C-41 replenishing rates vs working tank volume

So I'm planning to start manual processing films myself using Fujifilm C-41RA chemistry (intended for minilabs).

I have read every technical paper I could find and I'm now aware that the replenishing rates of the chemistry are also dependent on the working tanks volumes, but there was nowhere I could find a guideline for a proportion of replenishing volume vs tank volume. There is just no mention on Fujifilm nor on Kodak C-41 chemicals technical sheets other than recognizing it as a factor, but no numbers or whatsoever. I guess that a minilab tank size is expected, but they do come in different sizes (5-10L i think). Overreplenishing is mentioned as a problem. This is my main concern as my working tank will likely be small (1L) so as not too waste much when re-mixing new tanks (a tradeoff for consistency). If I were to replenish say 50ml for each roll as suggested by the technical sheet, I'm sure I'll have an overreplenished tank pretty soon. On the other hand, underreplenishment is obviously a problem, too. The developer is the only solution to be concerned. The one that's available where I live is one you get by mixing a starter with a replenisher that comes as a single solution, and water.

It seems that Fujifilm hasn't published a detailed guide as Kodak's old "131" pdf. There are a few guides they published, all of which I found incomplete, outdated, not meant for the exact same chemistry they sell today.

Before getting dissuasive advice I just want to say the following: I'm aware there are so many things to consider, so much to put together from the notes I've been taking during the past weeks before I proceed to buy the stuff. Perpetuating a working tank solution is not the plan, but a repetitive replenishing cycle for some time before mixing a new working tank is needed to make this economically feasible where I live (prices are 4x the US prices for this chemistry). I know there is no definitive guideline, and that exhaustive testing of solutions with test strips has to be done periodically to get consistent, high quality results. (Minilab tanks will deviate from acceptable concentrations even when following the datasheets by the letter and having a high throughput. If complete testing can't be run the best thing to do is to discard and mix new working tanks from time to time). I just need a good guess to start with, an educated guess for this 'replenishing rate:tank volume' ratio. I won't be using test strips and a densitometer, at most I will do pH and SpG metering. I don't expect optimal processing, though I want it to be quite good. To have my films processed by local labs is not only expensive, but unacceptable to my quality standards. There's really no other option than doing it myself. Rigorous storage of chemicals will be carried out. It is likely that the chemicals will be split between some friends and I so as not to waste much due to expiration and oxidation, and it's also likely for me to start offering film processing services where I live.

I'll be happy to share my procedure in detail if I get to make it work. Any help will be appreciated!

The RA C41 chemistry mainly involves different bleach, (also fixer). I replenish the bleach, it's expensive. For Developer I've always used Kodak Flexicolor chemistry, it's cheap, I use 1 shot. Fixer can be replenished pretty easily.

Smallest replacement volume "tank" I've used is 2L IIRC. Trying to replenish C-41 developer without control strips is tricky.

Welcome aboard @rucho!
I think you've got all the bases covered and I'm afraid I can't give any more specific guidance than what you've already determined yourself. I don't think anyone on this planet can give you a better ballpark guess than what you'll find in the Tech Pub for your particular Fuji chemistry w.r.t. replenishment rates. The reason is mostly because the chemistry isn't intended to be used in the way you intend to use it. Which in itself I wouldn't lose any sleep over, but it does mean that when it comes to proposing a replenishment rate for your developer in your particular situation, all bets are really off. It depends a lot on how you store that one liter (for instance) of working stock, how much it oxidizes to the air while being used and thus how often it's used in the first place, etc.

You state that the official replenishment rate would quickly result in over-replenishment; I don't think that's necessarily the case. Bear in mind that the developer shifts in activity due to a couple of factors:
* Oxidation of the developer to air. This is curbed in C41 developer by the addition of hydroxylamine sulfate, which scavenges the oxygen before it can get to the CD4 developing agent. Of course, this only slows down the rate of oxidation, and also only temporarily - it doesn't entirely stop it.
* Leaching of halides from the developed film into the developer. The halides act as a restrainer and will also affect the development ratios between the different layers, and they affect inter-layer image effects (which is why a trace amount of iodide is in there to begin with).
* pH shift due to interactions between the developer and e.g. the gelatin emulsion, but also uptake of CO2 from the air etc. This effect isn't necessarily very strong, but if you re-use a small working volume over a long period of time, it'll become a factor at some point.
As you can see, part of these factors are related to time, storage conditions etc. Others are related to the actual film surface (and even type of film) processed. I would expect that the latter group of factors is dominant provided that you store your working strength developer reasonably well, prevent contamination with other chemistry etc. This would mean that replenishment primarily serves to restore the loss/change of development activity due to actual film surface processed. The implication is that overreplenishment is less of a risk due to working with a small tank volume.

The TL;DR is that I'd start with the manufacturer's recommended replenishment rate, regardless of the small working stock volume you intend to use. How stable the replenished developer will be - there's just no telling, and the only way to really keep track of this would be to do periodic testing with actually developed film. You've apparently eliminated this possibility, which puts you at the mercy of the gods. There's not much I could recommend except to urge you to reconsider this choice, and perhaps make some test strips yourself that you can periodically use, and that you could perhaps analyze using a scanner or simply your enlarger and some color paper. It'll never be as good as actual densitometry, but it may still allow you to spot gross deviations from spec - which, apparently (and sensibly IMO) would be good enough for your purpose anyway.

Note that tracking SG and pH will give some vague idea of developer condition, but e.g. halide content of the developer can build up virtually entirely undetected to a point where the developer is giving really wonky results and both SG and pH may still read perfectly fine. So they're only a fairly poor proxy and really not a reasonable substitute for assessing actual developer activity/performance.

rucho said:

it's also likely for me to start offering film processing services where I live.

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Anyone should do as they see fit, but I'd urge you to consider putting a better QA process in place than you've outlined in your post if you're going to do this commercially. It's one thing to do a seat-of-the-pants approach for your own work; when offering it to paying customers, it becomes a different reality in my view. But this is perhaps more about business ethics than about the technical side of photography.

PS:

rucho said:

It seems that Fujifilm hasn't published a detailed guide as Kodak's old "131" pdf

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Not published publicly, but they sure have the same kind of information. The usual way of working with Fuji is that you contact them with your questions and they help out. The help they extend comes in the form of direct answers to your questions and/or custom publications of Tech Pub documents that are then issued to you to address your specific questions. For C41 lab chemistry, I suspect you may be working with the products made by Fuji Hunt in Sint Niklaas, Belgium. Contact info is here: https://www.fujifilm.com/ffbe/en/about/office The office you want to contact is the one located at 'Europark Noord 21-22'. They have a technical support department; ask to be put in contact with them. Note that this ONLY applies to Fuji Hunt chemistry.

rucho said:

I have read every technical paper I could find and I'm now aware that the replenishing rates of the chemistry are also dependent on the working tanks volumes, but there was nowhere I could find a guideline for a proportion of replenishing volume vs tank volume.

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Hi, strictly speaking replenishment rates DO NOT depend on tank volume.

However, the manufacturers typically DO recommend a minimum tank turnover per some time period. So it sorta looks like the replenishment rate should be somehow related to tank volume.

Best interpretation of this... in a processing machine a certain amount of the developer is exposed to air; consequently there is some evaporation as well as oxidation of certain chemical components. So there is gonna be a certain imbalance in the chemical components, and it can vary depending on the situation. Presumably this is gonna be kept within reasonable limits by specifying a minimum tank turnover. But you cannot just increase the replenishment RATE, related to film quantity, because a different sort of chemical imbalance will occur.

So there's no simple answer to your dilemma. The best thing I could suggest is to drastically limit the exposure of your developer to air, both during processing AND storage, and to find some way of "monitoring" the developer activity. (Process Control Strips are most definitely the "correct" way to monitor developer activity.)

What sort of processing machine/method are you planning to use?

rucho said:

I won't be using test strips and a densitometer, at most I will do pH and SpG metering.

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Neither of these will be that helpful anyway (at least for developer). Fwiw color developers are difficult to get good pH numbers on; you're not likely to get good results without a fairly expensive pH electrode, especially with a seasoned developer. And the sp gr won't be much use in identifying developer oxidization, which is a big deal.

Ps, I largely concur with koraks. I would point out, however, that the developer replenisher needed, although normally specified per area of film, actually depends more on the actual amount of silver developed. For example, unexposed film will barely affect the developer, whereas heavily exposed film might need more than double the spec replenishment rate. But there is no simple way to determine the amount of silver developed, so we tend to rely on the quantity of film. This is a major reason why commercial photo labs need to monitor with control strips.

I have the Fujifilm doc TB816514 which relates to their c41 developer. it shows the replenishment rate of 40ml per 35mm roll and 52-68ml per 120 roll. I use 25ml per 4x5 sheet, a guess, and the results are good. I have used these amounts with my 1 liter paterson tank for years and get great results

john

destroya said:

I have used these amounts with my 1 liter paterson tank for years and get great results

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Hi, given that the OP seems about to begin processing C-41 for the first time would you mind telling what you mean by "great results?" Do you verify in-spec results via control strips? Or verify that bleaching is complete? Or do you mainly mean that you have never noticed a problem, etc.?

destroya said:

their c41

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Please note that Fuji have several C41 developers in active production and several more that have been produced in the past. They differ w.r.t. replenishment rates, in particular. One cannot (should not) assume the same replenishment rate across different products. Replenishment rates for Fuji C41 developer range from 21ml/(135-24) to 60ml/(135-24). That's a factor 3 difference between the extremes.

As far as I understand, the minimum tank size that is given is 5 liters. Also, the amount of replenisher depends on both the area and the film material itself.
It seems that replenishment the developer at home is not appropriate.

Thanks to everyone for all this information. I will reconsider the use of test strips. Unfortunately, I don't think they are available where I live.

koraks said:

Not published publicly, but they sure have the same kind of information. The usual way of working with Fuji is that you contact them with your questions and they help out. The help they extend comes in the form of direct answers to your questions and/or custom publications of Tech Pub documents that are then issued to you to address your specific questions. For C41 lab chemistry, I suspect you may be working with the products made by Fuji Hunt in Sint Niklaas, Belgium. Contact info is here: https://www.fujifilm.com/ffbe/en/about/office The office you want to contact is the one located at 'Europark Noord 21-22'. They have a technical support department; ask to be put in contact with them. Note that this ONLY applies to Fuji Hunt chemistry.

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Thanks for this info, too.

rucho said:

I won't be using test strips and a densitometer, at most I will do pH and SpG metering.

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rucho said:

To have my films processed by local labs is not only expensive, but unacceptable to my quality standards.

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I find these two comments to be contradictory. (no offense intended). Is the lab also "flying by the seat of their pants" and not using control strips?

Just out of interest, how many films will you be processing on average in a 30 day period?

What size developer tank do you intend to use?

From my own experience and in my opinion, if you want to use a replenished system then you should use control strips as part of your monitoring and quality control. Otherwise the process can go quickly out of control. When you can see it in a developed film then it's too far gone out of control.

BTW the developer tank volume for a lab, just a rule of thumb, was to use at least the developer tank size (say 10L) of replenisher in a month. If it was less than this then not enough film was being processed and the developer replenisher rate might need to be increased or a low volume replenisher used.

If you are really ambitious you could make your own strips, at least be able to check density.

Personally I think with small tanks you're better off one shot on the developer.

Bleach replenishment rates are really small.

Hopefully you can find the starters.

I have discussed this topic with koraks and both we have arrived at the same conclusion. For rotative in a kind of jobo machine is better to use one-shot developer (maybe with inversion technique is possible replenishment´). About the ml Fuji recommends 60ml per 36exp roll. I would be more conservative and use 70ml. But this is the reason I have ended with one shoot. I prefer not to use used chemical to save 150ml of chemicals when I use jobo reels tank.

Next month I’m going to make some strip measurements and I will post results.

I use environeg r60 from Fuji.

I use replenishment on bleach 50ml each batch of 5 reels.
and 50ml of fix every batch.

But I told you next month all my results

I replenish my liter kit but I am only using 500ml at a time. No problems have arisen over 20 years.

Sirius Glass said:

I replenish my liter kit but I am only using 500ml at a time. No problems have arisen over 20 years.

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Is this for C41 and colour film????

Sirius Glass said:

I replenish my liter kit but I am only using 500ml at a time. No problems have arisen over 20 years.

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I suppose you do with Jobo multi tank and 5 reels per batch.
could you tell us your replenishment rates? And how many rolls you develop per week?

Are you using champion, Kodak, ….? Standard kit or minilab kit?

thank you

rucho said:

So I'm planning to start manual processing films myself using Fujifilm C-41RA chemistry (intended for minilabs).

I have read every technical paper I could find and I'm now aware that the replenishing rates of the chemistry are also dependent on the working tanks volumes, but there was nowhere I could find a guideline for a proportion of replenishing volume vs tank volume. There is just no mention on Fujifilm nor on Kodak C-41 chemicals technical sheets other than recognizing it as a factor, but no numbers or whatsoever. I guess that a minilab tank size is expected, but they do come in different sizes (5-10L i think). Overreplenishing is mentioned as a problem. This is my main concern as my working tank will likely be small (1L) so as not too waste much when re-mixing new tanks (a tradeoff for consistency). If I were to replenish say 50ml for each roll as suggested by the technical sheet, I'm sure I'll have an overreplenished tank pretty soon. On the other hand, underreplenishment is obviously a problem, too. The developer is the only solution to be concerned. The one that's available where I live is one you get by mixing a starter with a replenisher that comes as a single solution, and water.

It seems that Fujifilm hasn't published a detailed guide as Kodak's old "131" pdf. There are a few guides they published, all of which I found incomplete, outdated, not meant for the exact same chemistry they sell today.

Before getting dissuasive advice I just want to say the following: I'm aware there are so many things to consider, so much to put together from the notes I've been taking during the past weeks before I proceed to buy the stuff. Perpetuating a working tank solution is not the plan, but a repetitive replenishing cycle for some time before mixing a new working tank is needed to make this economically feasible where I live (prices are 4x the US prices for this chemistry). I know there is no definitive guideline, and that exhaustive testing of solutions with test strips has to be done periodically to get consistent, high quality results. (Minilab tanks will deviate from acceptable concentrations even when following the datasheets by the letter and having a high throughput. If complete testing can't be run the best thing to do is to discard and mix new working tanks from time to time). I just need a good guess to start with, an educated guess for this 'replenishing rate:tank volume' ratio. I won't be using test strips and a densitometer, at most I will do pH and SpG metering. I don't expect optimal processing, though I want it to be quite good. To have my films processed by local labs is not only expensive, but unacceptable to my quality standards. There's really no other option than doing it myself. Rigorous storage of chemicals will be carried out. It is likely that the chemicals will be split between some friends and I so as not to waste much due to expiration and oxidation, and it's also likely for me to start offering film processing services where I live.

I'll be happy to share my procedure in detail if I get to make it work. Any help will be appreciated!

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Probably "everybody" has read the old Kodak opinion "do not attempt to replenish" when talking about using chemistry in tanks or in rotary processing. Their suggestion was using chemistry only one shot. My opinion on this matter is not so strict. I have been replenishing my RA.4 chemistry for years, with no ill effects. Of course, there are many things that matter, and I am not willing to write about every possible cause of trouble here. Using chemistry in manual or partially manual processing is always more or less finding a process that fits your equipment and other factors, and when it works, you should minimize all variations, and stick to your process. I don´t see any reason why C-41 can´t be replenished, if the output is enough for the system to work. Otherwise, I would suggest using the chemistry for a few times with slight extension of developing times. But the reuse must be moderate - not as the salesmen of some home kits suggest (20 rolls per liter or so), but in the range of 10-12 rolls, and probably not reusing more than thrice. All developers are pretty standard - only the replenishment rates vary. The biggest difference between "standard" and C-41RA (RANP and other variations included), is the use of more concentrated, fast bleach and a rapid fixer. Many variants also omit the wash between bleach and fix, but in exchange, need bigger replenishment rates for fixer. Also, wash with water is often replaced by different kinds of final rinse, such as Fuji Hunt´s Superflo, or the Fuji variant using chrorine tablets in water, and then a final rinse. Reason for this was enabling the use of minilabs without plumbing.

lamerko said:

As far as I understand, the minimum tank size that is given is 5 liters. Also, the amount of replenisher depends on both the area and the film material itself.
It seems that replenishment the developer at home is not appropriate.

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The 5 liter tank is the smallest used in minilabs, and Fuji TB are all meant for photofinishers - not for home users. This does not mean the minimum size of vessel is really 5L, where replenishment works. I am fully aware of the old Kodak opinion that replenishing small amounts "should not be attempted", but my own experience does not support fully this opinion. That said, oxidation is an issue that might affect the results. My best advice is trial and error. Something will work for your setting too, and I doubt that only one shot use would be possible.

Samu said:

I have been replenishing my RA.4 chemistry for years, with no ill effects

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Me too. RA4 is a totally different animal from C41 though. RA4 is pretty much a develop-to-completion process. C41 is nothing at all like that. Moreover, inter-layer effects such as color balance and acutance play a far different role in C41 (which is virtually always enlarged!) than in RA4 prints.
The fact that you can indeed quite successfully replenish RA4 developer in a home setting has no bearing whatsoever on the possibilities to do this with C41.

Samu said:

Otherwise, I would suggest using the chemistry for a few times with slight extension of developing times.

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Please refer to #3 and also @Mr Bill's comments. You may or may not be satisfied with re-using the same volume of developer. At some point, you're definitely not going to be satisfied; the point at which this happens is different for everybody.

Samu said:

oxidation is an issue

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And by far not the only one.

koraks said:

Me too. RA4 is a totally different animal from C41 though. RA4 is pretty much a develop-to-completion process. C41 is nothing at all like that. Moreover, inter-layer effects such as color balance and acutance play a far different role in C41 (which is virtually always enlarged!) than in RA4 prints.
The fact that you can indeed quite successfully replenish RA4 developer in a home setting has no bearing whatsoever on the possibilities to do this with C41.



Please refer to #3 and also @Mr Bill's comments. You may or may not be satisfied with re-using the same volume of developer. At some point, you're definitely not going to be satisfied; the point at which this happens is different for everybody.



And by far not the only one.

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As I said, there is not a definitive answer to the question. C-41 is different, and you would need to develop quite a lot to achieve the goal of replenishing half of your developer volume in about 3 weeks. With my RA-4 developing, this is really not a problem with Enviroprint 160 MP, which I am normally using. The ideal results in tanks or tubes are of course possible only with one shot use of the developer, but even the margins of "acceptable results" are quite broad in C-41. Often the problems with such things as inconsistent temperature or time have much larger effect than a moderate reuse of chemistry does. As I said, there is not a definite answer, and I don´t take also a Kodak publication from the 1960´s as a pure gold, when it writes "do not attempt to replenish". All of those home kits that I don´t use, are based on the same developers used in the industry, and all of the manufacturers of these products suggest reusing them - often to a degree that no developer can produce anything even vaguely resembling a good quality negative. I probably would agree with the instructions of Fuji Hunt 5L C-41 kit, which gives times for extended developing with reusing chemicals in moderation, but stating at the same time, that for perfect results, the developer should be used only once. Ruining a batch of 20 € films in order to save cents for developer costs is of course stupid.