they don't 'glow' after dusk I don't mind. ;o) You know what I
> > >meant. Silly guy.
> > >
> > >Sonja
> >
> > How about if it causes a Geiger counter to click?
>
>Depends on the amount of clicks and the sensitivity of the Geiger counter I'd
>say. Wonder if there are still radio-active watches around. You know the older
>types of the ones that glow in the dark. The ones that glow in the dark using
>a radio active (phosphorous?) isotope to make them glow. :o)
Radium. They stopped using it because the people who hand-painted the dots
on the dial would lick the bristles of the small brushes they were using in
order to shape the bristles to a finer point, and thus ingest the
radium-containing paint.
Or tritium (radioactive hydrogen-3). Some watches are still available that
contain it. It is also used to make the glowing dots on gunsights to make
aiming easier in low-light conditions (although the glowing dots are also
visible to the bad guy who's shooting at you). Tritium has a 12-year
half-life, so self-luminous paint that contains it will fade faster than
that containing radium, which has a 1620-year half-life.
Both of those self-luminous paints contain a small amount of a radioactive
substance mixed with a chemical like zinc sulfide that glows when struck by
radiation. The regular "glow-in-the-dark" or "phosphorescent" paint is
made of a chemical that glows for a significant length of time after being
struck by photons of visible light, particularly
high-energy/short-wavelength light, including near-UV. The glow due to
phosphorescence fades over time, so a watch painted with that material will
shine brightly right after the lights are turned out, but be no longer
readable before morning, while the high-energy photons from the
radioisotope continually excite the chemicals in the self-luminous paint,
keeping it glowing continuously. Although the chemicals that glow in the
self-luminous paint are often phosphorescent to some extent with
visible/near-UV light also, so such a watch will also glow brightly right
after the lights are turned out and fade somewhat over the next half-hour
or so, until what you're seeing is mostly due to luminescence rather than
phosphorescence.
More than you probably wanted to know. Personally, I like the "Indiglo"
type that light up faintly at the touch of a button. And I have a laser
sight on my pistol. So I only glow after eating bananas* . . . ;-)
(*According to nutritionists, a good source of potassium.)
-- Ronn! :)
