On 08/01/2012 21:03, Bramblestick wrote:
Just noticed this strange thing!

For the last 12 years, we've had an aneroid barometer hanging in the
hall - it's probably 1930's by the look of it, and the top half of the
dial is printed in black text, and the bottom in red. I've just noticed
the the bottom half has disappeared! If you look at it from an oblique
angle, you can see the print, but it has faded to nothing!. The device
is in a really dark nook, getting no natural light, and for at least the
last 5 years the area is lit 24/7 by a lamp on a bureau - some 18" away
(Philips compact fluorescent for the last 3 years or so). The lamp has a
fabric shade, and the barometer's dial has a glass cover. It's not
something that I look at in detail every day - I've got the internet for
the weather ;-), but I know that I calibrated it a couple of years ago &
didn't notice any problem..

Any insight?

Cheers, Bramblestick

Not quite sure but red in past years was prone to fading, modern paints
are better but as your item was painted way back I would have expected
some fading, now linked to fluorescent rays there maybe an accelerator
in there somewhere and at 18" away and probably some heat damage over a
long period.
Red in hair dyes even today is the most prone to colour fade. red cars
in the 70s 80s used to fade quite quickly as well.

So I think red will fade but something has accelerated it and I suspect
the fluorescent light.