Sandy King (sanking@hubcap.clemson.edu)
Sun, 24 Jan 1999 13:08:31 -0400
>On Sun, 24 Jan 1999,Judy Seigel wrote:
>I forget which superproportional Sandy is using, but the term could
>possibly bear some clarification.... and I might stand corrected....
>
Putting aside for the moment questions regarding the specific efficacy of
reducers, the following types are.
1. Subtractive. These reducers should remove an equal amount of silver from
all densities and thus increase the density range of the negatives. They
are used to remove fog and improve negatives which have received too much
exposure.
2. Proportional. Remove from the negative an amount of silver which is
proportional to the original density. They are used to reduce excessive
density and contrast which result from overdevelopment.
3. Super-proportional. Remove a greater proportionate amount of silver from
the high densities than from the low. Their main use is to improve the
quality of overdeveloped negatives.
Reducers differ in that with some the reduction is permanent and can not be
reversed. Harmonizing type reducers (mainly super-proportional types) work
differently in that you completely bleach the image, then re-develop. This
allows you to increase or decrease overall contrast as necessary.
There are dozens of published formulas for all three types of reducers.
Before doing any work with reducers always make sure that it has been
washed thoroughly. Also, do some tests before working with an important
negative. Reducers tend to be somewhat unpredictable in use, especially the
super-proportional ones.
The reducer I used for the recent experiments is a super-proportional one.
The formula (I don't know the name) is,
potassium bichromate 8.0g
Hydochrloric acid 6.0cc
Potassium bromide 5.0g
Water to 1000ml
After bleaching, which takes 1-2 minutes, the negative is washed thoroughly
to remove any bichromate, then re-developed in a slow-acting developer
(D23, PMK). The removal of the bichromate can be accelerated by immersion
in a 2-3% sodium bisulfite solution after washing 2-3 minutes, then
returned to the wash for another 2-3 minutes.
Sandy King
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