Proper dilution of Kodak Rapid Fixer Solution A ???

Hi,

I need to dilute Kodak Rapid Fixer solution A only (for fixing prints
that are to be toned) and am unsure as to the proper dilution. I see
one place on Kodak's web site that says 1:3 (which sounds correct for
film but not paper), another that says 1:7). Then again, I've
extrapolated from the instructions that come with the fixer (which
include instructions only for dilution with solution B) and my results
don't match either 1:3 or 1:7 (but I'm mathematically challenged).

What is the magic ratio?

"Phil Glaser" wrote in message
om...
Hi,

I need to dilute Kodak Rapid Fixer solution A only (for
fixing prints
that are to be toned) and am unsure as to the proper
dilution. I see
one place on Kodak's web site that says 1:3 (which sounds
correct for
film but not paper), another that says 1:7). Then again,
I've
extrapolated from the instructions that come with the
fixer (which
include instructions only for dilution with solution B)
and my results
don't match either 1:3 or 1:7 (but I'm mathematically
challenged).

What is the magic ratio?

Rapid fixers can cause bleaching of fine grain silver
images typical of paper prints if the paper is left in them
longer than necessary for fixing. For that reason most
manufacturers of "rapid" fixers give two dilutions: one for
film and another for paper. For film, which is more
difficult to fix than paper, the usual dilution is 1:3 or
1:4, for paper the dilution is 1:7. The fixing time is about
doubled when paper dilution is used. If you are a careful
worker in the darkroom you can use film strength rapid fixer
for paper, but beware that the fixing time will be between
30 seconds and 2 minutes, depending on the paper. When rapid
fixer is used in a neutral form it does not bleach so the
whole issue becomes moot. If no hardener is used the fixer
can be neutral. Agfa color fixer is neutral pH rapid fixer.
Also, Kodak Rapid Fixer with Hardener, can be used without
the hardener added. The pH is less acid this way (but I
don't know what it is) so there is less chance of bleaching.
With alum hardener the pH of a fixing bath is around 4.5.
Hardener is not needed by many of today's films and
papers which have much harder emulsions than those of some
years ago. The hardener prevents excessive swelling of the
gelatin in the fixing bath and wash. For emulsions that are
soft and swell excessively the presence of a hardener can
actually decrease fixing time by shortening the diffusion
path fresh fixer must take to get into the emulsion and
fixer reaction products must take to leave it.


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Richard Knoppow
Los Angeles, CA, USA