From: Sandy King (sanking@hubcap.clemson.edu)
Date: 02/12/01-04:11:44 AM Z
Pyrogallol by itself in an acidic solution has excellent shelf life. The
PMK stock solutions have excellent shelf life. If Hutchings says ten years
then it is probably that long. I kept a batch of PMK that I mixed from the
raw chemicals for over three years and the dilutedd developer was working
as good at the end as when fresh. I would not trust the pre-mixed kits to
have the same stability, though they may.
Rollo Pyro (ABC+) is a horse of another color because stock solution A
contains ascorbic acid. Ascorbic acid in combination with pyrogallol and
other reducing agents can accelerate oxidation and cause the developer to
go bad. I mentioned this possibility several years ago right after B&S
started distributing Rollo Pyro and noted it again in my article on Pyro
that appeared last year in Post Factory Photography. There have been a
number of posts on this list and on the newsgroups that suggest that Rollo
Pyro is indeed much less stable than PMK.
So how long will stock solution A of Rollo Pyro last before oxidation
causes it to go bad? I really don't know but personally would not trust it
for more than about three months. Perhaps others have experience which
indicates that it will last longer?
Sandy King
>Hi All,
>
>I've been back in the darkroom and developing with my standard setup for
>pyro. I mix 2 (separate) liters of A and B Rollo pyro developer. (I add
>the water to each solution, so I only have to mix the appropriate
>amounts of each into the beaker, pour it in and agitate.) The A mixture
>is only slightly amber for the first couple of weeks of shelf life, but
>turns quite deep amber over time.
>
>It has been about two or three months since my last film "run" and it
>seems my development is on the under side. Some of this film was shot
>while on the same trip as my last run, so I have some comparative film
>examples to check. I know I'm not being too scientific about this, but
>before assuming the worst about the A developer, can anyone comment on
>this? I know the stock solutions have excellent shelf life (Gordon
>Hutchings says ten years!), but what about my ready to use, separate
>solutions??? I assumed distilled water wouldn't alter the keeping
>properties of the developer.
>
>--
>Darryl Baird
This archive was generated by hypermail 2b30 : 03/06/01-04:55:39 PM Z CST