Where can I find information regarding the relationship between light
output of a neon tube (sign) and time, e.g over teh first year of
life, the neon tube light output might be expected to diminish by 20%

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Clarification of Question by bmilton-ga on 28 Feb 2006 14:14 PST

Very specifically: A client has a two year old neon sign. One letter
of the sign was broken and had to be replaced. The new neon is
significantly brighter than the old. Neon is nknown to deteriorate
over time, but how do I know if the fall-off witnessed is reasonable,
or indicates a problem in manufacture of either the original or the
replacement?

a graph or equation would be ideal!

Hi Bmilton

It depends in part on the materials used. For instance there is a comparison
of old standard sign green vs rare-earth-green neon tube phosphor here:
http://www.signweb.com/neon/cont/lifetimeb.htm

Interesting. I hadn't considered that. I've got a modern white light.
NOt certain if the fall-off is the same...