This is not too bad but hypo fix will only tell you when the fixer has
failed not when it is almost ready to fail. The two bath method makes
this a bit safer but to be safer still just tally the number of rolls
you put through the fix. I used 100 rolls per gallon or 25 rolls per
liter, then replace Fix 1 with Fix 2 and mix a new Fix 2--if you are
using TMax films, make TWO tally marks for each foll of TMax you put
through your fixer. Note that with the reduced number of films I now
process I use a Unicolor Drum and use paper strength fixer one shot.

You can also test the films you just processed (on a leader or blank
frame removed from the rest of the roll, please!) using a hypo test
solution like Kodak HT-1 to make sure you are getting proper fixation.

The secret? that there is more than one methodology that will produce
great results, you just need to find a method that works for you based
on your circumstances and apply it consistently. i.e number of rolls you
process per month, type of film you use, equipment on hand or cheaply
available (I bought a spare Unidrum for US$5 at a swap meet not long ago
and already have a spare motor base), etc.

Mike

wrote:
I use the two fix method for black and white film. I keep checking on
my first bottle to be sure I pull it when the fixer exhausts, use hypo
check. The second fixer then becomes the first and I make up a new
second bottle of 1:4. I put the film in both for 2 minutes each or 4
minutes total.
Richard Knoppow wrote:
wrote in message
ps.com...
RE ... i'm wondering if i could just double the
fixing time and use the 1+9 instead of the 1+4 (as the
'strength'
of the 1+9 should be half that of the 1+4). would that
work?

If that were the case a 1:24 dilution, 1/5 film
strength, would
take 40 minutes; allowing for 8 minutes at 1:4. Such is
not the
case. I expect 8 to 10 minutes at 1:24. Exceptional films
might
take a little less or more. Conditions: 20ml of fresh A.
Thio.
concentrate in a solution volume of 500ml; agitation 1st
minute continuous and 15 seconds each there after.
One-shot use. Dan

A lot of chemical processes are not linear, for instance,
developer diluted to half strength does not take twice the
time to develop. However, the danger with highly diluted
fixer is that there may not be enough free thiosulfate ions
to complete the fixing process. The only way to tell is to
test for residual silver. The simplest test is to use a
dilute solution of Sodium Sulfide. Kodak also used to
recmmend Kodak Rapid Selenium Toner diluted 1 part to 9
parts water. However, this test will fail unless the film or
paper is well washed. Completely fixed film or paper should
not show any detectable stain from either test.
A clearing time test is useful for checking the condition
of a fixing bath. The old rule of thumb is that it takes
about double the clearing time for complete fixing. This
assumes the fixer is fresh enough to complete the fixing
process, which is progressive. If its not the emulsion will
not fix out completely in any length of time.
Clearing time tests should be done with a sample of the
film being fixed. The film should be soaked in water for a
few minutes since wetted emulsion fixes at a different rate
than dry film.
For archival purposes a two bath system is strongly
recommended. Its also more economical because the capacity
is from 4 to 10 times that of a single bath.
The use of a Sulfite wash aid will also increase
effective capacity because it releases some partially fixed
halide which would otherwise remain tightly bound to the
emulsion.


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Richard Knoppow
Los Angeles, CA, USA