Re: Roller for gum (was: Re: humidity in your darkroom........

Judy Seigel wrote:
>
> On Tue, 20 Jan 2004, Christina Z. Anderson wrote:
> > Blacklow p. 127.
> >
> > As far as humidity and temp, both increase dark reaction acording to many
> > authors--the insolubilizing of gum at a quicker rate, without exposure to
> > sun.
>

>
> Digression aside, there's also the fact that the meaning of the term "dark
> reaction" is, I believe, distorted above. Certainly my understanding of
> the term is that it means, once exposed to light, the reaction CONTINUES,
> even in the dark. which was why commercial photographers in early days who
> exposed a whole production line to sunlight and then developed all
> together at the end of the day, changed exposure progressively, giving
> less in the first hours to allow for "dark reaction."
>

Judy, our understandings of the dark reaction differ markedly; my
understanding (and here I have to agree with Blacklow) is that it is a
reaction that begins to occur as soon as the colloid and the dichromate
are mixed; that's why one should print right away after the coating
dries, because otherwise the dark reaction will fog the paper. The
reaction occurs with no exposure to light, hence its name "the dark
reaction."

Katharine
Received on Tue Jan 20 19:45:31 2004