I use stop bath one shot for film. Some people use indicator
stop bath which changes colour when the pH gets too high.
This is a really good idea if you intend to re-use stop bath.
Indicator stop is also valuable for giving you an idea how
long your stop bath will last in a printing session. (This can
be quite a long time with RC papers, but may be a surprisingly
short time with fibre based paper.) I generally use white vinegar
with a 1+3 dilution. Some people don't like the smell of
vinegar/acetic acid and use a stop bath made from citric acid
instead. Ilford sells a citric acid based stop.  Other people
use a couple of quick changes of water instead of stop bath for film.

The safest way to re-use fixer is the two bath method. Make up
two bottles of fixer and mark them "1st" and "2nd". Fix for
half the normal time in the first bath, pour it back in the
bottle and then fix for the remaining time in the second bath.

You can determine fixing times by soaking a scrap of film in
water for a few minutes and then putting it in the fixer.
Normal fixing time should be at least three times as long as
it takes film to clear in fresh fixer. "Clearing" means that
the film no longer looks milky.

You can check for fixer exhaustion by examining the film after
the first fixing bath. It is safe to examine film in the light
at this point. If the film still looks slightly milky, the fixer
is exhausted. Dispose of the first bath, use the second bath as
your new first bath, and use fresh fixer for your new second bath.
After you have gone through several cycles you should replace
both baths.

To give you an example of how this works: I use Kodak Fixer
for film which I make up in a gallon jug. I have two bottles
which each contain a little over 600 ml. My normal fixing time
for hard to fix films like Tri-X and TMX is 12 minutes, for other
films it is 10 minutes. The fresh first bath usually lasts for
10-14 films, and the later first baths which were former second
baths last for 6-8 films. After I have finished the gallon,
I start with both baths fresh. This gives around 40 or so films per
gallon. If you use rapid fixer, your fixing times will be only about
half as long and the baths may last somewhat longer.

Rapid fixer (ammonium thiosulphate) is supposed to be better than
Sodium Thiosulphate based fixers such as Kodak Fixer (powder)/F5
for fixing modern films. I like Kodak Fixer anyway because I've found
that my films tend to dry flatter when I use it. This is not a
universal experience, some people find it makes their films curlier.

Rapid fixer is probably quite safe to use with a single bath
provided that you do not exceed the recommended number of films
per litre and you check the clearing time when you get anywhere
close to the rated capacity. If you chose to use the sodium
thiosulphate fixer, you should use the two bath method.
You should always have separate lots of fixer for film and paper.

Ilford's pdf file on their rapid fixer is good to read:

<http://www.ilford.com/html/us_english/pdf/Rapid_fixer.pdf>

Peter.

hey narke-

peter gave all info neccesary - good plan.
i do a similar thing.  it works quite well and economically also.
efficient i guess, would be the word.

anyway -
there is also a product to check if fixer is blown or not.  it's fairly
reliable, in my experience, although i don't use it too often anymore.  you
simply drop a couple of drops into the fixer solution and if it turns white,
the fixer's blown.  if it stays clear, you're still ok.   it's pretty cheap
and a bottle will last you nearly forever.

-c.

Indicator type stop bath can be used until the color changes. If your stop bath
is not an indicator type, then you need to check its pH regularly and cease
using it when the pH reaches about 6.  Personally, I use a water bath and an
alkaline fixer.  The many advantages of this have been discussed elsewhere in
this newsgroup.

Kodak F-5 fixer is an acid type hardening fixer.  It is not suitable for use
with prints that you intend to tone afterwards.  Fixer can be used and tested
with HypoChek, a product that tells you when the fixer is no longer usable.  A
homebrewed version of this can be found in Anchell, The Darkroom Cookbook, 1st
Ed., formula 89:

Water            80 ml
Potassium Iodide    5.0 grams
Water to make         100 ml.

Many of us here prefer using a neutral rinse followed by two alkaline fixer
baths for both film and paper.  This has proved to be an effective procedure for
ensuring complete fixation.

Francis A. Miniter

 Stop bath is not worth saving although it will last. Stick
you fingers into it. If it feels "sticky" its still acid. If
not its neutralized.
 F-5 is the same as packaged Kodak Fixer. The life is
several months in a bottle. Capacity depends on many
factors. For archival fixing the capacity of a single bath
is very small, no more than 10 8x10 sheets of printing paper
per _gallon_ according to Ilford. This capacity can be
increased by around ten times by using two successive baths
and even more if a wash aid is used before washing.
  While there are several tests for fixer baths the best
method is to test the fixed out material for residual silver
halide. The test is a simple one. A test solution is made up
of either Sodium sulfide (not sulfite) or Kodak Rapid
Selenium Toner diluted 1:9. The toner test works only when
the paper or film has been well washed. For testing the film
or paper must be wet but surface moisture should be blotted
off.
 A drop or two of the test solution is placed in a clear
area of the print or film and allowed to stand for two
minutes. It is then rinsed off and the paper or film
examined for any stain. Hold film against a white surface to
make any staining show up more. Completely fixed film or
paper will show no stain.
  Other tests for fixing baths are: A Potassium iodide
solution. If there is much dissolved halide in the fixer it
will combine with the iodide test solution to form insoluble
silver iodide which will precipitate in the form of a cream
colored cloud which does not recombine after shaking. The
amount of dissolved silver necessary to make the reaction
depends on the dilution of the test solution. A simpler test
is to measure the clearing time of film. Soak a scrap of
film in water for two or three minutes. The immerse it in
_fresh_  fixer to be tested.  Measure the time it takes for
the film to become completely clear. Note this time.
periodically retest using the same kind of film. When the
clearing time doubles discard the fixer. For archival fixing
this is too insensitive.
  Again, the best test is the residual silver test since
that is measuring the actual effect of the fixer, not some
indirect factor.
  Kodak Residual Silver Test Solution ST-1
Water                        100.0 ml
Sodium Sulfide (anhydrous)     2.0 grams

This will keep in a filled bottle for about 3 months.

  The Iodide test for fixers is simple but the instructions
in the Kodak _Darkroom Data Guide_ appear to be in error.
This recommends testing the first bath the same way as a
single bath is tested. The first bath of a two bath fixer
should be capable of a much greater silver load than a
single bath. Perhaps this indicates the test is not
sensitive enough for archival fixing with a single bath.
  The formula is:
Kodak Fixer Test Solution FT-1
Water, at 80F (27C)            750.0 ml
Potassium Iodide               190.0 grams
Water to make                    1.0 liter

This is a lifetime supply. I recommend making up no more
than 100 ml at a time.

Testing a single bath fixer:
Take 5 drops of the test solution and add 5 drops of water.
The add 5 drops of fixer. If a yellow-white preciptate forms
and does not immediately disappear discard the fixer.

For a two bath system replace the first bath with the second
bath and replace the second bath with a fresh bath.
  This cycle can be repeated five times. The fifth time
replace both baths with fresh baths.
  This same system will work with Ammonium thiosulfate
(rapid fixer) also.
  Because a sulfite wash aid, like Kodak Hypo Clearing
Agent, will make some otherwise insoluble fixer reaction
products soluble it will further increase the capacity of a
fixing bath.