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

Re: Gum Humidity Question

On Sep 28, 2006, at 1:50 PM, Keith Gerling wrote:

"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...?"

Actually, when I said I kept it for a day, I meant a "work day". In
practice I seldom keep coated paper longer than eight hours, and yes, it
does start to have ill effects. I have used paper that has been kept
overnight, though. While it is still useful, it might need a little
"persuasion" to clear: brushing, spraying, etc. But I would have to say
that I see no anomalies with paper that has been kept for 6 hours.

Well, the dark reaction seems to keep eluding complete explication, and these observations from Judy and Keith, along with the fact that I could get no hardening of the gum after four hours in the dark in an 80% RH environment yesterday, even though I've seen total hardening of the gum layer in a similar period of time before in a similarly humid environment, suggest that we're far from understanding what's going on with the dark reaction. There's got to be other variables intervening, and the reason the graph I referred to doesn't explain all our observations, is that it was produced in a laboratory setting where all other variables could be controlled, so as not to muddy up the results.