From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 03/07/01-06:59:31 AM Z
Bob Mazzullo wrote:
> Does anyone have any information of the shelf life of packaged
> darkroom chemistry? ...
I have found self life given by the manufacturers for HC-110, fixers,
and wash aids to be conservative.
Another thing to be concerned with and to test is the capacity of a
given working solution. I have usually found it to be less than
suggested by the manufacturer. For example, HC-110 seems to only really
have half the capacity suggested by Kodak when developing Tri-X film at
any concentration.
Because of the inconsistencies of replenishment and amount of exposed
emulsion to be developed, I determine capacity by finding the number of
negatives that can be processed "identically" before the development
time must be increased by 2% (this works out to keeping less than 6
additional seconds for a 5 minute development time). My capacity works
out to eight 4x5 sheets of Tri-X per litter of solution (2 shifts of 4
each in a divided tray) or two 8x10 sheets. A temperature compensating
timer should be used.
Note that very high concentrations may loose some of their ability while
working and too low concentrations may not have enough ability to do the
job. I have found the above capacity with concentrations from 16
ml/litter to 256 ml/litter, as well as a linear relationship of doubling
the concentration and halving the time to produce similar results.
And your question is certainly more on topic than legal rambling.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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