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Old January 25th 04, 03:23 AM
Richard Knoppow
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Default the effects of aging on developers


"Robert J. Mathes" wrote in message
...
This question may be a bit of a handful. My question

concerns developers and
what are the effects on the print or film as the

developing agents age. I
know most, or I should say those that I use (powdered mix

D-76 and Dektol
and Selectol), say a shelf life of 2 months in a

tightly-stoppered dark
bottle is the limit and I follow that suggestion. But what

I would like to
know is what can be expected as the developing agents age.

Are the effects
uniform or do the highlights suffer first and shadow

detail second or vice
versa? I guess what I'm asking is if the component

developing agents
deteriorate at different rates. What happens if you go

beyond the suggested
shelf life. Is there some kind of compensation that can be

made for the
aging of the developing agents?
I'm hoping to get replies based on obviously more

knowledge, but also
the breath of experience that others have in processing

their own film and
prints. All replies will be welcomed. Thanks!

Stock, unused, D-76, Dektol, Selectol, etc., should have a
minimum life of about 6 months in a filled, sealed bottle.
In a partly filled bottle its less. Kodak gives 2 months,
but that is conservitive. If kept away from heat it should
last longer.
The main thing that happens to developer is oxidation. The
oxidation converts part of the sulfite to sulfate and can
oxidize the some of the developing agents. In the case of
Metol the oxidized forms are not active developing agents.
Hydroquinone oxidation products can be even more active than
the base form.
Packaged D-76 is buffered so there is little change in
activity with time. The original D-76 formula rises in
activity with time due to a slow reaction between the
hydroquinone and sulfite. This produces some sodium
hydroxide which raises the pH of the solution. Since the pH
is fairly low to begin with it has significant effect over a
period of perhaps a month. The buffered variety can handle
the hydroxide so its pH stays constant.
The same effect takes place in all hydroquinone developers
but Dektol, for instance, so much higher in pH than D-76
that the effect is masked and is of no significance.
M-Q developers, like Dektol and D-76, and most Phenidone
developers, are quite stable with time. Some developers, in
particular Amidol and some Pyro formulas, are not at all
stable and have a very short lifetime once exposed to air.
Pyro can be protected by additions of Sulfite and Metol,
but, if enough sulfite is added to give it long tray or tank
life, it looses its staining and tanning properties since
these are due to oxidation products and the sulfite prevents
them from forming.
I have had packaged D-76 stay good for a year after mixing
(I don't recommend this) and Dektol for rather longer than
the advertised time. Dektol starts out straw yellow and
becomes progressively browner as it ages. If its quite brown
toss it. Eventually, if they become oxidized enough,
hydroquinone developers will develop a very offensive odor.


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Richard Knoppow
Los Angeles, CA, USA