U of S | Mailing List Archive | alt-photo-process-l | RE: Gum Humidity Question

RE: Gum Humidity Question

On Wed, 27 Sep 2006, Keith Gerling wrote:
... However the own thing that I *cannot* tolerate is lack of
registration, and paper tends to shrink and expand dramatically depending
upon humidity.  I have placed a small mist vaporizer in a box where I keep
my paper when I am working on it.  Before I coat any emulsion, the paper
goes in this box until it gets as relaxed as a piece of over-cooked
pappardelle.  Really really damp.  The emulsion goes on with no problems.
Then the paper goes into my tiny darkroom which is constantly dried by means
of a dehumidifier.  It turns bone dry quickly - and shrinks nearly a
centimeter in the process.  Then is goes BACK into this rainforest of a box
to get soggy again, expand, and I usually make the exposure while the paper
is still quite damp. This highly humid paper clears more consistently than
paper under drier conditions.  I've left coated paper in this box for a day
with no ill effects.
Keith, this is extremely impressive, if not absolutely voodoo-like. A few questions:

1. Would you explain the function of the damp-dry-damp cycle? I take it this is for multiple-coat gum. So that gets it to the same size each time, in a way just one dampening wouldn't? Do you "explain" this, or simply
appreciate it?

2. Do you also preshrink ?

3. I was surprised to read those very long times for the spontaneous whatever you want to call it graph discussed earlier. My own finding has been that keeping coated paper more than a few hours before exposure & development at even "normal" humidity is likely to cause development/stain/D-max "anomalies." I take it from your comment that you've found keeping problematic as well, so 24 hours wait without "ill effects" is noteworthy...?

4. You don't get emulsion clinging to negative when exposing "quite damp"?

PS. I did some tests years ago with additions of ammonia to the gum emulsion, then exposing after a day or even two days. Some of the effects were in fact interesting, but ultimately I decided more trouble than worth for whatever they were.

And PPS: I've not found glitches in gum emulsions on gelatin with 1 drop Kremer anti-foam per liter as Ryuji claims he has. In fact the coat seems about as easy & good natured as gum coating gets. That may be due to the other ingredients involved, mine being different from his -- or simply personal talent (or both).