A question about fixer

Ole said:

One benefit is that the fixer is always fresh, which is great for someone like me who does "batches" every month or so. In the summer I go through a lot of films, but in the winter thing tend to die from old age before I have a film to develop. Winter on the other hand is printing time, so I go through a lot of paper fixer.[...]

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In terms of processing capacity and other factors, I think an alkaline fixer with conventional usage is most economical and least wasteful. I use my house formula, which is buffered at pH 7.5 to 8 range. The benefit of this pH range is that the fixer washes out very fast, and that the fixer has a very long shelf life even after partial use. You can keep a working solution for a year very easily. Another difference with my buffered fixer is that it can be used with acid stop bath with no problem. I can add quite a bit of acetic acid before this fixer becomes acidic enough to affect rapid washing and long keeping properties. The base buffer in the fixer also neutralizes acid in the emulsion layer and paper base quickly, and so the fix washes out fast, whether acid stop or water rinse is used.

While I reuse film and paper fixer, I check the exhaustion level with standard iodide precipitation test. It's pretty safe to use *rapid* fixer until iodide test results in permanent creamy precipitate, as most films fix perfectly well in 4-5 minutes at that point (tested with standard sulfide test). Delta 400 may take an extra minute or two. Also, regular sodium thiosulfate fixer craps out quite a bit earlier than ammonium thiosulfate.

Photo Engineer said:

Ole, a 'cupful' of solid ammonium hypo can be a lot in relative terms depending on how much developer you have. A normal fixer may contain about 120 g/l of ammonium hypo and do a good job fixing. Sometimes less is used.

So, you might want to optimize the amount to save money.

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Oops - I must have misquoted myself!

My "regular" usage is three teaspoons of ammonium thiosulfate in half a cup of water. Less water if I do two 35mm films in a Paterson tank, just to make it fit in there. About 25 g/liter of developer is more than enough.

Ole said:

About 25 g/liter of developer is more than enough.

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Well, that's a good one. Add 25 grams of
anhydrous Ammonium Thiosulfate to each liter
of developer. I sound tame suggesting 20ml of A.
Thio. concentrate per roll to whatever solution
volume of fixer needed. Dan

That's 20ml of 60% solution, or 12g per film. Half a liter developer for a roll of film? it's in the same range - my Paterson tank uses 500ml for a roll (120 or 220) of film. You end up at 24g per liter, I use about 25g...

Ole said:

One of my "perversions" is that sometimes I use no stop at all, nor "fixer".

Instead I dump a cupful of 50% ammonium thiosulfate straight into the developer when I want to stop it.

Within 10 seconds the film has been fixed enough that no further development can possibly take place.

It works; but don't do it just because I said it works!

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The earliest reference to this technique of which I am aware was in the documentation for FR X-22. They mention adding a portion of their Instant Fixol to replace some of the developer to stop development and fix the film.

You guys - I have to laugh! Don't get me wrong, I've learned A LOT from this discussion. But you realize I just had a little bitty question about some TF-4 fixer...

Anyway, keep it up I'll just stand back here and observe!

We're good at that. No question is so "simple and innocuous" that we can't keep it running for at least three pages, developing new sidetracks on the way. It makes for interesting reading and hopeless achives...

Ole said:

That's 20ml of 60% solution, or 12g per film.
Half a liter developer for a roll of film? It's in
the same range .... You end up at 24g per
liter, I use about 25g...

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Yes that's correct, 1/2 liter. One thing: The specific
gravity of that 60% is very nearly 1.3. The weight of
the A. Thio. only is more likely 20ml X 1.3 X 60%. That
be so I'm using 15 + grams. I'd have to think about it
some more to be sure.

Weights-Volumes, grams-milliliters; methods used in
photographic compounding can be confusing. Dan

dancqu said:

Yes that's correct, 1/2 liter. One thing: The specific
gravity of that 60% is very nearly 1.3. The weight of
the A. Thio. only is more likely 20ml X 1.3 X 60%. That
be so I'm using 15 + grams. I'd have to think about it
some more to be sure.

Weights-Volumes, grams-milliliters; methods used in
photographic compounding can be confusing. Dan

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Dan;

That 60% depends on whether it is wt/wt or wt/vol.

I have always taken it as wt/vol, which is what we used at EK, in which case 100 ml of 60% ammonium hypo contains 60 grams of ammonium hypo solid and the remainder (undetermined due to changes in volume of water due to hydrogen bonding and etc) is water to make up the 100 ml.

PE

Photo Engineer said:

Dan; ... I have always taken it as wt/vol,
which is what we used at EK, in which case
100 ml of 60% ammonium hypo contains 60
grams of ammonium hypo solid and the
remainder ... is water to make
up the 100 ml. PE

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Yes, that's correct. My mind must have jumped
track bringing specific gravity into the discussion.
So, Ole's and my amounts are the same; 12 grams
of the solid or 20ml of the 60% concentrate.

I've read of and measured the concentrate's
specific gravity. I needed information to establish
equivalencies twixt the S. and A. Thiosulfates. On
another occasion I used the Sp. G. to determine the
concentration of A. Thio. in some mixed up bottles
of diluted concentrate. Dan