> On Tue, 30 Dec 1997, Wayde Allen wrote:
>
> > > base-fog. Are there any chemicals which I can use to reduce this fog
> > > (something you can add to your developper, I was thinking of using D76 to
> > > start with).
> >
> > I've heard of people adding benzotriazole (sp?) to the developer for this
> > kind of work.
>
> ..any idea on concentration?..
No not really. Working with old films and papers is mostly done by trial
and error. I imagine that the concentrations recomended in the Darkroom
Cookbook would be a reasonable place to start. The real question is
whether or not you actually need to worry about the increased base fog?
For what its worth, I have developed several rolls of film that had been
exposed 15 to 20 years prior, and had fairly decent results without adding
any kind of restrainer. I've also tinkered with a few old glass plates
that I found in the back of my lab. These were about 20 years old, and
still gave useable images. I've never tried adding a restrainer, only
heard about people doing it.
I can offer the following quote from the Darkroom Cookbook:
Restrainers:
------------
Restrainers are necessary to prevent excess fog. With film developers
this means primarily chemical fog. With paper developers restrainers
are used to retard both chemical and safelight fog.
Restrainers should be used sparingly in film developers. Some photo
chemists recommend they not be used at all. According to Bill Troop,
"A film developer should not need to use a restrainer - if it does then
the alkali is too strong." Even so, most film-developing formulas rely
on restrainers, partly to prevent fog and partly as "insurance" against
errors in formulation.
Whereas a degree of base fog is permissible in a negative, no amount of
fog, which would show up as gray highlights, is acceptable in paper.
For this reason, paper developers always require restainer, often in a
significant amount.
> > > I also assume that the speed will be roughly doubled due
> > > to it's age.
> >
> > I'm not sure why you'd assume this? I suppose it is possible, but the
> > first and possibly the second plate will probably best be tests.
>
> ..based on experience with aged polaroids (both coluour and B&W) I have
> used in the passed, but I may well be compairing completly different
> things...
Hard to say. Like I said before, I think you'll need to simply sacrifice
the first plate as a test to see how these work. I think I'd start at the
plates rated speed, develop normally, and see what you get. You'd then
have an idea whether or not you'd need a restrainer, and how to adjust
your exposure. Hopefully applying the corrections to the second plate
will give you close what you want. I tend to think that working with
outdated material is simply a trial and error proposition.
Happy New Year!!!
- Wayde
(wallen@boulder.nist.gov)