Kodafix dilution for single use processing
Manny Bhuta
I need to occasionally develop B&W negatives to make unsharp masks. I
have been using HC-110 (1:19), stop bath and Kodafix (1:3). I use my
Jobo processor to develop the films. So, with my low volume B&W work,
it is not worth keeping used fixer for later use. Now the question is:
"Do I need to dilute Kodafix 1:3 or would it be possible to dilute
further and fix for a longer time?"
--
Manny Bhuta
Randolph, NJ USA
John Stockdale
for films at half recommended strength. I fix for clearing time x2.
Using HP5+ and Neopan. No problems except:
I tried this recently with TMax 100 and it seemed to stop fixing
totally, or at least the pink stain stayed for ages. Had to resort to
Rapid Fixer to get it clear.
Dan Quinn
"Do I need to dilute Kodafix 1:3 or would it be possible to dilute
further and fix for a longer time?" Do the later.
I process one-shot. For fix that means a fix, which after it's one
use, is nearly exhausted. The fix starts fresh, zero silver content,
then ends it's use near saturation.
I've run tests with film and paper. Contrary to one authoritative
source and the conventional wisdom, I have found that very dilute fix
will function within a reasonable time.
Percents, %, and dilution ratios may be calculated but they are not
the starting point. The starting point is; so much silver, so much fix.
Worse case is the unexposed film or print. They both leave all the
silver for the fix.
Kodafix, according to Kodak, will fix 32 8x10s per liter of work-
ing film strength fix. Those 8x10s are likely an "average" mix; more
or less exposed. So, according to Kodak 8ml of concentrate will fix
an "average" 8x10.
For example, I have found that 15gr of sodium thiosulfate anhydrous
will clear with a little margine, one roll of unexposed 120 Pan F. For
paper, 8x10 DW FB, 6gr of the same will do.
I'd sugget you run a test or two. Start with 16ml of concentrate if
you are processing 8x10s. Use the lfp, least fluid practical, in order to
maintain as high a concentration as possible. 125ml may do. 250ml may be
more practical. Fix for 7min with constant agitation.
Use the iodide test on the fix. To 10ml of fix in a vial or test
tube, add iodide one drop at a time. If or when a precipitate forms,
stir. I use a glass rod. Add iodide untill clearing no longer
occurs. Make note. A few drops margine should suffice. Dan
Richard Knoppow
"Dan Quinn" <dan.c...@att.net> wrote in message
news:b379902d.03032...@posting.google.com...
Have you tested the fixed film for residual silver? Film
can be clear and still contain halides which are not fully
converted to a water soluble form. The sodium sulfide or
KRST test will indicate the presense of the halide by
staining it. KRST works only on washed film or paper, it
fails if there is much hypo present. Neither test should
leave any stain.
The capacity of a single fixing bath to fix completely is
surprizingly limited, much more so than the Kodak numbers
suggest. Two bath systems considerably extend the capacity,
by four to ten times. This is probably not important where
the fixer is used one-shot. A little known feature of
sulfite wash aids is that they also remove some fixer
reaction products which tends to insure complete fixing.
Using the residual silver test on the film or paper is a
better way of determining if fixing is complete than testing
the fixer for silver content. It should show if diluted
Kodafix or other concentrate is working.
--
---
Richard Knoppow
Los Angeles, CA, USA
dick...@ix.netcom.com
Dan Quinn
"KRST works only on washed film or paper..." Also the sulfide.
The sulfide and KRST tests should only be carried out on fully proc-
essed film or paper. Any fixer left in the material may, I might
say, should contain silver.
"Neither test should leave any stain." A post application wash
should be done. Both tests leave some of them selfs behind; silver
nitrate/acetic acid or sodium sulfide.
"The capacity of a single fixing bath to fix completely is
surprizingly limited..." After loading some with silver,
following prints are at once exposed to a somewhat spent fix.
"..where the fixer is used one-shot." With zero silver at start,
a single bath one-shot fix should be more spareing than a single
bath multi-shot.
"Using the residual silver test on the film or paper.." I'd say,
"Testing for residual silver, using sulfide or KRST,..."
"..testing the fixer for silver content." Just the MORE or less,
or, more or LESS, standard test for fixer exhaustion.
I'd add that I have more confidence in thiosulfate as an
extractor of silver to archival levels than yourself. My only
impediment in it's use as an at home test for exceedingly low
levels of silver is a proceedure for detecting quantitatively
the levels expected from a post process fixing. Dan