keeping fixer

Bob Carnie said:

Ralph
I am using 1000ml per jobo run of fresh fix, is it possible I would need the second fix?

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No, but why don't you consider rotation processing?

Ian Grant said:

... When Ilford published replenisher research back in the mid 50's about 1 g of silver gets created during development of 12 120 films, roughly the same amount of silver ends up in the fixer. Modern films contain less silver, some like Tmax much less. ...

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It isn't as simple as how much silver the fixer is able to dissolve or hold. During the fixing process, soluble silver thiosulfate and its complexes increasingly contaminate the fixing bath until it no longer dissolves all silver halides.

Think of it this way, if a fixer is exhausted after 24 films, will the last film be fixed just as well as the 1st? Of course not. But shouldn't the last film be fixed just as well as the 1st? Yes, of course. Hence, the two-bath fixing recommendation.

The fresher, second bath ensures that any remaining silver halides and all insoluble silver thiosulfate complexes are rendered soluble, and afterwards all 24 films are fixed the same.

RalphLambrecht said:

It isn't as simple as how much silver the fixer is able to dissolve or hold. During the fixing process, soluble silver thiosulfate and its complexes increasingly contaminate the fixing bath until it no longer dissolves all silver halides.

Think of it this way, if a fixer is exhausted after 24 films, will the last film be fixed just as well as the 1st? Of course not. But shouldn't the last film be fixed just as well as the 1st? Yes, of course. Hence, the two-bath fixing recommendation.

The fresher, second bath ensures that any remaining silver halides and all insoluble silver thiosulfate complexes are rendered soluble, and afterwards all 24 films are fixed the same.

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There's some flaws in that argument because the maximum silver limit where a fixer will still work is around 15 g/litre.


The Mason & Levenson suggestion is that 8-10 gms/litre (their abbreviation) is usual for films.


Ilford currently say:


Silver concentration
The level of silver in a film fixing bath can be allowed to rise to 8–10g/l without serious effect.


And for RC papers:


RC papers can be processed in fixers containing higher levels of silver, 4–6g/l as the paper base is protected on both sides by an impervious polythene coating.


However Ilford recommend 24 35mm films per litre of Hypam at 1+4 which is equivalent to 24 rolls of 120, 96 sheets of 5x4 and 24 sheets of 10x8.


Based on the late 60's figures 12 120 films contain 2 g of silver (as halide), in processing roughly 50% is converted to Silver metal the rest soluble silver complexes in fixer. As there's no cellulose there's no bonding between the complexes and the cellulose which is the issue with FB papers.


Modern films contain less silver so we can expect roughly 1.5 g of silver in the fixer after 24 films, that’s used just 1/10th of the potential maximum 15 g/litre and still less than a 1/5th of the 8 g/litre level, so which ever way you look at it. So that fixer still has plenty of capacity to dissolve far more silver.


Kodak's figures that Haist used were based partly on G.I.P. Levenson and Crabtree's Kodak researchwork up to the late 1950's, using a Sodium Thiosulpate fixer with a hardener, which was then the most typical fixer in use. Later research by G.I.P. Levenson at Kodak (Harrow) and L.F.A. Mason of Ilford into Ammonium Thiosulphate based fixers show quite different results. Crabtree's main research into archival fixing/processing was published in 1943. Ilford don't recommend using a hardener except in exceptional circumstances with Hypam.


G.I.P. Levenson's later research showed that that an ammonium thiosulphate based fixer is much more tolerant of dissolved silver compared to sodium thiosulphate, sodium salts are less soluble than ammonium. Ammonium Thiosulphate clears film approx 4 time faster than a comparable amount of Sodium Thiosulphate and wash times can be reduced as well at the silver thiosulphate complexes are more soluble.


It's worth noting that although rapid fixers have been around for more than 100 years Ammonium Thiosulphate was difficult & costly to produce and until the mid to late 1950's it wasn't economically viable as a commercial fixing agent.


Prior to this rapid fixers used Sodium Thiosulphate and Ammonium Chloride to produce Ammonium Thiosulphate in solution, the downside is there's still a high level of Sodium. Hans Windisch was an advocate of this type of Rapid Fixer and published a formula in 1938 in Die Neu Photo Schule, later Kodal published a similar fixer formula F-7


Take up of rapid Fixers like Hypam (late 1950's) was faster in the UK and Europe mainly because low cost Ammonium Thiosulphate became available in Europe first, it's extremely hygroscopic (adsorbs water) so it's usually shipped in bulk as a solution. Kodak UK sold a similar liquid rapid fixer and Kooadfix AM-33. This was a time when Kodak UK made and sold some chemistry never marketed in the US. Kodinol (their version of Rodinol), HDD (High Definition Developer) and there seem to be others I've never seen in US Kodak books/adverts. 1960 prices show that Hypam was slightly more expensive than using an Ilford Sodium Thiosulphate based fixer.


Kodak switched to Ammonium Thiosulphate in 1966 with the E4 process, the original E3 fixer used Sodium Thiosulphate.


Another fly in the ointment now is Sodium Thiosulphate fixers work poorly with some modern high Iodide films like Tmax and this can lead to problems, Ammonium Thiosulphate is affected far less, although capacity may be reduced as the fixers Iodide level increases.


Current thinking is that very slight traces of Hypo and the unstable complexes actual protects the processed silver in an emulsion, and that over washing etc can itself lead to image deterioration. There's a PDF file of research done more recently by a George Eastman House intern into actual cases of image deterioration. While it's looking primarily at prints some ot the issues are applicable to films.


The problem is that data and research done in the 40's & 50's is no longer valid as the films have changed and there's been a major switch to Rapid fixers.


Ian

Ian Grant said:

There's some flaws in that argument because the maximum silver limit where a fixer will still work is around 15 g/litre. ...

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I'll take the first film fixed in this fixer, you can have the last one fixed in it.

Ian Grant said:

... RC papers can be processed in fixers containing higher levels of silver, 4–6g/l as the paper base is protected on both sides by an impervious polythene coating. ...

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The same is true for films, but that's irrelevant because we are talking about what fresh and contaminated fixer does to the unexposed silver halides. The point was that during the fixing process, soluble silver thiosulfate and its complexes increasingly contaminate the fixing bath until it no longer dissolves all silver halides. Contaminated fixer is not as efficient as fresh fixer. Hence, the one-shot, two-bath fixing recommendation.

Ian Grant said:

... Current thinking is that very slight traces of Hypo and the unstable complexes actual protects the processed silver in an emulsion, and that over washing etc can itself lead to image deterioration. There's a PDF file of research done more recently by a George Eastman House intern into actual cases of image deterioration. While it's looking primarily at prints some ot the issues are applicable to films. ...

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You are ahead of yourself now. This is a washing efficiency issue. We are talking about fixing efficiency and capacity.

Ian Grant said:

... The problem is that data and research done in the 40's & 50's is no longer valid as the films have changed and there's been a major switch to Rapid fixers.

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Yes, but as you already said through your TMax example, not necessarily to the better, as far as fixing is concerned. TMax 'exhausts' fixer sooner than older emulsions. You may not have the safety margin you hoped for when switching to ammonium thiosulfate.


There is little reason to continue this exchange, because one-shot, two-bath fixing is the safest approach anyway. This way all films get the best possible fixing activity, and there is no risk of reaching the fixer capacity limit and underfixing.

By the way, according to my Ilford and Kodak contacts, underfixing (mainly due to contaminated or exhausted fixer) is the number-one reason for image deterioration. It apparently happens far more often than any other processing error.

If one wants to squeeze the last possible fixing capacity out of the fixer, fine with me, but do so at your own risk. If you are interested, I can show you what is left of 15-year-old TMax, fixed in Kodak Rapid Fixer below their recommended capacity limits: They were underfixed and now almost lost.

When you process film or paper, you will not find even close to 100% of the Silver as complexes in the fixer. In fact, only 30 - 70% of the Halides are dissolved and the rest make up the image that you see. This varies depending on subject matter. Film, at a rough estimate, has about 300 mg / ft square of Silver Halide, and papers contain about 100 mg / ft square. For paper, I usually estimate 50 mg of Silver for each 8x10 sheet. This is a rough estimate.

The amount of Silver Halide that can be dissolved in fixer depends on the concentration and the other ingredients as well as the pH. An Ammonium based fixer can hold more Silver complexes than a Sodium based fixer because there are 2 fixing agents in an Ammonium fixer. As concentration decreases (say by using a paper dilution fix on film) the holding ability of the fixer is decreased and some insoluble salts of Silver Halide may be formed and may be retained in the photo product.

Since Silver Halides can form insoluble products with Hypo, it is possible to form them in your film or print and be unable to wash them out. This is why dilution of fixes or over use can be very dangerous to the longevity of your photographs.

PE

RalphLambrecht said:

I'll take the first film fixed in this fixer, you can have the last one fixed in it. . . . . . .

If one wants to squeeze the last possible fixing capacity out of the fixer, fine with me, but do so at your own risk. If you are interested, I can show you what is left of 15-year-old TMax, fixed in Kodak Rapid Fixer below their recommended capacity limits: They were underfixed and now almost lost.

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Well so far in over 45 years of film processing I've never lost or had a single issue with negatives due to fixing. I still make prints off the first Tmax negatives I shot in the mid 1980's just after the films UK release and my 1960's negatives are OK too.

At no point have I suggested exceeding Ilford's practical recommended capacity for films with their rapid fixers, or even getting close to the 8 g/litre figure Ilford mention is possible with no adverse effects.

RalphLambrecht said:

Yes, but as you already said through your TMax example, not necessarily to the better, as far as fixing is concerned. TMax 'exhausts' fixer sooner than older emulsions. You may not have the safety margin you hoped for when switching to ammonium thiosulfate.

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You have no safety margin at all with Tmax films in an older Sodium Thiosulphate fixer in fact it's likely negatives will deteriorate over time as the fixer didn't cope with the Iodide levels, this is why Kodak highly recommend using their Rapid Fixer with Tmax films which uses ammonium thiosulphate. John Sexton found the same and published some extremely good articles on Tmax films, exposing & processing, in the mid 1980's.

Even Kodafix powder which is Sodium Thiosulphate based has been re-compounded in recent years using Ammonium Aluminium Sulphate as the hardener instead of Potassium Aluminium Sulphate as the presence of the Ammonium ions helps with the Iodide levels in Tmax films during fixing keeping complexes soluble. The two mainstream liquid film/paper Kodak fixers are both ammonium thiosulphate based but again now use ammonium sulphite etc instead of the sodium salt

One shot fixing is not always an option, it can be extremely wasteful, I need two litres of fixer to process 12 sheets of 5x4 film in my Jobo tanks. That's a 1/16th of Ilford's recommended capacity of 24 rolls 35mm or 120/96 sheets 5x4 per litre.

My Jobo 2000 tanks pre-date Jobo's rotary processors, but the typical volume of chemistry for rotary use is 250/270ml for a 6 sheets of 5x4 (I do have a Jobo rotary but only bought it 3 days before returning to Turkey) so in terms of fixer usage that's roughly the same final fixer silver content as my last 12 of 48 in 2 litres in reused fresh fixer. That puts one shot fixing into a amore realist pesrpective

So the way I work, roughly based on Ilford's suggested usage is in theoretical terms about a factor of 2 times higher silver content, but then I plate out much of the silver so I get a higher and safer through-put. In practice you may well have a far higher silver content in the spent fixer than I do, so one shot use may not be as beneficial as you think. It's six of one half a dozen of the other. Or as a wise old mechanic once told me if you top a car battery up with tap water it'll last another 12 months, but use distilled water & it'll last a year

We can only really talk about our own experiences, but I have to admit I'm far happy no longer fixing Tmax films, I was always very vigilante keeping an eye on clearing times, I kept 35mm film leaders for testing and always followed John Sextons mid 80's advice of fixing in Rapid fixer until the pink colour disappears.

RalphLambrecht said:

By the way, according to my Ilford and Kodak contacts, underfixing (mainly due to contaminated or exhausted fixer) is the number-one reason for image deterioration. It apparently happens far more often than any other processing error.

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That I don't doubt, I don't think any of the manufacturers data-sheets etc pay enough attention to watching film clearing times particularly with fixer re-use. Even then many don't realise that a film like Fomapan 100 might clear in under 30 seconds, Delta 100/400 a minute and Tmax films have a mind of there own all in the same fixer.

You learn to use a developer & film combination, but many don't realise you also learn how to get the best out of a fixer. I'm not quite sure when I began using Hypam, but certainly over 40 years ago, I used it replenished in 12.5 litre deep tanks commercially 1976/86 there's no issues with any of our negatives - 3 photographers shared the same ID-11/Hypam based deep tank line and it had heavy usage. The line was there before I joined it and later moved continuing into the early 2000's. I did have a brief deviation when May & Baker (now Champion & making all Kodak's chemistry ) wanted me to switch to their chemistry but that chemistry never hit the main film or print darkrooms. Amfix is a superb fixer but it's aggressive, even slight over fixing quickly causes silver bleaching.

Hypam is probably the oldest & best of the commercial Rapid fixers and also one of the highest selling, Ilford Rapid Fixer is essentially the same but doesn't have the buffering needed for adding a hardener.

This aspect needs some thought and probably a separate thread.

People need to be very careful making assumptions that one shot is better, it's a very big compromise with Rotary processing because of the far lower volumes of chemistry used and the higher exhaustion of the chemistry and build up of by-products as a consequence. It's not a better way of working, it can be much less economic, it's just an alternative way of working and what works for one person might be useless to others unless their set up is similar.

Replenishment of developer & fixer can often be the most economic route without any compromise in quality or archival permanence, that’s the older approach and extremely well tested commercially.

As PE hinted in his post the ammonium is the key, and it's needed with fixing some modern films.

Ian

Photo Engineer said:

... Since Silver Halides can form insoluble products with Hypo, it is possible to form them in your film or print and be unable to wash them out. This is why dilution of fixes or over use can be very dangerous to the longevity of your photographs.

PE

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Unfortunately, I have a few negatives (and prints) to prove that statement to be correct.

That's why I discard fixer after each printing session.

It's pretty inexpensive especially when one considers the cost or prints that can get destroyed from bad fixer!

ian the framer said:

I know that I can test fixer with strips to measure the silver content, and therefore tell if it is exhausted, but if kept in a bottle (mixed) does it “go off” and how can you tell? Does the Ph change or is there a visible indication?

Ian

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A measure of the fixer's silver content does not give any clue as to
the fixer's state of exhaustion. The usual test is the film clip test for
film. A similar test can be used for paper fixers. Dan

dancqu said:

A measure of the fixer's silver content does not give any clue as to
the fixer's state of exhaustion. The usual test is the film clip test for
film. A similar test can be used for paper fixers. Dan

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Dan

I think 'not any clue' is too harsh, but 'no conclusive evidence' I can go along with.

dancqu said:

A measure of the fixer's silver content does not give any clue as to
the fixer's state of exhaustion. The usual test is the film clip test for
film. A similar test can be used for paper fixers. Dan

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What is "A similar test"? Still using film?

Ian

ian the framer said:

What is "A similar test"? Still using film? Ian

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Tests using potassium iodide and tests using a film clip
are of the same nature. They both enter into solution
halides of silver which by their presence allow our
determination of the fixer's state of exhaustion.

One method of using a film clip would call for calibration
of the clip against some standard; one such as the iodide
test. Rather than the appearance of a cloudy solution one
would time the clip's exposure then check for
cloudy film. Dan

The Iodide test is very difficult to judge and is therefore inaccurate, often giving you the impression that a fixer is bad when it is not.

PE