Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Tim Ream on 12/01/2010 09:30:02

Title: How do glow in the dark coatings work?
Post by: Tim Ream on 12/01/2010 09:30:02

Tim Ream  asked the Naked Scientists:
   
Dear Naked Scientists,

Recently I bought a new chronograph watch and noticed that the glow-in-the-dark paint glowed brighter and longer with less light input.

How do the newer generations of glow-in-the-dark materials, such as on watches and trijicon night-sights, work on a molecular level?

Love the show (http://www.thenakedscientists.com/HTML/podcasts/), keep up the work!
 
Tim from California, U.S.

What do you think?

Title: How do glow in the dark coatings work?
Post by: Riki on 26/01/2010 22:13:11

Apparently the new watches use a radioactive isotope of hydrogen called tritium to make them glow.  Normally glow in the dark items need the phosphors to be charged, like using a light.  They then glow for a certain period afterwards.  The radioactive version, as in your watch, does not need an external source to charge it.

Tom Clancy also wrote an interesting book "Sum of all Fears" which details alternative uses of tritium.

Title: How do glow in the dark coatings work?
Post by: rosy on 27/01/2010 11:58:27

Old-style glow in the dark watches certainly used radioactive isotopes. I find it hard to believe it would be legal these days (not that an alpha emitter in a watch would be dangerous to the wearer, as long as the source is enclosed it's not, but I bet the rules are against it..). Do you have a reference for that assertion?

I would assume, infact, that the difference is just better (more energy absorbing/longer half-life) phosphors, which are molecules which are able to absorb energy from sunlight (typically in the UV part of the spectrum) and then release it slowly as lower-energy visible light.

Title: How do glow in the dark coatings work?
Post by: syhprum on 27/01/2010 14:08:25

As a boy (back in the thirties) I gleefully scraped some Radium type luminous paint from the dial of an old watch, I often wonder if I ingested any ?.

Title: How do glow in the dark coatings work?
Post by: yor_on on 30/01/2010 13:19:47

Simple test.
Close the curtains, does the sun still glows?

Title: How do glow in the dark coatings work?
Post by: syhprum on 30/01/2010 22:25:24

I don't think I would have ingested enough to make me glow like the frogs in the Springfield pools