Is this replenishment scheme going to cause excess development strength?

hwy17 · Jun 20, 2025

The new Kodak 5L kit from Photo Systems does not appear to use a starter solution. The manual calls it a non replenishment kit but Cinestill who is marketing the kit in the USA says you can use it for self replenishment. If the kit is just three part flexicolor developer replenisher then that makes sense, except for the questions raised by the lack of starter.

Cinestill advises a 40ml per roll of 135 replenishment rate.

Here's the replenishment concept:

Mix 1 liter of solution

Take 500ml of solution and process 4 rolls of 135 film in a single rotary batch.

Discard 160ml of used solution.

Return 360ml of used solution to 500ml of fresh solution, leaving an 860ml volume of mixed solution.

Top off 860ml of working solution with 500ml of fresh mixture, creating 1360ml of mixed solution.

Continue this cycle with the main working batch of solution varying in a range of 500ml minimum, 1.5L maximum, discarding 160ml after every 500ml/4x135 processing batch. Main working batch being topped off in 500ml increments.

The math here is hectic and the true replenishment rate would vary inconsistently, but as far as I can tell would always meet or exceed the strength of the prescribed 40ml replenishment rate.

My alternative plan is just to mix 500ml fresh, process 4x135, and discard. Which is more consistent but less efficient. Also if I judge it correctly, an overall stronger solution than the variable strength solution scheme as proposed above.

hwy17 · Jun 20, 2025

As for the lack of developer starter in the kit, the justification that I can imagine must be that the processing volumes are low enough that the developer gets "used" enough in the process.

I.e. If a lab were to mix up 40 liters of developer without a starter and then put a roll of film through that, the developer would be too strong and fresh, but if you use 290ml of fresh developer without a starter on a single roll of 135 film in a single roll Paterson tank, the 1 roll / 290ml ratio is still a high enough "usage" of the chemistry that the developer reaches working strength during the process.

It's also possible that the lack of starter is not truly defensible. Or it's also possible that the kit has been communicated incorrectly, and the three part developer included in the is in fact somehow a developer starter and not a developer replenisher and so is not technically suitable for self replenishment.

I have not reached certainty about this, but Cinestill who markets the kit definetely indicates that it does not include a starter component and can be used for self replenishment.

koraks · Jun 20, 2025

hwy17 said:
Or it's also possible that the kit has been communicated incorrectly, and the three part developer included in the is in fact somehow a developer starter and not a developer replenisher and so is not technically suitable for self replenishment.

This is the case, although to get the terminology correct: the developer is not a 'starter', but just a working strength developer. There's no chemical solution to making a developer that works at the same time as a working strength developer and also as a replenisher. So the self-replenishment story of Cinestill has a hole or two in it somewhere. I expect they assume that people won't notice anyway.

hwy17 said:
Continue this cycle with the main working batch of solution varying in a range of 500ml minimum, 1.5L maximum, discarding 160ml after every 500ml/4x135 processing batch. Main working batch being topped off in 500ml increments.

It's not entirely clear to me how your main volume shrinks back towards 500ml. You described how you go up in 500ml increments, but not back down.
I'm also not sure what the purpose of this system of 500ml increments is. I would just replenish in 160ml increments. You could get 150ml glass bottles (which will usually hold around 160ml if you top them off entirely) and decant your mixed, working strength developer (aka 'replenisher') into those bottles. A properly formulated C41 developer will store for a long time that way (glass bottle, proper & tightly fitting cap, filled to the brim with no air on top), generally well over a year. So just use a 500ml or 1000ml main volume and take out the 40ml per roll that you've 'used up' and replace with fresh developer.

Given the inherent limitations of this chemistry there will be some process drift, but it's entirely likely that this will go unnoticed and will not be experienced as a problem. Is it a 'proper' way of doing C41 in official terms? Nope. But it will probably work plenty good enough for home/amateur use.

Refer also to this thread in which the replenishment situation of current Kodak FlexiColor C-41/C41 is being discussed: https://www.photrio.com/forum/threads/kodak-color-negative-c41-kit.214105/

hwy17 · Jun 20, 2025

koraks said:
There's no chemical solution to making a developer that works at the same time as a working strength developer and also as a replenisher.

This is key to the hole in my own understanding. I have tried to read Flexicolor documentation and failed to firmly grasp it. And in the thread you linked I still feel like I'm ignorant to some basic common assumptions everyone is operating on.

Can you help me shortcut this basic question: What is a flexicolor replenisher strength solution then, is it a solution mixed at a higher strength or is it actually even 40ml of the raw concentrate solutions?

koraks said:
It's not entirely clear to me how your main volume shrinks back towards 500ml. You described how you go up in 500ml increments, but not back down.

The working volume shrinks as 500ml is taken for processing, used, and then 160ml is discarded after use (40ml for each one of 4x 135 rolls processed). So after each batch of processing the volume shrinks by 160ml.

The reason I wanted to replenish in 500ml volumes results from my assumption above that replenishment solution is mixed same as original developer batch strength. I could more confidently mix batches of solution to make 500ml compared to mixing 160ml which would require more precision.

Thank you for your help.

koraks · Jun 20, 2025

hwy17 said:
What is a flexicolor replenisher strength solution then

In the current version of Flexicolor as made by PhotoSys under the Kodak brand, there is no true replenisher. There is only a working-strength developer.

A proper replenisher has two characteristics that set it apart from a working strength developer:
1: It's more concentrated; i.e. the active ingredients (in particular the CD4 developing agent) are present in higher quantities per liter.
2: It lacks or has a lower concentration of halides (typically bromide and a tiny bit of iodide). The idea here is that the halides are added to the developer during development as they dissolve out of the processed film, or they are added in the form of a starter, which is mostly a solution of bromide (potassium or sodium).

hwy17 said:
So after each batch of processing the volume shrinks by 160ml.

And the idea of replenishment is that you replace that with 160ml of replenisher. In the case of present-day Flexicolor developer, you could use the developer for that, which means that activity will trend down for the first few sessions until things stabilize at a certain level that's slightly less active than the initial main volume when it's used for the first time.

As to mixing volumes: in my experience it works well to just mix the entire kit at once and then store it properly as I described earlier. Then use whatever you need as you go along. In addition to glass bottles, some people also have good experiences with so-called 'stop-loss bags' or wine bladders. I myself prefer glass, but that's personal; those wine bladders in principle should work fine too. There's even one person who has frozen his mixed working strength developer and this has been working very well for him.

hwy17 said:
Thank you for your help.

You're welcome!
Try not to overthink things.

How much film do you expect to process on a monthly basis?

hwy17 · Jun 20, 2025

koraks said:
In the current version of Flexicolor as made by PhotoSys under the Kodak brand, there is no true replenisher. There is only a working-strength developer.

Ah! That is slightly reassuring if the situation is indeed just complicated. I could not get the replenishment logic to just click like it seemed like it should. I'll keep rereading the referenced thread to try to expand my understanding.

koraks said:
How much film do you expect to process on a monthly basis?

I've got 20 rolls of 35mm ready to process now and then maybe 8 per month. I would definitely welcome any advice about a processing scheme. Using 500ml of fresh solution at a time to process 4 rolls and then discard is still an acceptable option for me and would also save me some mental effort in it's simplicity. That's what I had settled on until I decided to revisit replenishment. This will be my first time processing film at home.

hwy17 · Jun 20, 2025

I notice now that the Flexicolor document actually references a separate non-replenishment product here on page 5:

https://business.kodakmoments.com/sites/default/files/wysiwyg/pro/chemistry/z131.pdf

KODAK FLEXICOLOR Chemicals for RotaryTube Processors, Small Tanks, and Unreplenished Sink Lines These chemicals are designed for use in unreplenished batch systems—e.g., small tanks, rotary tubes, and small-volume sink lines. They are ready to use as mixed without adding starter. Note: For higher-volume replenished sink-line systems, it is more practical to use larger chemical sizes. You can prepare tank solutions of developer and bleach by adding the appropriate starters to the replenisher solutions. KODAK FLEXICOLOR Developer Use this developer in unreplenished systems. No starter is needed. • Available in a size to make 1 U.S. gallon.

So if I read this and the instruction manual explicitly and ignore Cinestill's interpretation I can reach one simple conclusion: Don't try to self replenish with this kit.

Those with greater understanding here can probably see a lot more nuance but in my beginners position maybe I should stick to my beginner's plan. Use 500ml to process 4 rolls and discard.

koraks · Jun 20, 2025

hwy17 said:
Don't try to self replenish with this kit.

Well, you could and as said it'll sort of work, but it's not a "proper" replenishment system.

hwy17 · Jun 20, 2025

koraks said:
Well, you could and as said it'll sort of work, but it's not a "proper" replenishment system.

To clarify something do you think the replenishment system I've described works (acceptable results, not perfection) with all solutions mixed at the same working strength? Replenishing 40ml of the same strength solution as the original solution. I just wasn't sure if your above correction about replenisher can't be same strength was about precisely correct processes, or something I should change in my modified process.

As you can tell already I go back and forth on this repeatedly. Like now I imagine 500ml sloshing around in a 1L Jobo rotator is gonna face a lot of air oxidation in the process too.

I think that maybe I will start with the one shot process to gain confidence about it then when I finish my first 5L kit and I can decide how I feel about the next kit and whether I'd enjoy being able to stretch it longer.

Thanks again I appreciate it.

koraks · Jun 20, 2025

If you scan your negatives and don't intend to optically print them in the future, then you have a considerable leeway to begin with and you would probably get perfectly fine results that way. If you are planning on optical printing, it can be frustrating if your negatives are kind of variable in terms of density and color balance. Or put differently - it's generally convenient/nice if your film prints in a more or less predictable way. With scanning, color and contrast adjustments are relatively easy to do anyway, so you'll get fine results even from negatives that are perhaps not super consistent etc.

MattKing · Jun 20, 2025

hwy17 said:
I notice now that the Flexicolor document actually references a separate non-replenishment product here on page 5:

https://business.kodakmoments.com/sites/default/files/wysiwyg/pro/chemistry/z131.pdf

KODAK FLEXICOLOR Chemicals for RotaryTube Processors, Small Tanks, and Unreplenished Sink Lines These chemicals are designed for use in unreplenished batch systems—e.g., small tanks, rotary tubes, and small-volume sink lines. They are ready to use as mixed without adding starter. Note: For higher-volume replenished sink-line systems, it is more practical to use larger chemical sizes. You can prepare tank solutions of developer and bleach by adding the appropriate starters to the replenisher solutions. KODAK FLEXICOLOR Developer Use this developer in unreplenished systems. No starter is needed. • Available in a size to make 1 U.S. gallon.

So if I read this and the instruction manual explicitly and ignore Cinestill's interpretation I can reach one simple conclusion: Don't try to self replenish with this kit.

Those with greater understanding here can probably see a lot more nuance but in my beginners position maybe I should stick to my beginner's plan. Use 500ml to process 4 rolls and discard.

It is important to understand that the Z-131 you linked to hasn't been updated since Kodak Alaris was responsible for Kodak photo-chemicals, and that most recent update probably didn't do much to change anything other than add references to Kodak Alaris - which references have recently now been deleted. So the substance is essentially from 2003.
All the chemicals have been revised in terms of source and packaging, even though they have probably been engineered to match their performance in most/many ways.
I'm actually surprised that Kodak Alaris is still hosting a link to it on their web pages, as they no longer have much connection with that part of the industry.
It may be that the developer is packaged as working strength - quite likely - and that the activity drift due to using it as a replenisher as well over the 2.5 or 5 litres in the kits is small enough as to meet the needs of almost all kit users.

hwy17 · Jun 21, 2025

@MattKing Thank you that's helpful context as well.

The more uncertainty there is about this chemistry the more I am inclined to not get creative with it and follow the instruction manual's advice not to self replenish it. I assume those included instructions have at least been approved by Photo Systems for this chemistry.

Being that I'm new to the entire process it's probably best to not get additional variables involved. Processing 4 rolls in 500ml and discarding gives me 40 rolls per kit at a cost around $3/roll and I don't need to save more than that for now.

originalwinslow · Jun 21, 2025

It depends on what your goals for replenishment and chemical usage are.

If you are looking for near-perfect consistency, then this replenishment method should be more than acceptable. If economizing usage of chemicals is most important, then you will end up dumping a lot of good developer that could be reused by simply adjusting development times. This method still gives consistent results even though the developer is slightly exhausted. I have determined that I can comfortably run 30 rolls through a liter of cinestill developer (which I believe is repackaged Unicolor chemicals) by adjusting +1% dev time and have no problems. I know people that stretch it even further. But I am scanning, not optically printing, and as koraks mentioned this gives me leeway if I do get the occasional anomaly. If you are using NLP to convert your negatives then strange color casts are oftentimes just the result of an innacurate conversion anyway.

I recently tried a more rudimentary replenishment "scheme" where I mixed 2L of developer and set aside 500ml. I used the 1.5L for 30 rolls (adjusting dev time) then poured out 500ml and added the 500ml of "fresh" developer. This works out to roughly 1/3 the replenishment strength you originally mentioned of 40ml/roll. I reset develop time to the original 3:30 and got good-density/color in my negatives. Today I developed roll 61 in this same working solution (@5:15 dev time) and the results are still perfectly fine to my eye. I have attached a NLP conversion with no edits.

My goal is minimizing costs as much as possible while still getting consistent results, so for you taking this approach might simply not be worth it if it risks compromising quality.

hwy17 · Jun 21, 2025

@originalwinslow Thank you good to know that the replenishment strength sounds at least strong enough to you. It's doubtful I will be optically printing any time soon, just scanning.

I think I'll see how I feel with the second kit. If I get consistent results through the first kit by using it as a true one shot then I'll be more confident that the rest of my process is consistent enough and ready to try it. I'll also get to find out what actually frequency of processing I get into. It's probably going to turn into a once a month thing.

pentaxuser · Jun 21, 2025

originalwinslow said:
. If economizing usage of chemicals is most important, then you will end up dumping a lot of good developer that could be reused by simply adjusting development times. This method still gives consistent results even though the developer is slightly exhausted. I have determined that I can comfortably run 30 rolls through a liter of cinestill developer (which I believe is repackaged Unicolor chemicals) by adjusting +1% dev time and have no problems.

So do I take it that you add 1% of the standard dev time to each film from film 2 to 30, pouring the developer back into the 1L each time?

As adding 1% of time to each previous dev time results in time in whole seconds and decimal points you use some rounding up or down to whole seconds for the the times? Can you explain what you actually do. Is anything closer to the next whole second rounded up and anything nearer the previous whole second rounded down or is it as simple as rounding up each time as one second is neither here nor there?

Thanks

pentaxuser

brbo · Jun 21, 2025

pentaxuser said:
So do I take it that you add 1% of the standard dev time to each film from film 2 to 30, pouring the developer back into the 1L each time?

As adding 1% of time to each previous dev time results in time in whole seconds and decimal points you use some rounding up or down to whole seconds for the the times? Can you explain what you actually do. Is anything closer to the next whole second rounded up and anything nearer the previous whole second rounded down or is it as simple as rounding up each time as one second is neither here nor there?

Stop trolling.

Guy is operating WAY out of specs and you are concerned about rounding of the seconds? You actually think it matters whether his time at roll xx is 5:15 or 5:16?!

koraks · Jun 21, 2025

originalwinslow said:
f you are looking for near-perfect consistency, then this replenishment method should be more than acceptable

No it will not! It will in fact give fluctuations and be anything except consistent.

30 rolls per liter of C41 is so far out of spec I wouldn't recommend it even if you scan and adjust whatever digitally. It's frankly a waste of perfectly good film.

originalwinslow · Jun 21, 2025

I figured the method I discussed would likely get a strong reaction. It is indeed way outside of recommended specs. The intention is certainly not to mislead anyone into bad dev practice and is only a testament of my personal experience. I'm sure calculated tests would highlight various flaws, but in real-world application I find the results acceptable and comparable to devs in fresh chemicals. Your mileage may vary. Koraks is much more knowledgable than I so I will defer.

This poses a question about developer strength and reuse. I do not particularly take Cinestill's word as law, but their kit's spec is 24 rolls/liter adding 2% dev time. 30 rolls/liter therefore does not stray wildly from their recommendation. Are they committing malpractice with these recommendations? I know some other home kits only recommend 15ish rolls/liter of developer.

pentaxuser · Jun 21, 2025

brbo said:
Stop trolling.

Guy is operating WAY out of specs and you are concerned about rounding of the seconds? You actually think it matters whether his time at roll xx is 5:15 or 5:16?!

I resent that accusation deeply about trolling. I had never seen this kind of process suggested before so was simply curious about it and what it involved. Once I had received a reply then that might have led to a further discussion

I ask a question or questions plural whenever I see something that makes me curious. originalwinslow appears to use 1% extension of time per film rather than say the same time for say 5 films then a jump of 5%

I take statements at face value then ask any questions that arise after I read the statements, such as what was the basis for 1% etc. A dialogue is entered into. It's a great pity that we do not enter information seeking dialogues a bit more

You may know better and differently but I do not, so I ask questions and take into account others' statements. originalwinslow gives an example of what his 1% increase system produced The resultant picture looked fine to me It might have been a 1 in a million piece of good luck and was first time lucky or it might be an example of what his extended development/ replenishment process had produced numerous times I just don't know until I ask

Incidentally I was asking about his first extended and re-use method was about and I am unsure if the example supplied was from that or his second method involving replenishment

I hope this explains why I was not trolling but, tell you what put, me on ignore if it doesn't. Then you have no need to bother accusing me of trolling when I ask other questions on other threads that offend you

pentaxuser

koraks · Jun 21, 2025

originalwinslow said:
I do not particularly take Cinestill's word as law, but their kit's spec is 24 rolls/liter adding 2% dev time. 30 rolls/liter therefore does not stray wildly from their recommendation. Are they committing malpractice with these recommendations?

I think the capacity stated by Cinestill of 24 rolls/liter is already quite optimistic, and that would be my qualification if it were a proper replenishment system. In a system where the same main volume of let's say 1 liter is reused until the 24 roll limit is used involves additional problems of process drift due to halide buildup, pH drift and developer agent oxidation. Extending development time can compensate for the average gamma, but the rate at which color layers develop will differ and tracking will be lost between the layers, furthermore the curve shape will be altered significantly with impact on toe and shoulder regions, so the result will be non-linear crossover and color balance phenomena. I don't doubt that you are so far pleased with the results you obtain. However, I'd like to add a precaution that you might revisit these negatives at a later stage and recognize significant problems that you're overlooking at present. At that point you may decide that your initial optimism has resulted in several films essentially lost to unrecoverable quality issues. You wouldn't be the first to come to that conclusion, and yes, I know how it feels. Not the end of the world, but it has made me realize that whenever someone comes along and says "ooooh you can get 20 rolls out of a liter of C41 no problem, look at these pretty colors, " that the only realistic response is "uh, no, you don't and sooner or later you'll figure out why."

koraks · Jun 21, 2025

brbo said:
Stop trolling.

pentaxuser said:
I resent that accusation deeply about trolling.

Moderator note: please don't accuse people of trolling especially if there's no reason to suspect they are. It's clear that it's not appreciated.

Sirius Glass · Jun 21, 2025

Is this replenishment scheme going to cause excess development strength?

If one is following the manufacturer's replenishment directions, the developer strength should not change from normal.
heh
Just stay away from radical changes in exposure or processing. Remember that the film manufacturer has conducted extensive research and developer of the film, exposure or development - much more than any one of us or a group will every know.

originalwinslow · Jun 21, 2025

pentaxuser said:
I ask a question or questions plural whenever I see something that makes me curious. originalwinslow appears to use 1% extension of time per film rather than say the same time for say 5 films then a jump of 5%

I typically develop 5 rolls at a time and thus jump 5% per development round. Your specific question about percentages of a second could be taken as sarcastic as this variable is relatively insignificant relative to the others stated; such as halide buildup, temperature variance, CD oxidation, pH drift etc. I would agree that it did seem a bit tongue-in-cheek, percentages of a second in this instance are entirely irrelevant. There are so many factors that contribute to the "perfect" dev. In a home setting, with imprecise tools, these quickly become manageable only to a relative degree. My rough calculation is purely based on what I have experienced developing film in my home lab, and I develop 40+ C-41 rolls a month.

The example photo I posted earlier is by no means an outlier, and simply shows an example of what results can look like when using chemicals that may be deemed entirely exhausted by another's standards. I understand that many may fear variance or imperfection in their development practice, but it is also important to keep in mind that we are working in a creative medium for artistic representation. Long gone are the days when film was the only way to produce true-to-life color photographs. I think it is important to see real world applications of how much the chemicals can be stretched to achieve workable results if that happens to fit the desired workflow of another home developer.

koraks said:
At that point you may decide that your initial optimism has resulted in several films essentially lost to unrecoverable quality issues. You wouldn't be the first to come to that conclusion, and yes, I know how it feels. Not the end of the world, but it has made me realize that whenever someone comes along and says "ooooh you can get 20 rolls out of a liter of C41 no problem, look at these pretty colors, " that the only realistic response is "uh, no, you don't and sooner or later you'll figure out why."

I certainly have a history of negatives that I can put into this category. Gradually, I have compared my results to professional labs and tried to tailer my expectations accordingly. Certainly my results do not compaire 1:1 with lab-quality, but the tolerance for variation depends on the photographer. I would argue labs often commit errors in the scanning phase that far outway the errors of a home developer that uses slightly exhausted chemicals but properly converts their negatives. Pleasing results don't necessarily equate with a "correct" processing workflow. This is an infinite debate in the brave new world of film applications in the 2020s.

koraks · Jun 22, 2025

originalwinslow said:
Gradually, I have compared my results to professional labs and tried to tailer my expectations accordingly. Certainly my results do not compaire 1:1 with lab-quality, but the tolerance for variation depends on the photographer.

If with your skillset at this point already see differences between lab-processed film and your own film, then you're waaaay off target. again, if that's Ok for you, I'm not complaining.

originalwinslow said:
I would argue labs often commit errors in the scanning phase that far outway the errors of a home developer that uses slightly exhausted chemicals but properly converts their negatives.

But you can re-scan a negative. Re-processing it ain't gonna happen.

Anyway, I've made my point; carry on, as I implied before, I've been in your shoes and based on that experience I know darn well that the only thing that's going to wake you up will be the massive bruise on your forehead.

brbo · Jun 22, 2025

hwy17 said:
Is this replenishment scheme going to cause excess development strength?

No. It can't. Self-replenishnment from working solution can't ever (even theoretically) cause excess developer strength.

It can't even bring the strength of your replenished working solution to the strength of the original working solution. Unless you are doing 100% replenishment (before somebody asks, yes, 99.95% would be fine as well), of course.

But, you are probably more concerned whether you are replenishing more than you should. The answer again is no. So, what you really are asking is whether you are "replenishing" more than what manufacturer thinks is an acceptable drift from proper developer strength for a home user where they can blame the user and not their false advertising for less than optimal results. To which, obviously, there is not a definitive answer.

Is this replenishment scheme going to cause excess development strength?

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