From: Katharine Thayer (kthayer@pacifier.com)
Date: 08/18/03-06:15:12 AM Z
My thoughts this morning have ranged back to Ed Buffaloe's first gum
print, which he shared with us, which looked like what George Bernard
Shaw said about some of Steichen's gum prints: like they'd been taken in
a coal cellar at midnight. In other words, it was solid black. (His
second one was a great improvement.) I don't remember the exposure
details, but at the time, I thought the exposure was grossly overlong
for the lights he was using. It would have been impossible to tease out,
in any case, whether the lack of tones in the print was due to
overexposure or pigment stain due to overpigmentation (he was using lamp
black as I recall, which is one of those pigments that a little goes a
very long way); I don't remember what light he used but if he was using
a hot light, the heat could also easily have affected the gum given the
long exposure time.
It's possible that someone who really went out of their way to grossly
overexpose a print may end up "insolubilizing" the gum eventually,
although one would have to carefully eliminate all other variables in
order to be sure that's what really happened, rather than pigment stain
or overheating. But since the sensible way to print gum is to start
with a test print or test strip of some kind, the likelihood of a
reasonable gum printer overexposing to this extent in the normal course
of making gum prints should be very close to zero.
I get the feeling that some beginning gum printers, IME most often those
coming to gum from other alt-photo media, have the mistaken idea that if
they use a very heavy pigment load, expose overlong, and develop
accordingly, that they will be able to overcome gum's natural
limitations and achieve a long tonal scale, similar to platinum, say, in
one printing. But of course gum doesn't work that way at all. The only
way to achieve a long tonal scale in gum, with detail throughout the
long scale, is with multiple printings. The pigment concentration and
exposure that work best for laying down dense darks are very different
from the pigment concentration and exposure that work best to achieve
subtle highlight detail; if you try to get both in one printing you will
end up sacrificing either density or subtlety. The challenge of printing
gum is to learn to balance that tradeoff with each printing and make it
work for you.
Katharine
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