Re: Kosar's Top 10 Gum Facts Redux-Dark Hardening

> Question 1: Are the terms dark hardening and dark reaction
> interchangeable?
> If I understand it correctly the term dark hardening is meant to describe
> when the exposed emulsion will not develop, rub or come off even with a
> brillo pad. And that this can be caused by among other things humidity.
>
Candace,
Dark reaction means no exposure--the gum hardens all over the paper without
the presence of light. In MT I could keep coated paper for, let's say, 3 or
4 days, and it would still be good. Down here in SC I have to expose my
paper fairly soon, like within an hour or two. I notice that if I do a large
batch of prints at once (16 one day) I will have a much harder time
developing the last several which have had a longer time to sit around. But
it is not enough of a problem to ruin prints.

All the humidity means is I am more careful to expose my paper soon after
coating. Then I have no problems, but if there were, it would just entail
longer development.

> Question 3: Has anyone come up with an optimum humidity level? From
> reading
> past posts it can actually be too low.

When I got used to printing down here with higher humidity, one week it was
reallly low (in the high 20's) and I about died--I had to keep wetting the
back of my paper to unshrink the paper enough to fit the registration of my
negatives. UGH. Between 35-55% seems OK by me, but it is not crucial--gum
is not affected by humidity like platinum, let's say, because there are
always alternatives short of a brillo pad.

<snip>
>I am not
> really able effect the humidity level other than to measure it (on Friday
> RH
> ran from 65-70% while I was printing). The only alternative is to lower
> my
> exposure time and I really would rather not waste a lot of sized paper
> only
> to find that changing the exposure is not an option; that the darks will
> still harden.

Lengthen your development time, lower dichromate concentration, use paper
right away, and use spray development would be my suggestions. You could
also use a hair dryer to dry the layer immediately upon coating (cool air)
and therefore quickly be able to expose.
Chris
Received on Mon Apr 11 06:52:37 2005