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Use of highly diluted (34g/L or less) plain fixer with film as one-shot

Alan Townsend

Member
Joined
Dec 7, 2025
Messages
222
Location
Peoria, IL, USA
Format
Multi Format
I have been using this dilution for sodium thiosulphate plain fixer for years with film and find it works great on most regular camera films in 10 minutes. TMAX films take double that. This is mixed up right before use using spoons and discarded after single use. This is a very inexpensive and independent way to fix films reliably. At this dilution, it will continue working for at least two days, unlike strong plain hypo solutions that go dead in a few hours. It clears Xray films like fuji hru quicker and also ortho litho film. Test for clearing time, then double it. Do not use for darkroom prints. Use the cheap clear rice crystal type. Pentahydrate?

I see posting from beginners asking about this, and the recommendation is "go figure it out by yourself with a clip test" or some variation. Here's an answer.

Pros
1. You always have fresh reliable fixer.
2. No more fixer reuse with all that fixer crud going into your film.
3 Wash out quickly due to lower concentration, saving water.
4. Dissolves very quickly at this dilution directly. No need for stock solution then diluting.
7. Ideal for low volume, intermittent home darkroom use.
8. This one gram per fluid ounce. FYI
9. Less need for acid stop since fixer thrown out any way.

Cons
1. Slightly less convnient than fixer reuse.
 
I usually use fixer one shot as well, but I use a rapid C41 fixer instead. However, like you I use it more dilute than how it's normally used, which is aimed at a replenishment situation. Fixing time needs to be extended in some cases, but they're generally shorter than what you observe since this is a rapid fixer. There are many ways to skin this cat!
 
If you look at typical fixer dilution of 1+4 for film, you have somewhere around 150-200 g/l thiosulfate in your soup, and the rated capacity of this is somewhere around 10-12 rolls of film, if that, especially with Sodium Thiosulfate. This means, that your dilute fixer will be close to exhaustion at the end of a single roll, so it will be far away from "a fresh reliable fixer". As silver and halides build up in your fixer, there will be poorly soluble compounds in your emulsion: Silver Thiosulfate (not yet complexed to higher order silver thiosulfate complexes with more thiosulfate), all kinds of mixed salts between silver, halides and thiosulfate. These may remain in your emulsion even after extensive washing, with all the bad effects of these compounds in your emulsion.

So no, it will likely not "wash out quickly" at all, and since the fixer is very slow and alkaline, there is definitely no "less need for an acid stop bath". You may get away with this for some film, and other films like TMX/TMY/Delta3200 may turn brown at some point. I highly recommend, that you check these procedures with a retained silver and a retained thiosulfate test for each film you like to treat this way. The good news is, that you can refix all the emulsions, which fail the test.
 
Yes, that's the whole idea and why we though it out after one use.

Rudeofus said:
so it will be far away from "a fresh reliable fixer".
Click to expand...
Do you understand what a "one shot" means? We mix fresh before use, which is a fresh reliable fixer, then we through it out after one use.

This is exactly one good reason for one shot fixer, so that none of this junk from previous films goes into the fresh and new film being processes.

Rudeofus said:
So no, it will likely not "wash out quickly" at all, and since the fixer is very slow and alkaline,
Click to expand...
The fixer is dead and nearly neutral at the end of one roll, so does wash out quickly.

Your welcome for all the money I'm saving everybody. Now you can blow it all on a new camera.
 
gealto2 said:
Do you understand what a "one shot" means? We mix fresh before use, which is a fresh reliable fixer, then we through it out after one use.
Click to expand...

I take @Rudeofus to be saying this:
Rudeofus said:
This means, that your dilute fixer will be close to exhaustion at the end of a single roll, so it will be far away from "a fresh reliable fixer".
Click to expand...

In other words, it will be fresh fixer that will not be reliable, unless followed up with relatively laborious testing of each roll.
 
I'll chime in here too. Years ago I had an email conversation with Simon Galley, then Ilford Tech Rep, about using very dilute fixer one-shot. He was relaying information to me from the Ilford lab techs, etc.

Two takeaways from that were: Yes, it's possible to use fixer one-shot at higher dilutions, but fixing times have to be extended. Testing for these and for adequate fixation with ST-1 or another residual fixer test was critical to finding the right times.

Second, and perhaps most important to this conversation: there is a minimum dilution needed to ensure that enough ionic density in the solution to initiate and sustain the fixing activity. I was using Ilford Rapid Fixer at the time, but sodium thiosulfate fixers would work similarly. Also, I'm going from dim memory, so my explanation might be not totally scientifically accurate (maybe Rudi or others with more knowledge that I can add corrections/augmentation).

The gist, however is: When dissolved, the ammonium thiosulfate in a rapid fixer disassociates, forming ammonium ions and thiosulfate ions. There are two ammonium ions for every one thiosulfate ion. These act on the silver halides by means of electrical attraction and electron exchange to convert them to soluble compounds. If there are not enough of the ions per unit of solution and therefore enough electrical potential to react with all the silver halide molecules and then the resulting byproducts, and then some to spare for a buffer, fixing will not be complete.

So, even though you've done the math for a weaker dilution using the published capacity for a stronger solution (e.g., a liter a 1+4 will fix 12 films, so 1+9 fixes 6 films, 1+ 19 fixes 3...) you aren't taking the real reactive capacity of any particular dilution into account.

Long story short, the weakest dilution of Ilford Rapid Fixer that could really be safely used one-shot was not much weaker than the 1+9 dilution often used for papers (IIRC, it was 1+12 or something). The weakest I use for film now is 1+9 and then only for small batches.

The whole excursion down the rabbit hole just showed me that, if I wanted adequate fixation, I'd have to use close to the published dilutions and wouldn't be saving that much money at all.

Now I use two-bath fixing for both film and paper.

Best,

Doremus
 
Rudeofus said:
I highly recommend, that you check these procedures with a retained silver and a retained thiosulfate test for each film you like to treat this way.
Click to expand...

This is something I would also recommend for anyone who significantly changes their fixing procedure away from the manufacturer's instructions.

But... if one wants to go down the route being proposed by the OP, another option might be to use this highly dilute fixer in a 2-stage regimen. Essentially, use the first fixer as described. But then follow up with a second equally dilute fresh fixer to "finish off" the fixation stage (presumably dissolving the more complex silver thiosulfate compounds which are otherwise considered difficult to wash out). This second fixer, slightly used, would be saved and reused as the primary fixer for the next roll. However, I would not wanna trust this "plain" fixer, with no sulfite "preservative," in storage... so at least a pinch of sodium sulfite for protection.

FWIW, as some may know, I'm from the background of a substantially large photo lab outfit. One of our chemically related goals was to maintain a substantially high product quality while reducing the chemical costs as far as feasible. There is little doubt in my mind that fine-tuned replenishment systems, using the appropriate processing methods can do this. Especially when combined with "regeneration" of those chemicals where it is possible. Unfortunately most small-scale processors can't pull off this sort of thing; it takes significant support costs in both time and expertise, as well as analytical equipment. And it would be silly to spend, for example, a dollar's worth of effort to save five cents worth of chemicals.

Shifting a bit off topic, it tends to bother me a bit how casual many hobbyists are about discarding their silver (in fixer or blix). Granted there is not much there, etc., etc. And few people know much about dealing with it. But it would be nice, from my viewpoint, if people simply acknowledged that they ARE discarding such silver, and that they HAVE considered alternatives (which are perhaps not feasible for them). Just a bit of a personal pet peeve.
 
Mr Bill said:
And it would be silly to spend, for example, a dollar's worth of effort to save five cents worth of chemicals.
Click to expand...

We can't run down to the local photo store any more, they don't exist. I just checked on Amazon, and the best price I can find for a small volume intermittent home user is $22.00 for a half liter kit of Ilford Rapid Fix. Since it says once you mix a 1:4 working solution for film, you have to toss it after a week. Since I process a roll of 35 mm film about once every other week, this fixer would only last for about five films and 500 ml each at a cost of about $4.40 per roll, almost FIFTY TIMES more expensive than the 8 cents a roll quoted. My fixer costs less than a penny per roll, saving $4.39 per roll, which is an entire roll of film if you bulk load. This is what infrequent users, especially ncluding beginners, face.

What are the inexpensive ways of removing silver from fixer for a home user?
Thanks for the information.
 
gealto2 said:
Since it says once you mix a 1:4 working solution for film, you have to toss it after a week.
Click to expand...

That is not correct.
From the datasheet:


Here is the link for the entire datasheet: https://www.ilfordphoto.com/amfile/file/download/file/1833/product/711/

I use and re-use film strength fixer - typically Ilford Hypam because it keeps so long and is available in large bottles at reasonable cost - and one 5 litre bottle lasts me a very long time.
I mix up two litres (actually US quarts because of the bottle I use) and track clearing time and usage vs. Ilford recommended Capacity information. That bottle lasts me for months.

From the datasheet - the Capacity numbers for Hypam:


Here are the datasheet capacity numbers for Ilford Rapid Fixer:

And for completeness, here are the Replenishment numbers for Ilford Rapid Fixer:
 
MattKing said:
That is not correct.
From the datasheet:
Click to expand...
What I saw on Amazon for that product was 1 week without details. From your data, I was off by a factor of 2, so my fixer only saves half a roll of film. I stand corrected. Your sheet gives a month life in half filled bottles with loose caps, which is the normal way a beginner would store it. For low volume and intermittent, the shelf life is the problem.

{Moderator note - box deleted as per wish of poster}
 
Last edited by a moderator:

No one stores any photo chemical in half filled bottles, there's something that a brief read of any book on darkroom technique would tell you is wrong in seconds.

There is no need to try and reinvent this particular wheel - the process is well understood and documented over many decades.

I use mixed fixer stored in full bottles until it is exhausted, that normally means it lasts much longer than 6 months.

There is absolutely zero point in the exercise you tried in your original post. Zero.
 
  • Alan Townsend
  • Deleted
  • Reason: argumentative and disruptive
gealto2 said:
What I saw on Amazon for that product was 1 week without details.
Click to expand...

Speaking generally, always look for more reliable information than what one might find on a retailer's website - except of course those retailers who link to reliable manufacturer's information.
 
MattKing said:
I take @Rudeofus to be saying this:


In other words, it will be fresh fixer that will not be reliable,
Click to expand...

What I understood from Rudy's post is this: DIY one-shot fixer will be fresh at the start of fixing and loose most of its potency very quickly even before the film is completely fixed. And nearly exhausted fixer trying very hard to complete fixing is not a great idea due to the formation of difficult-to-remove silver-thiosulfate complexes. That's why fixer needs to have higher capacity than what is exactly needed to fix a single roll. And that can be easily ensured by using more Thiosulphate, but won't make the fixer economical for single use.
 
what dilution are we talking about? The subject of discussion seems to be missing in this thread.
 
From a moderator's perspective, I'd like to ask everyone to voice their criticism in a constructive manner. In this case, for instance, it's arguably incorrect that "No one stores any photo chemical in half filled bottles" - evidently, many people do, and it sometimes works and sometimes doesn't (esp. with fixer it's not such a good idea, as many of us know too well). As to the utility of the experiment (cf. "zero point in the exercise"), I think we should in principle encourage experimentation and reporting on such is encouraged, as well as (an especially so) constructive debate on the outcomes and interpretation of such experiments. Thanks for taking this into consideration.
 
Thanks, I do understand what he was saying but don't agree with it. One of the things about a clip test that's never mentioned is that you need to use the same ratio of film area to fixing solution to do that clip test as you use when fixing film. That ensures the validity. The time it takes to clear is doubled to allow for that other stuff to get removed. Most "clip tests" I've read about throw a small clip of film into a large container of fixer. That good, but not as good as a test using the same film area to fixer volume as in the real world. I do my clip tests with the right proportions, so am sure the outcome is correct for me. I've fixing this way for ten years and have no issues with negatives being anything but crystal clear. No turning brown.
 

The only thing, which ensures (or rather say: ensured) the validity of a clip test is the fact, that it was tried with a variety of emulsions and fixers, and that it was observed as a heuristic result. Nobody ever gave a credible explanation for that factor two, it could have been 1.2 or 10.5 for what it's worth. Now if you look at traditional formula collections for fixer, they used a large variety of ingredients, but the thiosulfate amount is pretty reliably between 120 and 300 g/l for film and half that for paper. Since Sodium Thiosulfate Pentahydrate has roughly the same thiosulfate content as Ammonium Thiosulfate 60% solution, this thiosulfate range covers both versions.

What I did not see in all these articles or formula collections was dilute soup, and if you look at the complexing reaction between Silver Iodide and the Thiosulfate anion, you will quickly realize, that the reaction balance at equimolar concentrations does not look favorable at all. You need a robust overhang of Thiosulfate anion to fix iodide rich emulsions. Since such dilute soups were likely never investigated with the depth that went into 200 g/l thiosulfate plus stuff, I would not even take the "fix time is twice clearing time" rule for granted.


If it works for you, then you have heuristically proven this method correct for your setup. The "clip tests" you try to disparage here can justifiably operate that way, since they always assumed an overabundance of thiosulfate ion, which may or may not be the case in your setup.
 

Here is my recommendation, assuming your place of residence is correctly shown in your profile: take a look at Photo Formulary or Freestyle, both have offerings substantially below the price point you listed. If you get a neutral fixer (typically labeled "neutral" or "odorless"), then both concentrate and working solutions will last for well over a year. I still use neutral rapid fixer mixed from concentrate canisters purchased in 2020, and they were sold through a fire sale like offer, which means they have probably spent some time in the store before I bought them. Unlike acidic fixer these will not sulfur out.
 
gealto2 said:
I've fixing this way for ten years and have no issues with negatives being anything but crystal clear.
Click to expand...

Once again, it's fine to state how you do something that you believe works well for you you, but it's irresponsible to try to use that anecdote against the recommendations of manufacturers and contradict what is essentially established knowledge. If @Rudeofus says that your fixer dilution will almost certainly not completely fix your film, his opinion has easily as much weight as yours. You're not offering any proof of anything other than "Looks good to me" so there is no substantial ground for argument.

Personally, I say if you can get what you want soaking your film in sea water, go for it. Has nothing to do with me. And chances are your negatives don't need to last longer than it takes to scan them or make a couple of prints - almost none do. So go ahead with the weak fix method. But don't tell others to do it unless you can objectively prove it does always completely fix the film.
 
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