Digital BW, The Print

Richard,

>I'm starting to do prints for galleries. I'm using UT on Photorag.

>Is carbon on cotton all I need to ensure longevity? I was going to get the
>framer to use regular glass and not UV glass, as carbon on cotton is
>already UV-safe, right?

>When should sprays be used as an extra protective measure?

I suspect UV glass may offer some additional protection, probably more for
stopping the optical brighteners from burning out and turning yellow
(relatively) than for any indoor fading differences.  (Outdoor display is a
different issue.  Window glass absorbs the shortest and most damaging UV.)
I, personally, do not use UV glass.

With UT inks most the differences I see in fluorescent light fade testing
with the PremierArt spray (which has a UV blocking agent) relate a slight
advantage in less yellowing, not visually density. (This is unlike Epson
inks, where the spray makes a significant difference.)  The MIS UT
base/binder is light yellow.  I suspect it may have some UV absorbing
characteristics that make this difference.

The PremierArt-type sprays do give physical protection to the print that is
worthwhile.  This may be not only for protection from abrasion, but also
from humidity and possibly gas attack, at least to a limited extent.  I
suspect the roll of humidity is being very understated by all the fade test
procedures, which artificially dry the pigments even if the ambient air
humidity is controlled.  As with rusting iron, water seems to be a primary
carrier of both oxygen (the source of fading) and acids (the source of paper
deterioration).

The recent posting about the paper coatings yellowing from, probably, VOCs
is distressing.  Hopefully the glass and spray will protect the print.  I'm
also suspicious there are paper differences, but PR may be one of the most
sensitive.

Paul
www.PaulRoark.com 

For UT2 information, curves, and settings see:
http://home1.gte.net/res09aij/