A Neutral Quick Fixer Formula

bernard_L said:

• Choice of C-41 fix. I found the best price is Champion Mydoneg; a distributor sell it for 30€ plus hipping for 5L concentrate. Is Champion still a reputable brand?
  
  CHAMPION - Fixateur C41-RA Mydoneg Universal pour faire 2x5L à 2x15L - CHIMIE Couleur/Développeuse C41 - PH Distrib.com

  CHAMPION - Fixateur C41-RA Mydoneg Universal pour faire 2x5L à 2x15L de Champion est vendu sur la boutique PH Distrib.com dans la catégorie Développeuse C41

  www.phdistrib.com

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This is the fixer I am using actually in C41 with no problems so far.

Rudeofus said:

In order to get the ingredients dissolved with the least amount of time, I recommend the following procedure:

1. Fill a container with about 60% of intended fixer volume with hot tap water (50-60°C/120-140°F).
2. Add the calculated amount of Sodium Thiosulfate
3. Stir vigorously. The Sodium Thiosulfate will cool down the water substantially while it dissolves. If you do not start with very hot water, the solution will get close to freezing point and dissolution will be extremely slow.
4. After the Sodium Thiosulfate has been dissolved, add the Ammonium Chloride. This will cool down the solution yet more. If the volume is still below the intended final volume, add hot water to reach it. Chances are, that the solution will reach roughly room temperature.
5. Add the Sodium Sulfite and the Sodium Metabisulfate at once and dissolve it. You should now have an ever so slightly milky solution, which should be mostly odorless.

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Maybe this should be added to the resource page?

Kino said:

Maybe this should be added to the resource page?

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Yes, good idea. I've edited it in.

bernard_L said:

Questions to the knowledgeable ones, after doing a little homework.

• pH. Fixers for C-41 are specified having a pH 7.5...7.8, while rapid fixers for B&W are specified pH 5.0...5.5. What are the trade-offs? Acid fixer, that I used so far, allows me (after a brief dip in acid stop) to turn the lights on as soon as the test strip is in the fixer. Neutral fixer will require a longer (30s??) stay in the stop bath. OTOH, neutral fixer is expected to be odorless. Any other trade-offs that i should know of?

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What you think is "fixers for C-41" usually turns out to be "replenisher concentrate for C-41 fixer". Since speed is king in commercial C-41 processing, these machines typically go directly from acidic bleach (well buffered at pH 4.2-5) to fixer, carrying over quite a bit of acidity, therefore the replenisher has to be a bit on the alkaline side to keep the tank at target pH 6.5.

If you mix fixer just from this "fixer replenisher concentrate", your fixer will be at the pH both @koraks and you reported. The fixer itself will work just as well at pH 7.5, but Ammonia smell isn't all that great in open tray processing. There is absolutely no point in buying fixer starter for B&W processing, just add a few dashes of something acidic until the Ammonia smell is gone.

bernard_L said:

• Durability. C-41 fixer is generally sold in a pack of 5L concentrate. I'm a relatively low volume user. How long will the stock fixer keep before it sulfurs out?

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It will not sulfur out. Unlike its acidic peers it will not leak out Sulfur Dioxide, its pH will not go down over time. You can measure its life span in multiple years, and even if you throw half of it away it will be cheaper than typical B&W rapid fixers. If you are a really low volume user, there are are neutral fixers marketed for B&W, and they typically come in 1 liter bottles.


Regarding speed of action: don't get hung up on fixer speed, look for washing speed, that's where you can save time and water. PE was enthusiastic for neutral fixers mostly for their washing speed.

@koraks @halfaman @Rudeofus thank you for your input.
Esp. this :

these machines typically go directly from acidic bleach (well buffered at pH 4.2-5) to fixer, carrying over quite a bit of acidity, therefore the replenisher has to be a bit on the alkaline side to keep the tank at target pH 6.5.
(...)
just add a few dashes of something acidic until the Ammonia smell is gone.

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that explains the reason for the pH value in C-41 fixer

Yes, although I use C41 fixer replenisher without any acid added to it, but my film and paper processing all involve stop bath (or in the case of color negative, acid bleach) steps, so there'll always be a little carryover inherent to the process. Even without it, the fixer will work just fine if you don't acidify it.

A follow-up on my post #19 above. Having 2 and 1/2 bottles (500ml) of Fomafix from a purchase last year, I need to use them before I switch to C-41 fixer. With just pH paper at hand, I used ammonia to neutralize the Fomafix. Starting with 166cc of stock fixer --the amount to make 1 litre at Foma's recommended dilution 1+5-- I added ammonia until the pH paper read "7" (give or take). This happened after i had added 33cc of 22° Baumé (reportedly 11 Mol/litre).

The resulting neutral fixer had no smell --at least far less than the original one. And it cleared a negative clip at least as fast as the non-modified fixer.

So success and thank you to members who provided explanations about the pH of various kinds of fast fixer.

Dear Rudeofus, I have a question about the order of dissolving the ingredients. Your formula does contain sodium sulfite as a preservative and antioxidant, but also as a buffer.

I wonder if it would not be more appropriate to add sodium sulfite as the first ingredient to the solution.

Why?

1. Sodium thiosulfate oxidizes quickly and its fixing power decreases. Water contains large amounts of oxygen and if we dissolve sodium thiosulfate as the first ingredient, the oxygen from the water binds with sodium thiosulfate.

If we add an antioxidant to the water as the first ingredient, then this antioxidant will consume the oxygen from the water, stabilizing the environment and protecting sodium thiosulfate from oxidation.

2. In chemical practice (laboratory and photographic), the rule is often used:

"First the stabilizing component of the environment, then the active reagent"
- to achieve the correct pH,
- to prevent decomposition,
- to avoid undesirable side reactions.

This certainly works in the case of fixers based on sodium thiosulfate with the addition of sodium sulfite as an alkalizing buffer and antioxidant. However, everywhere in recipes I see sodium thiosulfate always as the first on the list, i.e. the first in the order to be dissolved.

3. Sodium thiosulfate, when dissolved in water, cools the solution strongly. Often the temperature of the solution drops dramatically and makes it difficult to dissolve the subsequent components (especially if we dissolve in cold water). Therefore, it is better to dissolve the "smaller" components first, which require less mixing, and then add sodium thiosulfate in batches.

Do I understand correctly? Forgive me, I don't have much experience, but I read a lot and then experiment with chemistry.

Kind regards,
Marcin

Spektrum said:

1. Sodium thiosulfate oxidizes quickly and its fixing power decreases. Water contains large amounts of oxygen and if we dissolve sodium thiosulfate as the first ingredient, the oxygen from the water binds with sodium thiosulfate.

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If we look at this chart here, we can estimate far less than 10 mg/l Oxygen in water. Comparing this to the 200 g/l Sodium Thiosulfate, even when accounting for the far higher molar weight of hype, shows clearly, that this little Oxygen really doesn't matter at all.

Spektrum said:

3. Sodium thiosulfate, when dissolved in water, cools the solution strongly. Often the temperature of the solution drops dramatically and makes it difficult to dissolve the subsequent components (especially if we dissolve in cold water). Therefore, it is better to dissolve the "smaller" components first, which require less mixing, and then add sodium thiosulfate in batches.

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You want to start with the absolutely hottest water you can reasonably start with, which is typically 50°C from a hot water faucet. You do not want it to cool down while you dissolve the Sodium Sulfite. I have never had issues dissolving the other ingredients, but the Sodium Thiosulfate did take its time.

Your input from lab experience is well appreciated here, but in this specific case established practice is, as far as I can tell, the fastest way to get all this stuff dissolved.

Thank you very much for your answer. I am 52 years old. Sometimes I rely on old principles of photographic chemistry from the 80s. I remember that sodium sulfite was always to be dissolved as the first ingredient. The exception were developers containing methol, which was very resistant to dissolving in sulfite.

But by pointing to this chart you cleared up my doubts. Thanks again.

Rudeofus said:

BUT: it is susceptible to mold growth until it has been used to fix. Make sure you use the fixer shortly after mixing it, after that you can store and use it for months.

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Sorry for pump it up but recently, I am using Pyro for development and my rapid fixer is not suitable for fixing that. So I manage to try your formula with really easy to get ingredients and really cheap (everything I get from a farmer supplier shop). By "use the fixer shortly after mixing it", how long can I wait to start 1st development with this fixer? I have just mixed them last night and planned to dev 2 rolls Fomapan in the weekend (which means 3 more days).
Anyway, thank for your recipe.

marhalloweenvt said:

I am using Pyro for development and my rapid fixer is not suitable for fixing that

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If that's because it's an acidic fixer: it's a misunderstanding and an urban myth that this wouldn't be suitable for pyro developed film. It works fine, there's no detrimental effect to the stain.

marhalloweenvt said:

Sorry for pump it up but recently, I am using Pyro for development and my rapid fixer is not suitable for fixing that. So I manage to try your formula with really easy to get ingredients and really cheap (everything I get from a farmer supplier shop). By "use the fixer shortly after mixing it", how long can I wait to start 1st development with this fixer? I have just mixed them last night and planned to dev 2 rolls Fomapan in the weekend (which means 3 more days).
Anyway, thank for your recipe.

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You can use this recipe right after mixing it. The only thing, which could go wrong, is if you mix this fixer and then don't use it, this is when mold growth can happen. Once you have used the fixer, it will last for at least years (or until exhausted).