dichroic fog

[Tom Reed]

Here's a question for all you darkroom wizards.

What causes dichroic fog? and
How do I eliminate it?

Ok, that's 2 questions.

Thanks in advance

Tom R. tr...@omicron.csustan.edu

...Any resemblance between the above views and those of my
employer, my terminal, or the view out my window are purely
coincidental. Any resemblance between the above and my own views
is non-deterministic. The question of the existence of views in
the absence of anyone to hold them is left as an exercise for the
reader. The question of the existence of the reader is left as an
exercise for the second god coefficient. (A discussion of non-
orthogonal, non-integral polytheism is beyond the scope of this
article.)

[Richard Knoppow]

Tom Reed <tr...@reddog.csustan.edu> wrote:

Dichroic fog is usually caused by a very thin deposit of silver on
the surface of a negative. Dichroic litterally means "two colored"
the fog looks yellow by transmitted light and bluish by reflected
light. It has several causes. The silver can be coming out of a
developer that has been over used or which has a strong silver halide
solvent action but won't hold the silver in solution. T-Max is
supposed to do this with sheet film and the T-Max RS version is
modified to prevent it. Exhausted fixer is another source, especially
if a lot of developer has been carried over into it. I have also seen
the effect occasionally on very outdated film (Plus-X sheet film) for
reasons unknown to me. If you catch the fog while the film still wet
it can sometimes be removed by gentle swabbing with cotton balls.
Once dried a reducing bath is needed. The most common cause is
exhausted fixer. Not overusing fixer and using the two bath technique
will prevent most cases of dichroic fog.
---
Richard Knoppow
Los Angeles, Ca.
dick...@ix.netcom.com