Re: ..Glass plate negatives..

Sandor Mathe (sandor.mathe@prior.ca)
Wed, 31 Dec 1997 09:06:35 -0500

Cor Breukel <cor@ruly46.medfac.leidenuniv.nl> wrote:
> 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?..

Note that the Darkroom cookbook is only talking about prints not
negatives. Fog on a print will destroy the highlights. Fog on a
negative will only require a slight increase in exposure during
printing. I would not add an antifog agent to the developer at all
for the negatives, but I would increase negative exposure to ensure
shadow detail is not lost in the fog. Which relates to the point
below:

> > > 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 secondplate 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...

Is there confusion here? Don't you mean speed is half? (ie. loses one
stop due to age).

The aged polaroids you mention are all positives right? The glass
plates are negatives. That may explain the difference.

Also think about the resulting contrast of the glass plate; old age
is likely to reduce the contrast (I would start with a 30% longer
than normal development [whatever "normal" is :-] ).

Sounds like fun.
Sandor Mathe -- sandor.mathe@prior.ca
(905) 670-1225 x333 -- FAX (905) 670-1344