Photo Formulary PMK Shelf Life question.

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Some Dude - 03 May 2005 15:51 GMT

I realise that PMK is a one-shot developer but I am wondering if the
two A/B parts would oxidize/change so quickly that in 12 hours the Pyro
wouldn't be functioning well as a developer anymore.

Ex:

Made one liter of stock.

Used half yesterday, used half this morning. The end result yesterday
were beautiful pyro-stained negatives. The end result this morning
were very thin negatives of which about twelve images didn't come out
at all (clear).

I do understand what one-shot means but does PMK really "die" that
quickly? I mixed up one litre and filled it exactly to one litre with
very little air present in the container. Used distilled water, blah
blah...

Thoughts appreciated. Except from "Uranium Committee". Don't bother.

Thanks!
-sd

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Gregory Blank - 04 May 2005 01:17 GMT

> I realise that PMK is a one-shot developer but I am wondering if the
> two A/B parts would oxidize/change so quickly that in 12 hours the Pyro
[quoted text clipped - 18 lines]
> Thanks!
> -sd

Once the two parts A+B are mixed the life span is measured in hours "at
best" and more like minutes at worst.

I always "religiously " mix the A+B together just before use.

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John - 05 May 2005 05:20 GMT

>> I do understand what one-shot means but does PMK really "die" that
>> quickly?

Yep. Essentially there is no sulfite in PMK which, along with the high activity of
pyro, virtually guarantees oxidation in hours.I believe that pyro sucks oxygen nearly as
fast as sulfite once it's ionized by an alkali. That's why you see the color change in the
developer as soon as you add the metaborate. Some of the developer is immediately oxidized
by the oxygen in the water.

Regards,

John S. Douglas, Photographer - http://www.puresilver.org

Millions of men have lived to fight, build palaces and boundaries, shape destinies and
societies; but the most compelling force of all times has been the force of originality
and creation profoundly affecting the roots of human spirit.
Ansel Adams

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Fred Leif - 04 May 2005 01:32 GMT

From: http://www.digitaltruth.com/store/formulary_tech/01-5060.pdf

"Note: When PMK is mixed together, the solution will immediately proceed
through color changes from gray-green to pale amber. This is an important
visual check of solution activity. If there is no color change, something is
wrong. Recheck your stock solution for correct formulation. Use
immediately."

The above is from the instructions that Photographers Formulary includes
with the premixed PMK A & B Solutions. Note the last two words.

Yes, it really does not last long once it is mixed.

>I realise that PMK is a one-shot developer but I am wondering if the
> two A/B parts would oxidize/change so quickly that in 12 hours the Pyro
[quoted text clipped - 18 lines]
> Thanks!
> -sd

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Some Dude - 06 May 2005 17:54 GMT

ok just checking....Thanks :)

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