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 best. Has anyone got any
recomendations? It is actually a little cubby hole for our cat to eat,
and in an ideal world I would love to find a neon cat shaped light.
Mad I know. Am I dreaming?
You can get blue 'neon' type lamps made specailly, at a price. Try google.
I think blue is argon, or mercury vapour actualy, neon is mainly orange.
Otherwise blue pygmy bulbs are readily available.
Or are they called 'borgs' these days (Bulbs of Restricted Growth) :-)
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 /
I don't think that's true about neon gas, neon just emits red.
If they want other colours they use [some other gas - mercury vapour?]
in the tube to make the uv and then add a fluorescent coating as
Normal white fluorescent tubes work that way as well.
It's got lots of lines, and certainly into the UV. It is used
for exciting UV phosphors, although the UV won't get through
ordinary glass construction neon lamps.
Mercury vapour has the problem that the vapour pressure varies
enormously with temperature, affecting both the light output and
the electrical characteristics. This isn't much use in cold-cathode
signage tubes which need to work well when cold and the mercury
vapour pressure is too low, or if increased for cold working,
it's too high if the tube warms up.
Older tubes are designed to work at 25C ambient with bulb wall at
40C and get dimmer if you move away from this in either direction.
(They can be made to order for different operating temperatures.)
Newer tubes, particularly compact fluorescents, contain an
amalgam which absorbs and releases mercury depending on its
temperature and this stablises the mercury vapour pressure inside
the tube for varying lamp temperatures, at least over a wider
range than for older fluorescent tubes. There is a delay whilst
the amalgam pellet adjusts to varying temperatures (which is why
compact fluorescents take a minute or so to reach full output).
This is fine for lamps which are on continuously, but not for
neon signage which often isn't, and has to run at exposed outdoor
There are actually two types of blue tubes, those which have a
phosphor coating, and those which don't.
Tubes with a phosphor coating work in almost the way you
describe (as do common-or-garden fluorescents). I say almost
because while the fill is almost entirely neon, neon doesn't
emit much UV at all, it's the trace mercury content which does that.
These tubes can be identified by the fact that they are opaque -
due to the phosphor coating.
The second type are clear, because they're just glass tubes with
argon in them. These emit blue light which is emitted directly
by the argon fill, with no phosphor being involved.
That's interesting, because at Magna we had bottles of Argon as used by
signage designers, mounted in a case, with 22kV (or something) clunked
onto each end when people walked past.
The "sparks" inside were definitely mauvey - I'd say more towards the
orange than the blue :-)
Martin Angove: http://www.tridwr.demon.co.uk /
Don't fight technology, live with it: http://www.livtech.co.uk /
Exacrly. Each gas has a characteristic spectrum, as described by
Fraunhofer: The color ypu preceive from a direct gas dicsharge lamp
depends on where te spectral lines are and how string they are. Neon is
predomniantly a red/orange emitter, with negligible UV, other inert
gases are different. By combining them you can get a variety of colors.
I suspect this is in fact what sign makers do.
Thanks. I knew it wsn't neon, but for the life of me...nonetheless all
such (direct emitting) tubes in the UK are comonly called 'neon'
lights. As opposed to 'fluoreescent lights', which of course in the USA
are called 'neon lights'
I think not actually. In the USA any fluorescent light is called a
'neon' light, and what you have descrbed is what we call fluorescent
lights. They are normally filled with mercuty vapiour and an inert
halodegn as well - I think argon normally. The tubes are caietd with
phosphors to re-emit UV in the visible spectrum.
Traditionally what WE call a 'neon light' is a pure discharge tube - not
a coated one - of which the original ones were red/orange and contained
neon. The sort used to make advertising signs. I don't know what gasess
are in the red, blue green and yellow ones, but I am pretty sure it
On 21 Nov 2003 07:09:50 -0800, firstname.lastname@example.org (Daniel) wrote:
Well you can just contact a signmaker and he will bend a glass tube
into the shape of a cat, fill it with neon (actually he won't - if you
want blue he will fill it with argon and add a microscopic amount of
mercury) and then seal it.
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