Guidance on managing basic pH in homebrew chemistry

sfaber17 · Jul 14, 2020

My comment on carbonate with C-41 is based on Stefan's formula or mine. You could look up my old posts which give some of my formula variations and compare to Stefan's. Some other formulas may imply user adjustment.

There are different b&w fixers, some acidic, some basic. I don't know what the extent of the effect is to use the Ilford, but to be safe I use the Kodak color fixer.
It is the least expensive fixer anyway (or used to be). There is an effect though.

As far as doing pH calibrations. The buffers are calibrated for 25 deg usually, so with a cheap meter you should heat it to 25 deg. If the meter is temp compensated, then it will measure and compensate.
Always measure the pH at room temp or 25 deg, not hot or it is hard on the meter and would be way off too.

AgX · Jul 14, 2020

Chromogenic colour films should not be treated with an acid fixer.
But of course this calls for an experiment...

Mr Bill · Jul 14, 2020

GBS said:
Wow, this is the first time I've read definitively: 'don't use B&W rapid fix.' I hate to open a can of worms, but why not? Is it pH alone? My initial research led me to believe the fix pH isn't crucial to the final image.

I dunno about modern films, but historically there have been some cyan dye problems, called leuco cyan dye, where the dye is in an incomplete state. (Leuco is from a Greek word meaning white) If the fixer pH is too low it may be pushed back into this state. I think, from memory, that the Kodak fixer spec is something like pH 6.5 +/- 0.5 (look it up to be sure). Additionally a C-41 fixer generally contains a small amount of free EDTA, which I sorta presume is to deal with any tiny amount of iron carried over (through a wash) from the bleach. But I doubt that it's too important.

If you want to see something interesting, try immersing an RA4 color print that you don't care about into a weak solution of sulfuric acid, say about 2 Normal. (After this you'll understand what a leuco dye is.) It'll return to normal, more or less, with a water rinse.

[Update: re: low fixer pH - see Kodak's Z-131, section 5, page 30 (chart 22) to see the control strip effect (the red plot represents cyan dye, so when the red line goes down, this means there is less cyan dye). Appendix E (page 5-53) has a test procedure for same, using control strips.]

Mr Bill · Jul 14, 2020

sfaber17 said:
As far as doing pH calibrations. The buffers are calibrated for 25 deg usually, so with a cheap meter you should heat it to 25 deg. If the meter is temp compensated, then it will measure and compensate.
Always measure the pH at room temp or 25 deg, not hot or it is hard on the meter and would be way off too.

All the buffers I've ever used (coming in something like 2.5 liter cubitainers) come with a pH vs temperature table. But the real reason one should use 25 deg C is because that is typically where the developer pH spec is given. (Hotter is not gonna hurt the meter, it'll just give the wrong readings.)

GBS · Jul 14, 2020

sfaber17 said:
My comment on carbonate with C-41 is based on Stefan's formula or mine. You could look up my old posts which give some of my formula variations and compare to Stefan's. Some other formulas may imply user adjustment.

This makes sense and gives me a good starting point. Thank you.

sfaber17 said:
I don't know what the extent of the effect is to use the Ilford, but to be safe I use the Kodak color fixer.
It is the least expensive fixer anyway (or used to be). There is an effect though.

Thank you. To start my initial test, I swear I've been reading that Rapid Fix was okay. I was planning to go with Ilford RF since I already have it, but will plan to find the appropriate fix. I'll plan to use color fix moving forward. I'll look for Kodak RA.

sfaber17 said:
As far as doing pH calibrations. The buffers are calibrated for 25 deg usually, so with a cheap meter you should heat it to 25 deg. If the meter is temp compensated, then it will measure and compensate.
Always measure the pH at room temp or 25 deg, not hot or it is hard on the meter and would be way off too.

Great--thank you!

Mr Bill said:
If the fixer pH is too low it may be pushed back into this state. I think, from memory, that the Kodak fixer spec is something like pH 6.5 +/- 0.5 (look it up to be sure). Additionally a C-41 fixer generally contains a small amount of free EDTA, which I sorta presume is to deal with any tiny amount of iron carried over (through a wash) from the bleach. But I doubt that it's too important.

Ahh--thank you. Yes, Rapid Fix is pH 5.0-5.5. Is it out of the question to bring the pH up? As far as the EDTA, I'd be using a stop plus rinse between dev, bleach, and fix.

Mr Bill said:
[Update: re: low fixer pH - see Kodak's Z-131, section 5, page 30 (chart 22) to see the control strip effect (the red plot represents cyan dye, so when the red line goes down, this means there is less cyan dye).

Thank you for going to the effort to share this specific information. I appreciate that a lot. In this reference I am a little lost. P 5-30 is relative to development time. 5-50 contains Chart 22, which references cyan issues with Fixer. I assume I'm meant to study the latter? As far as control strips: I can get a few from my local lab and he'll check them for me, but in general, dialing it in that way is not feasible for me.

One main thing you may be able to help me with: are ECN-2 and C-41 fixer interchangeable? I plan to do both and the only frame of reference for the ECN-2 version I have is the formula.

I'm not quite up to speed on reading the formula well enough to definitively cross reference the C-41 formula(s). If possible, I'd like to use one fix for both, but happy to make my own if that's what it comes down to. Thanks a ton!

Mr Bill · Jul 14, 2020

GBS said:
In this reference I am a little lost. P 5-30 is relative to development time.

My mistake, should be page 5-50, like you already found.

You don't need to do any tests, I'm just making sure you have a literature reference to support what I'm saying. There's so much flaky information on the internet - it's hard to know who to believe. If someone tells me xyz, and then supplies a reputable reference, I feel comfortable locking it into my memory as "known;" otherwise... ?

GBS said:
Ahh--thank you. Yes, Rapid Fix is pH 5.0-5.5. Is it out of the question to bring the pH up?

If I had some rapid fix, and I knew there was no hardener in it, and I had a working pH meter (even a cheap one is fine cuz fixers are no problem to read), and I had something to adjust the pH with, AND I thought it was worth the trouble, then I'd do it. I'd probably look at the MSDS first, in case there was something I'm overlooking.

If the particular fixer is heavily buffered at a lower pH then you might have to "fight" a bit to get the pH up. (A pH buffer is a system of chemicals that makes the pH resistant to change. )

The main thing I'd wonder about is whether it makes sense. I mean, there is presumably a reason why you have the lower pH fix, so if you raise the pH on some, are you gonna have to order in some more low pH fix? Or would it be easier/cheaper to just order in some C-41 fixer?

Mr Bill · Jul 14, 2020

GBS said:
One main thing you may be able to help me with: are ECN-2 and C-41 fixer interchangeable?

The only thing that looks unusual to me is the anti-cal. I doubt it will bother anything. Without that, this is essentially just an ammonium thiosulfate fixer with sulfite ion as the preservative ( the sulfite is coming from both the sodium sulfite and the sodium metabisulfite. Although the latter mainly supplies bisulfite ion it's gonna mostly work the same.).

I'd just double check the pH spec, then try it out. Fwiw the typical reason to combine sulfite and metabisulfite is to control the pH where it comes out. Otherwise you could do something like replace all of the metabisulfite with sulfite, then lower the pH after mixing; the result would be nearly identical.

sfaber17 · Jul 14, 2020

Mr Bill said:
All the buffers I've ever used (coming in something like 2.5 liter cubitainers) come with a pH vs temperature table. But the real reason one should use 25 deg C is because that is typically where the developer pH spec is given. (Hotter is not gonna hurt the meter, it'll just give the wrong readings.)

Yes, thanks, I agree with your comment on the table, but at least with IGFET probe pH meters, I'm pretty sure development temp would be too hot for them from the warnings I remember.

GBS · Jul 14, 2020

Mr Bill said:
The main thing I'd wonder about is whether it makes sense. I mean, there is presumably a reason why you have the lower pH fix, so if you raise the pH on some, are you gonna have to order in some more low pH fix? Or would it be easier/cheaper to just order in some C-41 fixer?

This is an excellent question. In short: I'm beginning with tests for ECN-2 and already have Ilford Rapid Fix--too much, actually. The idea was to share as much as possible, especially to start. (Also, the ECN-2 kit I bought says to use Ilford Rapid Fix--I'm glad I asked. I bought the kit on Etsy and it showed the formula, which matched the Kodak formula, so I went for it, but now it's sold out so I can't find a link to it to share here.)

Mr Bill said:
f I had some rapid fix, and I knew there was no hardener in it, and I had a working pH meter (even a cheap one is fine cuz fixers are no problem to read), and I had something to adjust the pH with, AND I thought it was worth the trouble, then I'd do it.

This is where I'm curios: the Ilford Rapid Fix is non-hardening, so why not try it? Flexicolor fix makes 10L; it's super cheap, but will take me forever to go through that.

Mr Bill said:
The only thing that looks unusual to me is the anti-cal. I doubt it will bother anything. Without that, this is essentially just an ammonium thiosulfate fixer with sulfite ion as the preservative ( the sulfite is coming from both the sodium sulfite and the sodium metabisulfite. Although the latter mainly supplies bisulfite ion it's gonna mostly work the same.).
I'd just double check the pH spec, then try it out. Fwiw the typical reason to combine sulfite and metabisulfite is to control the pH where it comes out. Otherwise you could do something like replace all of the metabisulfite with sulfite, then lower the pH after mixing; the result would be nearly identical.

Thanks, this makes sense, and I appreciate the extra time explaining the 'why' and 'how.' Both C-41 and ECN-2 seem to have pH target of 6.5 so I should be able to share fix between the two processes.

Can you help me with:
1) How long will Flexicolor fix last open and unmixed? If the answer is years, then that is the way to go. Otherwise, I'll end up with waste. I looked through z131 for the answer, but at 99 pages and a confusing TOC, it's hard to for me to find.
2) What can I use to increase the pH in my working solution if I want to test the Ilford Rapid Fix? This is the MSDS which lists Ammonium Thiosulphate in section 8, page 3

Alternatively to either of those, I can order the chems to make my own dedicated fixes -- but Photographer's Formulary has been closed since 7/6. I've emailed about a potential reopen date, but no answer.

Mr Bill · Jul 14, 2020

sfaber17 said:
...but at least with IGFET probe pH meters, I'm pretty sure development temp would be too hot for them from the warnings I remember.

I should be more careful with what I say - my experience is all with conventional glass bulb pH electrodes.

I'm curious about the solid-state electrodes; I recall someone on here referring to them some years ago (maybe it was you?). I'm not finding much on a search for isfet (or is it actually igfet?) aside from "Seabird," which seems to be about ocean monitoring use. Do you have any other references or names to look at? I don't see anything in the Thermo catalog, for example, so...?

* * * * *
[Update: never mind - I accidentally had a search filter set... now I'm finding isfet gear from the usual sources.
First ones I looked at seem to be, uh... extraordinarily rugged, can take higher temperatures than I can, and - what I see so far - something like $400 and up. Plus a special meter is needed.

But otherwise, perhaps the only reason to use a glass bulb sensor now, is to save $$
* * * * *

And regarding temperature, are you saying that the isfet sensor could actually be damaged at C-41 developer temp of ~100 F (~38 C), roughly human body temp? I mean, they would almost have to be shipped in a cold-pack for protection. Or is it only during operation? Just curious if they are viable for general photo use.

Mr Bill · Jul 14, 2020

GBS said:
2) What can I use to increase the pH in my working solution if I want to test the Ilford Rapid Fix? This is the MSDS which lists Ammonium Thiosulphate in section 8, page 3

For some reason my phone browser won't d/l the MSDS, it just queues it up. But you could probably use either ammonium hydroxide or sodium hydroxide. (Use the appropriate protection, per their MSDS - this is no joke - and it's always a good idea to have a way to wash out your eyes in an emergency.) And a whiff of ammonium hydroxide can feel like you got kicked in the nose, so be careful. They have ammonia cartridges for respirators, and I'm not gonna advise YOU, but what I'd probably do is hold my breath for a few seconds, with chemical goggles and gloves for sure, and maybe a face shield. Don't underestimate these things. Just know ahead of time exactly what you're gonna do if you get one of these in your eye, or spill it on the floor, etc. I really don't want to make it sound so bad, but you never know who's gonna read these things in the future, and... well, the world's full of, uh, is it politically correct to say ... idiots?

Ideally you want your pH adjuster in a somewhat diluted solution for use.

As a general rule for checking for compatibility you can check some of the components. If it contains, for example, ammonium thiosulfate (it does) then this tells you that ammonium ion is compatible. Thus you can be pretty sure that ammonium hydroxide is ok for pH adjustment. Now, I'm presuming that it also has sodium sulfite in it, and if so then another sodium ion, such as from sodium hydroxide, should also be ok.

GBS said:
1) How long will Flexicolor fix last open and unmixed?

Sorry, can't say; we never had any sit around. My fuzzy recollection is that typically larger packs of Kodak chemicals would typically list a shelf life of around 1 1/2 to 2 years, unopened.

Fwiw, I've worked with all sorts of regenerated chemicals, mainly bleach and paper blix, even color developers and one brief test with C-41 fix. (Film byproducts in the color film fix make it not suitable for regeneration, even after silver recovery.) The paper blix, however, contains the same fundamental components as a fixer, and it essentially lasts forever in a regeneration loop (which includes silver removal). So the rule I use is, if fixer still has surplus sulfite ion, and the pH is in a sensible range, it doesn't go bad (due to degradation). I've never specifically tried to extend fixer life in a bottle, but I'd probably bet a lot of money that it will. What I'm sorta hinting at here, is that if you have mixed fixer starting to go bad, you can more than likely rescue it by adding some sulfite.

RPC · Jul 14, 2020

GBS said:
Can you help me with:
1) How long will Flexicolor fix last open and unmixed? If the answer is years, then that is the way to go. Otherwise, I'll end up with waste.

I have stored Kodak C-41 Fixer concentrate in full, tightly sealed, glass jars (I use canning jars) for more than five years with no sign of degradation.

GBS · Jul 15, 2020

Mr Bill said:
(Use the appropriate protection, per their MSDS - this is no joke - and it's always a good idea to have a way to wash out your eyes in an emergency.) And a whiff of ammonium hydroxide can feel like you got kicked in the nose, so be careful. They have ammonia cartridges for respirators, and I'm not gonna advise YOU, but what I'd probably do is hold my breath for a few seconds, with chemical goggles and gloves for sure, and maybe a face shield. Don't underestimate these things. Just know ahead of time exactly what you're gonna do if you get one of these in your eye, or spill it on the floor, etc. I really don't want to make it sound so bad, but you never know who's gonna read these things in the future, and... well, the world's full of, uh, is it politically correct to say ... idiots?

I can't tell you how much I respect and appreciate this. Thank you. I have an exhaust fan and a mop sink I can get my eyes under; I hope it doesn't come to that and my goggles and caution are enough. I just ordered a pair of 3M 6004 for my respirator, too. I likely won't end up tinkering with B&W fixer -- putting a round peg in a square hole so to speak. But I feel good knowing where to start.

Mr Bill said:
Thus you can be pretty sure that ammonium hydroxide is ok for pH adjustment. Now, I'm presuming that it also has sodium sulfite in it, and if so then another sodium ion, such as from sodium hydroxide, should also be ok.

I'm doing my best to follow you! I aced Chemistry 101 but we were allowed to use our notes on exams and I just relied on those.

Mr Bill said:
So the rule I use is, if fixer still has surplus sulfite ion, and the pH is in a sensible range, it doesn't go bad (due to degradation). I've never specifically tried to extend fixer life in a bottle, but I'd probably bet a lot of money that it will. What I'm sorta hinting at here, is that if you have mixed fixer starting to go bad, you can more than likely rescue it by adding some sulfite.

Thanks for the tips. I have B&W fixer well-stored that's way past it's printed life but passes the film clip test. I realize the "life" isn't something I'll get a specific answer to. What I'm trying to do is decide if I'll be able to get through 10L of the Flexicolor before it goes bad. But I think I figured it out.

RPC said:
I have stored Kodak C-41 Fixer concentrate in full, tightly sealed, glass jars (I use canning jars) for more than five years with no sign of degradation.

Thank you! I assumed this is the case. Like I said above, I assume it'll last a while. Breaking it into separate jars was something else that came to mind. I appreciate you offering a vote for that if I do go the Flexicolor route.

Thanks a TON for the feedback. Since I'm mostly testing ECN-2 first, then adding in C-41, I'm either going to mix the ECN-2 fixer from scratch, or bite the bullet on the bulk. I'll likely stay away from re-engineering B&W fix. For now.

Anon Ymous · Jul 15, 2020

@GBS Typically, BW fixers are acidic, although there are few exceptions. Their acidic nature makes them susceptible to sulfurisation, ammonium thiosulfate breaks down and releases elemental sulfur. Once this happens, it's better to throw this fixer away. I've seen this happening with Ilford fixers, even unopened bottles that have been stored long enough may sulfurise. C41 fixers on the other hand are nearly neutral and have far better shelf life, that's why RPC's fixer has lasted that long. If you can source C41 fixer for a reasonable price, go ahead and buy it. If not, you may try sourcing ammonium thiosulfate solution. This is also used as a fertiliser (nowadays perhaps the top application), so shops with farming supplies are a possible source. IIRC, others have reported that some of these fertilisers aren't very pure, making their application in photography debatable, but I've been lucky, mine was clean and clear and has kept very well.

GBS · Jul 15, 2020

@Anon Ymous Thank you for the thoughtful and thorough breakdown. I appreciate knowing why my B&W fixer has a shorter lifespan. I discovered the fertilizer connection yesterday. I'm nearing some ECN-2 tests and can get a liter of working Flexicolor fix from my local lab for the initial tests. If they turn out half-worth trying again, I'll probably mix the ECN-2 formula and share it with any C-41 I do (which is secondary at the moment). B&H sells ammonium thiosulfate (the Formulary does, too, but they have been closed since 7/6 for maintenance).

If the Flexicolor has a potential lifespan of years, concentrated and stored well, then I'm much more comfortable getting the 10L mix. I'm splitting it with a friend, so that's not unreasonable at all if it lasts. Two great options. Thanks!!

Guidance on managing basic pH in homebrew chemistry

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