I don't think light has much to do with it, although it has never been
known to increase the permanence of anything;-)
Peroxides and other compounds coming out of certain types of paint, are
thousands to times more damaging to unprotected (i.e., untoned) silver
images than low levels of light and relatively high levels of humidity.
The lack of a true emulsion binder, i.e., gelatin, probably leaves the
metallic image unprotected. Ilford thought that the extra thickness of
gelatin on their Galerie paper helped make the paper somewhat more
permanent.
Here's what I'd do if I had time to experiment. Soak one half of a
kallitype print in a 2% aqueous sol. of gelatin (at 40C) a few minutes,
pull it out, let it dry, repeat the operation and harden the print
throroughly, with a final wash. This would change the nature of the print
per se, but it would be an interesting experiment.
>of the gold toned prints fade as yet. Perhaps I should make up some
what is interesting here is that the (expensive) gold in gold toned prints
has nothing to do with the fact that certain types of gold toned prints are
more permanent than untoned prints.
For a discussion on this, search the Conservation DistList archives on
Walter Henry's server --Stanford U. Instructions to get there are in my
(free) email newsletter _Aficionadeau_, available on request. You will also
find comments from the Image Permanence Institute about their special
microfilm toner, basically Kodak's Brown Toner, optimized for very little
change in color (hue) on microfilm emulsions. It offers excellent
protection and there are discussions on how to test the actual
effectiveness of various toning processes using commonly available
chemicals.
Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada
>test strips and run some test of my own. James M. Reilly "Care and
>Identification of 19th-Century Photographic Prints" says humidity is
>the main factor in the deterioration of prints and negatives.
>Bob Schramm
>WLSC