Pyro PMK fixer

ader · Sep 26, 2004

Hello all,

I'm thinking of mixing up some pyro PMK film developer (easier than i first thought)in the next few weeks and was wondering about what fixer to use. With pyro developers the film is very sensitive to acid (hence no stop bath, only water). It needs to be a non-hardening fixer and the only non - hardening fixer i can get my hands on is Ilfofix II. The problem is this fixer contains sodium thiosulphate which to me sounds pretty acidic, but might be ok. I'd like to circumnaviagte any potential problems as money is rather tight. Any indications as to what fixer (or any other advice on pyro) would be most helpful. and alas I don't have Gordon Hutchings Pyro book at the minute, unfortunately, and can't get my hands on kodak 24 fixer....

thanks for any guidance or responses,

ade.

ann · Sep 27, 2004

sodium thiosulfate is hypo, or better know as fixer. I don't know what else is in the Ilforfix or if this fixer is the same as Ilford's Rapid fixer. We use Ilford's Rapid fixer for all film including PMK which contains ammonium thiosulfate but no hardner. As long as the ilforfix does not contain a hardner it would probably be ok. Perhaps Lee will chime in here and either confirm or correct my thoughts.

David A. Goldfarb · Sep 27, 2004

An alkaline fixer is ideal. You can get TF-4 from Photographer's Formulary, and Fine Art Photo Supply sells an alkaline fixer. You can also mix TF-2 or TF-3 from the formulas in Anchell's _Darkroom Cookbook_, and I think they are also in the _Film Developing Cookbook_.

lee · Sep 27, 2004

Chime Filter on...Ann has it correct. Kodak and Ilford's rapid fix is good and available. They are essentially the same fixer. Don't use the after fix soak. It creates too much stain in the base +fog areas and makes the neg more difficult to print through. Just fix and then into the wash.
Chime filter off,

lee\c

papagene · Sep 27, 2004

Ade,
I knew you would get some good answers here and they confirmed what I had already mentioned. Good luck with your developing.

gene

dancqu · Sep 28, 2004

ader said:
...this fixer contains sodium thiosulphate...

Use just that, sodium thiosulfate. I've seen it recommended when
a staining developer is used. For starters try 16 grams of the
anhydrous in what ever amount of water is needed. That is
the amount I recommend for one roll of Pan F+ 120. A
faster film will likely require a little more.
Of course it is one-shot.
Dan

Ole · Sep 28, 2004

Ilfofix is a neutral ammonium thiosulfate fixer. Use that, most home mixes are no better. In fact it's better than most, and lots better than "plain hypo".

dancqu · Sep 28, 2004

Ole said:
Ilfofix is a neutral ammonium thiosulfate fixer.

Penta or anhydrous, neither of those two sodium thiosulfates
will spoil. Preservatives and ph modifiers are added to the usuall
off-the-shelf fixers.
If used fresh, the ph neutral, unadulterated sodium
thiosulfates will do all that a fixer can do. No need to add
anything.
To use fresh at processing time just spoon into the needed
amount of water an appropriate amount of the salt. Dan

Ole · Sep 29, 2004

dancqu said:
If used fresh, the ph neutral, unadulterated sodium
thiosulfates will do all that a fixer can do. No need to add
anything.

No, they won't. Sodium thiosulfate is not recommended for some films (and papers), because it won't dissolve silver iodide. Ammonium thiosulfate will, as will sodium thiosulfate with added ammonium.

What makes you think "unadulterated sodium thiosulfate" is neutral?

dancqu · Sep 29, 2004

Ole said:
"Sodium thiosulfate is not recommended for some films
(and papers), because it won't dissolve silver iodide."

That is a complete falsehood. It is in fact the thiosulfate, be it
sodium or ammonium, which complexes well with the halogens of
silver. While the ammonium ion will complex well with the chloride and
some what with the bromide, it has practically no affinity for the iodide.

"What makes you think "unadulterated sodium thiosulfate" is neutral?"

I've measured it a number of times. Most often it's ph measures 6.8.
That puts it very slightly on the acid side of neutral.

If you don't believe me give ammonium chloride alone a try. Dan

Ole · Sep 29, 2004

dancqu said:
Ole said:

... It is in fact the thiosulfate, be it
sodium or ammonium, which complexes well with the halogens of
silver. While the ammonium ion will complex well with the chloride and
some what with the bromide, it has practically no affinity for the iodide.

Click to expand...

Sorry, but...

The point is not the halogens - thiosulfate complexes very well with silver, not halogens. Same for ammonium, another silver complexer - but not as efficient. Ammonium also forms complexes with halogens, but to a much lesser extent. This increases the solubility of the silver halogens, of which sliver iodide is the least soluble. In this way ammonium thiosulfate (or ammonium and thiosulfate) dissolves silver iodide in a fraction of the time it would take without the ammonium. This lets silver iodide be fixed out in a reasonable time, which it won't without ammonium.

I'm afraid you've got the fixing process backwards: The halogen ions are very soluble, the point of fixer is to make the silver unavailable to them by wrapping the silver in tight complexes. And the solubility of the silver halogen compounds play a role in the speed with which this happens - (silver) chloride is more soluble than the bromide which is more soluble than the iodide. About a factor of 10 difference with each step.

dancqu · Sep 29, 2004

Ole said:
- thiosulfate complexes very well with silver -

In reading your post I don't see any disagreement. I should have been
more clear on one matter. Better put I might have said; "Thiosulfate
complexes very well with silver in the presence of chloride ion,
less well in the presence of the bromide ion, and least well
in the presence of the iodide ion.

As you pointed out ammonium does less well in the presence of all three
of the halogens. In fact it's ability to complex silver in the presence
of iodide ion is almost nill. Of course if the amount of silver iodide
is extremly low the entire matter becomes academic.

I've not tested for "Rapid". From reading I've the impression it
applies much more so to papers than silver iodided emulsions.
I'd say as one would expect. Dan

Ole · Sep 30, 2004

What I tried to say is that it's not so much the complexing that's affected by the type of halogen as the solubility of the silver halide. The effect of ammonium can be easily seen with a "clearing test" with a small piece of film. I have done this while mixing my own fixer (see "Chemistry Recipes" section), by putting in small pieces of film before and after adding the ammonium chloride. The acceleration of the fixing action is obvious, and remarkable.

Many emulsions today contain significant amounts of iodide, with the "special grain" films being the prime suspects (T-Max, Delta etc). One paper that contains significant amounts of iodide is Bergger Art Contact, which has a chloroiodide emulsion. "Normal" fixing in a "normal" fixer is not enough for this paper - which I rather like, by the way. After fixing in a "rapid" fixer the image is stable, and will not fog with exposure to light.

mobtown_4x5 · Oct 1, 2004

Is the formulary TF-4 sufficient to clear the high iodide materials?

Ole · Oct 1, 2004

mobtown_4x5 said:
Is the formulary TF-4 sufficient to clear the high iodide materials?

Yes.

It doesn't take much ammonium to accelerate the action to where iodide will be fixed out during normal fixing times (q.v. the recommendation for three times clearing time for many films), and TF-4 contains lots of ammonium. Much more than mine.

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