Deficiencies in DIY C-41 Chemistry

koraks said:

Just don't forget to do the test with fresh, factory-made C41 developer.

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I think this is part of the problem, that such may not be available (post #19). Except for, I'm thinking, the possibility of Cinestill powdered (?) developer.

Normally my rec would be to simply use a commercial C-41 developer "as is" (mixed according to the instructions). But if one needed to know a pH aim value (and were not using the Kodak-recommended gear) then my recommendation would be to use one's own pH measuring gear on said commercial C-41 developer, then whatever that result is, it becomes the user's standard aim point going forward. So if said user is gonna scratch-mix their own developer then their pH aim is gonna be what they actually measured on a commercial mix. And the main reason I take this position is that I trust the (correct) consistency of said mix more than I trust the capability of some user's specific equipment to get a "correct" pH reading of a color developer.

As a note, user photo engineer, now sadly deceased, once mentioned his use of pH electrodes for such things. (For the newer members he spent a number of years in the Kodak Research Labs, and was a prolific poster here, very generous with his time and experience. ) He said that he/they did not use the Kodak spec pH electrodes, but rather, for difficult samples, used a set of correction factors supplied by the electrode manufacturer.

Ps, a couple of notes... we looked at a number of pH electrodes over the years, mainly in the interest of saving money. The so-called Ross electrode, introduced maybe in the 1980s (?) was one that performed as well, perhaps better, than the Kodak spec electrodes. The downside... I believe they were even more expensive.

A note on troubleshooting electrodes... aside from the problem of pH-sensing glass becoming "fatigued," the other main thing was "clogging" of the junction of the reference electrode. (For users of a single electrode, a so-called combination electrode, both of these functions are built into a single electrode body.) I would refer people to the cleaning instructions in the Kodak H24 motion picture manual that I referred to previously.

If someone wants to scratch-mix these developers without the use of a pH meter I think it might be worth simply making up a set of developers using different amounts of some pH adjuster. Then do some sort of performance based evaluation of the results. Which can be like opening another can of worms.

Thank you Mr. Bill, I have decided that if I truly want to make consistent chemical mix from scratch it is important that I purchase the correct pH meter that is more on spec with the original Kodak specifications. If I can't trust pH readings then there isn't much hope for consistency. I am looking at the Milwaukee MW101 (.02 resolution) meter paired with the MA917B refillable KCL electrolyte probe. I think this combo should deliver the accuracy needed.

In terms of reference solution, I do not have access to a developer that I KNOW will have a specific pH upon mixing. The issue with using the CS developer is my doubt that they deliver a consistent product in powder form. I have gotten varying pH readings between 10.1 and 10.5 upon mixing. This very well could be an issue with my meter, but at least my chemicals give consistent readings day-to-day. 10.5 is very much outside the normal range. I could reach out to CS and ask if they have a target pH for their developer.

That being said, I do have one chemical that I know should read at a certain pH upon mixing. That is my TF-5 fixer which, as has been repeated by the creator Ron himself, should ideally have a pH of 6.5. I have consistently gotten pH readings of 8 (mixed 250ml/750ml for 1L of fixer) ever since I started using it and across multiple batches of concentrate. When I contacted the Formulary they did not have much of an answer. Is there a possibility the meter is ALSO unable to accurately read fixer pH? I had assumed this was more of an issue with the developer specifically, but this calls into question the accuracy of my meter. I have not tried adjusting down the pH of the TF-5.

Mixing more DIY developer today, let's see how it goes.

**EDIT** - Fresh v3 DIY developer tests at pH 10.1 which again should be the EXPECTED reading.

Today I mixed the commercial developer from the ADOX C-TEC C-41 kit. I checked the pH with my pH meter, and it read 10.30. Earlier, I performed a 3-point calibration and checked the meter's pH reading using Milwaukee M10010 pH 10.01 buffer solution. The meter read pH 9.89. So, I assume the correct pH for the new ADOX solution might be around pH 10.15. I conducted the tests at 25°C (77°F).

Spektrum said:

So, I assume the correct pH for the new ADOX solution might be around pH 10.15.

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I'm sorry, but the only conclusion you can draw from this is that your pH meter isn't accurate. That's really all; you can't say anything about the pH of any solution you try to measure in that range.

@koraks, you're right, of course, and I'm sad to see that buying a really expensive pH meter and a suitable, expensive probe (which can die within a year) is a necessity.

I'm starting to doubt whether I should invest so much money in such expensive accessories at this stage (I have limited financial resources right now).
For that price, I can buy a 2x5L set of Fuji Hunt Developer Replenisher 60 Low Volume Air Control + 1L starter + 10L Fuji C-41 fixer and still have money left over to buy 40 rolls of Kodak Gold and not have to worry about pH values at all.
I just have a blast dissolving chemicals and experimenting.
Maybe I should focus on the core of my passion, which is taking pictures on film, and only start worrying about DIY C-41 solutions when these proven commercial kits become unavailable.

@originalwinslow I apologize for going off-topic in your thread. I'll be following your results with great interest.

Spektrum said:

I'm starting to doubt whether I should invest so much money in such expensive accessories at this stage (I have limited financial resources right now).
For that price, I can buy a 2x5L set of Fuji Hunt Developer Replenisher 60 Low Volume Air Control + 1L starter + 10L Fuji C-41 fixer and still have money left over to buy 40 rolls of Kodak Gold and not have to worry about pH values at all.

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You now understand why I'm using Fuji C41 developer. DIY mixing just didn't make any sense.

I went ahead and bought the upgraded meter with a glass KCL probe. We can just ignore my back and forth about whether I might have an accurate meter. I almost certainly certainly do not. I'll hold off on any pH assessments until the new equipment arrives.

Here is the new test from V3 of the HB developer. Results appear almost identical to V2 so I think I have a decent repeatable baseline to work from. The only change I made was to measure the SS via dilution rather than directly on the scale (50g SS in 500ml of water, 2ml of solution =.4g). It would appear that an inaccuracy with SS measurement is not the problem. The pH is next on the list of things to verify. Both HB did not have their pH adjusted after mixing. Still waiting on a new batch of kit chemicals for comparison to a control factory developer.

V3 is on top.

Also included are photos of all the chemicals. I forgot to take a photo of the SS but it looks exactly the same as when it arrived. The KBR is not actually blue, effect of the light hitting the container.

Chems look okay to me. What meter did you order?

ags2mikon said:

What meter did you order?

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Milwaukee MW101 (.02 resolution) meter with manual temp compensation paired with a MA917B refillable KCL electrolyte probe. They wanted to upsell me the MW105 which has automatic temperature compensation but it sounds like it's best practice to test at a standardized temp (20C?). Although I wonder if this caution is now outdated considering advancements in consumer electronics. Jason the salesman at Milwaukee did not have any concrete answers about film chemicals specifically.

Blame this on a lack of knowledge but I am curious as to why it would be best to test at a temperature other than 100F? If the pH fluctuates with temp changes why not test at the point where the chems hit the film? Perhaps it is more about meter accuracy at certain temperatures than pH fluctuation.

I was looking at that one too. I think they also had calibration solution. Please give us a review

originalwinslow said:

V3 is on top.

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Those two strips do look pretty similar to me:


Your CD4 looks OK; that was the one I had some concern about.

originalwinslow said:

50g SS in 500ml of water, 2ml of solution =.4g

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Uh, no. 50g to 500ml makes it a 10% w/v solution, so 2ml = ca. 0.2g of sulfite. I assume it was just a typo and that the math was OK for the amount you really used.
Keep in mind that your sulfite solution may/will not be stable over time. Don't ask me how fast it deteriorates; I really don't know. It depends on storage conditions I guess. Sulfite is an antioxidant, so it'll react with the oxygen in the water, forming sulfate. The result is that the developer will be different in two ways: (1) dye formation is inhibited to a lesser extent, and (2) the pH ends up differently.

originalwinslow said:

If the pH fluctuates with temp changes why not test at the point where the chems hit the film?

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Because the pH of the chemistry is specified at a certain temperature and that's often 25C. See the datasheet/spec sheet for whatever commercial chemistry you use. If you look up the pH, you'll notice that the temperature is indicated along with it.

koraks said:

Uh, no. 50g to 500ml makes it a 10% w/v solution, so 2ml = ca. 0.2g of sulfite. I assume it was just a typo and that the math was OK for the amount you really used.

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Ha! Nope, I definitely did my basic math wrong. An interesting result of my mistake, however, is we are now able to notice that even with half the correct amount of sodium sulfite there is no strong visible difference between the results. I've inadvertently debunked my own theory about what effect small errors in the amount of SS could have, which I'll just count as a net benefit to this process

Well, I'm surprised that halving the amount of sulfite has done so little for dye formation. Indeed, as you say, it demonstrates that a minor weighing error on that ingredient wouldn't have done much. Let's see how it goes with factory-fresh chemistry!

Here is the comparison between v3 and fresh CS developer. HB on the right.

Once the pH meter arrives I will verify if that is the issue. If not, I will try mixing RPC's simplified formula (with the requisite pH adjust) and see how the results compare.

Well, the good news is that your process seems quite consistent! Let's see if the two additional checks yield anything; if not, my proposal would be to start adjusting the formula to bring the result closer to the target.

The question remains as to which negative is the closest to REAL spec. The CS neg has more visible color separation, but is what we are seeing actually excessive cyan dye formation? The HB negative is more yellow, but is that perhaps closer to spec? When considering this I found the following comparison interesting:

Here are the two negatives I posted when comparing my replenishment scheme. One is 500T developed in fresh CS developer, the other with 60+ rolls run through it. Well-exhausted. The film is not Color Plus as in the other test strips, and since it is ECN-2 film cross-processed there are other factors here to consider. But we can still make some general observations.

The exhausted frame is overall much more pink/purple. The fresh CS-developed frame is very uniformly yellow in comparison. While this does not give us a basis for comparison with the other C-41 frames, it demonstrates how color balance in the negative begins to drift with exhaustion. This is the most extreme case, but we can see it is also visible (to a much lower degree) between the fresh CS example strip and one run through developer with 24 rolls already processed. The same shift towards pink is visible, with more cyan in the tree's leaves.

We can begin to conclude that in general, as the developer falls farther off spec, the negative begins to shift more towards pink with more cyan dye (?) visible. If we take this observation to be true in a general sense, that would lead us to believe that in fact the HB developer is closer to spec than the CS developer...

The wrinkle here is that this conclusion goes against our expectations that factory developer would be closer to spec. It is also is not reflected in my conversions. My CS conversion definitely has more saturated colors and lacks the mild yellow tint visible in the HB conversion. So perhaps a correlation here does not mean causation.

Maybe this is all incoherent rambling as I try to make sense of a complicated problem. These results are hard to truly compare without official tests strips and an accurate developer control.

originalwinslow said:

it is ECN-2 film

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So all bets really are off. ECN2 is a really different dye set, the chemistry is different and the hues will be off by a mile when cross-processed in C41.

originalwinslow said:

But we can still make some general observations.

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Maybe you can, but I wouldn't dare venture there...


Top is V3-250D in ECN2, bottom same film in C41.
I do know that if you develop Vision3 in too strong an ECN2 developer (so effectively overdevelop it), its base also trends towards red, which suggests that the magenta/yellow balance shifts towards the former. I've had it happen once by accident.
Your ECN2 negatives processed in fresh developer look really oddly yellow to me; I've not seen ECN2 film do that. IDK what's going on there.

Strange indeed, I'm fairly certain I have never seen Vision 3 negatives that look as magenta as the ones you've just posted. Neither the T or D variants developed in C-41 or ECN-2.

Just for fun here is some 500T developed in fresh Film Photography Project ECN-2 developer. What a difference.

**EDIT actually here is a decent example from a roll of CS 400D (250D equivalent) that I developed the other day in my own DIY ECN-2 developer. It does look similar, but the film base is still not as magenta.

originalwinslow said:

**EDIT actually here is a decent example from a roll of CS 400D (250D equivalent) that I developed the other day in my own DIY ECN-2 developer. It does look similar, but the film base is still not as magenta.

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That looks pretty similar though; I think that's probably just about the same with most of the difference being down to how we photographed the negatives. I showed a quick smartphone snapshot with poor/variable white balance. This is what some of mine look like scanned on an Epson flatbed:

More orange, less magenta; same thing in real life.
Quick linear inversion with neutral S-curve for contrast:


IDK what the composition of the Film Photography developer is and I've never used it. I do know it's based on CD3, but that's about all I know about it. Well, and they use ferricyanide bleach. I use regular C41 bleach on my ECN2 film.

What I do know is that if I correct for the green/magenta balance thing, my ECN2 negatives optically print fine, so apparently they work...

koraks said:

IDK what the composition of the Film Photography developer is and I've never used it. I do know it's based on CD3, but that's about all I know about it.

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FPP only list 2 ingredients, CD-3 and sodium carbonate. Not sure if the chemical lists on these powder developers are complete. The list from the CS ECN-2 developer has almost all the spec kodak ingredients except the bromide and anti-cal.

Funnily enough the CS ECN-2 developer claims to also be a 2-in-1 pre-bath, but I don't understand how that could ever work. First of all the chemical composition of spec pre-bath is very different from the developer, so including borax for example would certainly affect the reaction. Second, If you don't pre-wash the remjet it will all come out in the developer and turn it black as night, so it confuses me how they can claim that a pre-bath is not required/is included in the dev step.

I bought some to compare it with my DIY chems. I have not tested it yet, but certainly will give it a pre-bath regardless.