The chemical you are looking for is called Benzatriazole. I inquired about
it on the list for using it as a fog restrainer for film. It is mainly
used for paper( I have no personel experience with) I take the liberty of
quoting from a post Larry Bullis send me:
>> I've heard of people adding benzotriazole (sp?) to the developer for this
>> kind of work.
>..any idea on concentration?..
In my experience especially with cyanotype but I believe it holds true
with other alt processes as well, is that base fog is something you
definitely must avoid if you are going to try to achieve a bright, full
scale print and enable a reasonable exposure time. So I would not rule
out using benzotriazole. I have used it from time to time; typically, in
my recording-film/pyrocatechin combination it can improve the printing
qualities of the negatives which tend to have a severe coffee-brown base
fog if the film is not really fresh.
Do be careful with it. It is an extremely powerful restrainer and
typically very small concentrations are used. According to my old
standby worn out copy of _Photographic Facts and Formulas_ (Wall and
Jordan, Amphoto -- am I the only one who uses this book?) the usual
concentration is 0.2 percent solution and only 1/2 ounce would typically
be used in one quart of solution. So you might use, over there where
measurements are actually rational, about 15ml./l. This would be a
(probably safe) minimum, and if it does not cut the fog, they suggest
successive half-ounce increases until the fog is gone. They also suggest
that additional exposure may be necessary to overcome the effect of the
restrainer in the image itself.
I got this from a section where they were talking about paper, which is
where this restrainer is typically used. I know it does work with film
as well, but unless you have enough of this old material you may not get
your tests done before the material has run out.
Good luck with it.
Skagit Valley College
> Hi Everyone,
> Quick question: I have two boxes of an old paper called Labaphot
> Agrando. I did a couple of test runs with it and as I expected it is a
> little fogged from aging. Now what i need to know is what is the
> chemical that will allow me to cut some of this back....to bring some
> contrast back into the paper. The paper has a great texture and the
> tones seem to be quite nice so far, I'd love to be able to use it. Any
> advice would be appreciated, thanks in advance.
"The Infrared Gallery"