The Natural Philosopher wrote:

Hello The

We have a glass block wall in our kitchen, and would
really like to put a blue light behind it. I am thinking
some sort of neon / fluorescent (sp?) light would look

TNP| I think blue is argon, or mercury vapour actualy, neon is
TNP| mainly orange.

This was explained recently on a kiddies program in a way that even I
kinda got the idea - it /is/ Neon. What happens is that Neon also
emits shedloads of ultra violet light. To get different colours, the
inside of the tube is coated with pigments that react in different
colours when energised by ultraviolet.

So the neon creates ultraviolet.
The UV transfers energy to the coating.
Coating glows and emits colour of choice.

--
Simon Avery, Dartmoor, UK
uk.d-i-y FAQ: http://www.diyfaq.org.uk/