Re: [Leica] "SureGuard" Photo Lacquer with UV inhibitor

["Dan Post" <dwpost@email.msn.com>]

Mary-
Dyes are subject to many factors that can cause fading. To answer your
question about UV- yes, glass blocks almost all UV, which is why lenses used
in UV photography use fused quartz lenses.
Dyes can be subject to 'dark fading'- they degrade in the absence of light.
I have negatives -Kodak VPS that are over 25 years old- and they are
suffering from some fading at this point- requiring significantly different
filtration than years past and it's not just a change in the paper
emulsions- the actual densities have diminished.
Heat can cause dyes to degrade which is why some photographers seal and
freeze their chromes. The inks, and dyes that are used in your prints are
probably non-metal based ( reduced toxicity) dyes and may well be affect by
air (actually the oxygen in it)
and the spray lacquer retards the action.
I once read that the metallic dyes in the old CIBACHROME process were the
most stable, but as I remember, they were horrible stinking solutions, and
quite toxic, and  I never used them much.
The prints stored in an album are probably under plastic as well which
retards the action of air on the dyes.
A  friend of mine had a textile chemist father, and he regaled us with tales
of trying to get dyes to mimic foliage during W.W.II to make camouflage nets
for tanks, and the quite strange things dyes were apt to do under varying
conditions- I guess that is why B&W photos will be our only true long term
solution to archiving images for the foreseeable future ( I am having doubts
about digital! I have floppies less than ten years old with massive numbers
of errors and bad sectors!)
A good bet would be to keep them from air, UV, and even bright artificial
light in order to get any reasonable permanence.
Cheers,
Dan
dwpost@msn.com