4 years old fixer concentrate still working, what to expect?

Ok so this is mad, and I know I shouldn't have been doing this but here goes. I bought my bottle of fixer concentrate in January 2022 when I first started developing BW film (Adox Adofix plus), knowing it could last me around 1 year max. I have been keeping it in the dark and in a somewhat controlled temperature environment. The thing is, even after a year the working solution was still going strong: film goes completely clear in around 20 seconds out of 4 minutes of expected fixing time. I'm not a frequent shooter, so I never completely "discharged" a working solution, but I thought it would go bad after a few months and be forced to mix again.
Well, it's been 4 years now and I have only ever mixed the working solution three times. Never did it run bad, it still kept clearing the film in 20 seconds, but I felt bad keeping it for more than a year. I mix the working solution with distilled water and keep it air tight. I test the working solution every time I develop.
The 4 years old concentrate is not air tight, and it shows no precipitation whatsoever, it's still clear as day.

I know the fixer does not only clear the film but it also preserves it, so what should I expect? Will my negatives tragically disappear eventually? I probably should have tossed it way before, but I just didn't have the heart as it is serving me so well!

My experience with Adofix is the same. After 6-7 years the concentrate does not show any trace of oxidation or sulphur precipitation. Really remarkable...

lorenzoalinari said:

it shows no precipitation whatsoever, it's still clear as day.

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Then the fixer is just fine.
Sometimes it lasts for years. Sometimes it goes bad within a year. You never know what to expect. But as long as a fixer concentrate is clear as water and there's no precipitation on the walls of the bottle, it's just fine and as good as fresh fixer.

Totally normal in my experience. I'm working out of a bottle of Kodak flexicolor fixer concentrate that's from 2019 and it's still perfectly fine. I mix up a fresh liter of working solution every few months

That is really good to hear! I guess I don't really have to toss the working solution if it's still clearing the film then?

lorenzoalinari said:

That is really good to hear! I guess I don't really have to toss the working solution if it's still clearing the film then?

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I wouldn't. Long as it's still clearing in reasonable time, it's still doing its job.

thinkbrown said:

I'm working out of a bottle of Kodak flexicolor fixer concentrate

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This is near-pH neutral and as such inherently more stable than the decidedly acidic fixers.

koraks said:

This is near-pH neutral and as such inherently more stable than the decidedly acidic fixers.

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Oh interesting, didn't realize that made a substantial difference in lifespan.

Yeah, if you take a 60% solution of ammonium thiosulfate (which is close to what a color fixer concentrate really is, give or take a few additions) you'll find it's perfectly stable for pretty much eternity. Lowering the pH makes the thiosulfate deteriorate and break down into sulfur. You can actually accelerate this, too, by adding a strong acid to a thiosulfate solution.

koraks said:

Yeah, if you take a 60% solution of ammonium thiosulfate (which is close to what a color fixer concentrate really is, give or take a few additions) you'll find it's perfectly stable for pretty much eternity. Lowering the pH makes the thiosulfate deteriorate and break down into sulfur. You can actually accelerate this, too, by adding a strong acid to a thiosulfate solution.

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Good to know - what about alkaline fixers?

Should be stable as well, but I have no experience with them since I personally don't really see the point of alkaline fixers (yes, I know about supposedly faster washing of FB).

loccdor said:

Good to know - what about alkaline fixers?

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All other things being equal an alkaline fixer will have as long a shelf life as a neutral fixer.

loccdor said:

Good to know - what about alkaline fixers?

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Moersch states that their ATS alkaline fixer concentrate can last from 5 to 8 years once opened
I really wonder why that isn't more popular, are there any downsides compared to acidic fixers?

I don’t know about Adox, but I had bought 2-3 bottles of ilford Rapid Fixer concentrate - after 7-8 months something happened to it. At first glance the concentrate looks fine, but on closer inspection you can see white elongated crystals on the surface. After dilution it works, but it turns completely black after just 2-3 days.

lorenzoalinari said:

Moersch states that their ATS alkaline fixer concentrate can last from 5 to 8 years once opened
I really wonder why that isn't more popular, are there any downsides compared to acidic fixers?

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A potential risk with an alkaline fixer is development restarting in the fixer if there is developer left in the paper/emulsion and/or carried over into the fixing bath. Another minor thing is odor (if that is of concern). Further below neutral and you get more of the typical acrid smell, further above neutral and you get more ammonia smell.

Neutral / near-neutral slightly acidic is the best of all worlds.

Historically fixers were acidic because hardening fixers were common and the usual alum hardeners required an acidic pH.

I mix my own TF-2 fixer and never have a shelf life problem with it. The Adox Adofix sounds like another really good Adox product. I use there XT-3 film developer and love it. +1 to Adox!

lorenzoalinari said:

I really wonder why that isn't more popular, are there any downsides compared to acidic fixers?

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I think there's your answer. And of course, Adofix in 1000ml bottles isn't necessarily the bottom end of the market, either.

The thing is, there's just very little advantage to an alkaline fixer.The "For Staining Developers" is arguably misleading since staining developers really do not need an alkaline fixer. It's a myth that just won't go away.

Acidic fixers are an ancient invention, and they still have their place. They work better in a sloppy darkroom environment where there is significant developer carryover into the fixer.

An acidic stop bath between the developer and an alkaline fixer is a must.

My fixer of choice is Moersch ATS alkaline fixer, as it is fast and significantly reduces washing time when working with FB papers.

For film and RC papers any acidic fixer is perfectly fine, the cheaper, the better.

Milpool said:

Another minor thing is odor (if that is of concern). Further below neutral and you get more of the typical acrid smell, further above neutral and you get more ammonia smell.

Neutral / near-neutral slightly acidic is the best of all worlds.

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Sounds a bit like the porridge when Goldilocks had breakfast with Andrew O'Neill's Coquitlam bears

pentaxuser

I'll have to take your word for it. Within Canada I've never been west of Toronto.

pentaxuser said:

Sounds a bit like the porridge when Goldilocks had breakfast with Andrew O'Neill's Coquitlam bears

pentaxuser

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