Reusing C41 Chemicals

Hi all,

Even though I'm sure this has been covered, I feel like I'm so new that a lot of the names and terms don't fully click. I am interested in developing my own C41 film, reading instructions seems to indicate that each kit will develop 16 rolls, though many people develop more than 16 rolls with a kit. What I am wondering is if each chemical is only good for 16 rolls? Meaning that each chemical has the exact lifespan as the others? Or can I actually get 40 rolls from Blix, 60 rolls from the stabilizer and 16 rolls from the developer(Just an example). Thanks everyone=D

There is no cliff you are going to fall of if you overuse your chems. They will become weaker, so you need to develop longer, your color balance will be off (which can be corrected if you scan), but overall you will get mostly usable negatives even with heavy reuse of chems.

JayBird said:

What I am wondering is if each chemical is only good for 16 rolls? Meaning that each chemical has the exact lifespan as the others?

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Well, the real situation is much more complicated than you might think, and the idea of a specific lifespan is not as exacting as you might think. It's pretty much like Rudeofus says, but if you don't understand things on a bit deeper level then you're best off just sticking to the manufacturer's instructions. They will mostly keep you from getting into too much of a problem.

If you want a little more insight, here's roughly how the developer works: one of the components is an actual "developing agent," in a specific concentration. There is also a "restrainer" which sort of holds back the development. The two work together to give a more or less balanced amount of development. Now, when you actually develop film, the developing agent is "used up" (destroyed) in proportion to the actual amount of development. At the same time, a byproduct of development is released from the film in the same proportions, and this byproduct IS a restrainer. So there is a sort of "double whammy" effect going on, but it depends on the degree of development. If your film is heavily exposed, such as photographing white objects, then the effect is very strong, and the allowable number of rolls is less. On the other hand, if the film is barely exposed, with near-black backgrounds, then the developer is barely used, so it could handle more rolls.

An additional complication is that the developing agent is also depleted by exposure to air. So simply letting the developer be handled gradually "kills" it, even if no development is being done.

So the bottom line is that the ability to do multiple rolls from a certain amount of developer is based on having some sort of tolerance in the quality of development, along with the ability to partially compensate by increasing the development time. If a certain manufacturer says you can do more rolls with their developer, this means that they either have sloppier tolerances, or they presume a lesser exposure on the film.

In professional photofinishing, which I have been involved with, we don't work with such loose tolerances. For each roll we develop, we add a small amount of a "developer replenisher" solutions which counteracts the tendency for the developer to become worn out, so that it always stays at the same strength (within some tolerance). So you can see that this whole concept of "lifespan" of a developer is an inexact sort of thing, and it largely depends on how finicky you are - at what point does the off-spec development really start to bother you?

In the case of "blix," where the bleach and fix are combined, the way it "wears out" is somewhat different than the developer. Additionally, the two parts mixed together are sort of mutually self-destructive, so it's probably more important to use it within a shorter period of time than to be too concerned about the roll capacity.

Anyway, the bottom line is what's good enough for your purposes, and sticking with the manufacturer's instructions will likely help keep you there. You might note that Kodak's guidelines probably don't let you do as many rolls as some other makers; this is not so much due to any magical properties, but rather that Kodak is more conservative with helping you stay out of trouble.

Hope this is a little bit useful to you.

I purchased my three c-41 1L press kits from BH. They used to ship them. Must be five years ago. My first kit lasted two years. I dumped it after 25 rolls, just because. I think, I'm close to one year with second kit.
And third one not even open.
If you are using tiny developing tanks it will last longer. I'm using two reels tanks and it is getting to the point then it is not enough in the bottle. Due to spills at each developing.

Rudeofus said:

your color balance will be off (which can be corrected if you scan)

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you can correct colour balance in the darkroom too

If there is crossover or retained silver due to re-use, that may be difficult to correct even if you scan.

A scanned photo can be fully restored as long as the three characteristic curves are strictly monotonic with respect to, and sufficiently selective to incoming light of their respective wavelength. Things are a bit more complicated with optical prints, where even mild color crossover can hurt results. Yes, if really only color balance is off, i.e. all three characteristic curves have the exact same slope but their y-offset is off, then you can fix the image even with wet printing. The chances of this happening with off-chemistry are not very high, though.

RPC said:

If there is crossover or retained silver due to re-use, that may be difficult to correct even if you scan.

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when I say "re-use" I mean within the limits suggested by the producer. in my case I process 10 rolls with 1L and discard. It is very unlikely to get unusable negatives.

Berri said:

when I say "re-use" I mean within the limits suggested by the producer. in my case I process 10 rolls with 1L and discard. It is very unlikely to get unusable negatives.

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Whether they are unusable depends upon the user. Personally, I would not trust the limit figures of this manufacturer unless I had tested for crossover and retained silver or at least done visual comparisons. Some manufacturers advocate low temperature processing, for example, but that does not give acceptable images to me. So I would not trust a manufacturer until I had run tests. YMMV.

I optically print and want my negatives to be right. But even if I scanned, I would still want them to be technically correct,
as I see no point in having to go to the trouble of correcting them with software.

Berri said:

when I say "re-use" I mean within the limits suggested by the producer. in my case I process 10 rolls with 1L and discard. It is very unlikely to get unusable negatives.

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RPC said:

Whether they are unusable depends upon the user. Personally, I would not trust the limit figures of this manufacturer unless I had tested for crossover and retained silver or at least done visual comparisons.

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Kodak's Z manual suggests either 3 or 4 rolls per liter, depending on the film type. I would generally feel comfortable with Kodak recs, given that they tend to be more conservative. But my main experience has been in labs where we wouldn't even consider "batch" use; everything was replenished. In my experience this is the best way to keep tight control of development - slight differences between developer mixes get "damped out" in the processor. But you need enough volume to make this sensible.

In the end, it depends on what works for you, I guess. In our labs handling a large portrait studio chain, I doubt we could have tolerated even Kodak's more limited usage. Mainly because of the logistics of an optical printing system back in the day, not necessarily crossovers, etc. But today, in the age of scanning, probably anything is "fixable," depending on how finicky you are, and how much time you're willing to put into it.

The more rolls you process, the more contamination of chemicals you will have, both from bromide released from the film and carryover from each step. This could cause a color crossover, larger grain and blocked highlights. You can technically get more rolls out of the kit, perhaps twice as many, but if you care about the colors and grain I would say avoid doing so. Especially if you want to print them in the darkroom. It's worth it in my opinion to use fresh chemicals. To extend the life of your kit, use a pre-wash and wash between each step. But try not t go too much farther than 50% recommended capacity. And if you have the money, just get a fresh kit.

Note that this is all regurgitation of stuff posted here by seasoned members but I have asked the same question.

RPC said:

I optically print and want my negatives to be right.

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I optically print too ande my negatives are right. Do you process one shot? What chemicals do you use? Even if you do it one shot the only acceptable way to determine the actual quality is by using a densitometer and test strips, do you do this?

If you get Kodak's minilab chems in large batches, then single use processing or a limit of 3-4 rolls per liter may be feasible. With Tetenal's pricing this is not the case, though. As indicated by Tetenal's manuals, their chems are made for reuse.

I’ve had good results with the Arista liquid kit from Freestyle reusing the chems as recomended up to the capacity noted on the instructions. I also optically print and have found results to be consistent enough that I don’t encounter any problems. Color correction will vary a few units when printing, but I expect that from the many variables that exist before I get to view a final print (film batch/storage, paper batch, film chems/print chems, phase of the moon, etc, etc).

Berri said:

I optically print too ande my negatives are right. Do you process one shot? What chemicals do you use? Even if you do it one shot the only acceptable way to determine the actual quality is by using a densitometer and test strips, do you do this?

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I use one-shot for developer but reuse bleach and fix once. I use Kodak developer and fixer, and a ferricyanide bleach. I can also mix developer from scratch chems with formulas.

I use a densitometer, an x-rite 810, but do not use official test trips. Instead I shoot a gray scale on each roll, take density readings on the negatives and can plot the curves for parallelness to check for processing errors. Using specific density patches from the gray scale I can also do HD-LD readings, like with a control strip. It's easier than plotting but does not show as much curve information. How do you check your negatives to know they are right?

RPC said:

I use one-shot for developer but reuse bleach and fix once. I use Kodak developer and fixer, and a ferricyanide bleach. I can also mix developer from scratch chems with formulas.

I use a densitometer, an x-rite 810, but do not use official test trips. Instead I shoot a gray scale on each roll, take density readings on the negatives and can plot the curves for parallelness to check for processing errors. Using specific density patches from the gray scale I can also do HD-LD readings, like with a control strip. It's easier than plotting but does not show as much curve information. How do you check your negatives to know they are right?

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If I'm happy with the prints I get and the photos I take, then my negatives ARE right.

Berri said:

If I'm happy with the prints I get and the photos I take, then my negatives ARE right.

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Well, that's fine. But nevertheless, there maybe some out there who think they are getting optimal results but upon doing meaningful tests, discover they are not, such as with the re-use of the chems discussed here, as well as low temperature processing, and that may important to them. That is why they should be forewarned of the possibility.

RPC said:

Well, that's fine. But nevertheless, there maybe some out there who think they are getting optimal results but upon doing meaningful tests, discover they are not, such as with the re-use of the chems discussed here, as well as low temperature processing, and that may important to them. That is why they should be forewarned of the possibility.

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true. Even though I do not own a densitometer I check my negatives for consistency by means of a color analyzer (colorstar 2000) and the balancing of grey card it it doesn't float too much from what is expected. I keep the temperature at 38°C with a thermostatic bath (checking the temperature through all the process inside the tank). I use Bellini C41 kit and never process more than 10 rolls in 1 month and my negatives are easy to print delivering goor results as I would expect from fresh films. If I had a densitometer I would probably go the replenishing route, not one shot, because too fresh dev could produce too dense negatives

Berri said:

If I had a densitometer I would probably go the replenishing route, not one shot, because too fresh dev could produce too dense negatives

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Fresh and properly replenished developer should both give in-spec results. I know this is a fact because I worked at a lab that ran control strips. The replenishment keeps the developer as fresh, although there may be very slight differences. If replenisher is used to make developer as labs do, then the addition of what is known as "starter" is added when mixing the developer to give proper results. Without it the negatives could be too dense. Perhaps that is what you are thinking of. Standard developer requires no starter and gives results the same as replenisher with starter, or properly replenished developer. Thus, doing one-shot development is never an issue. On the other hand, re-using developer is when replenishment should be considered.

RPC said:

Fresh and properly replenished developer should both give in-spec results. I know this is a fact because I worked at a lab that ran control strips. The replenishment keeps the developer as fresh, although there may be very slight differences. If replenisher is used to make developer as labs do, then the addition of what is known as "starter" is added when mixing the developer to give proper results. Without it the negatives could be too dense. Perhaps that is what you are thinking of. Standard developer requires no starter and gives results the same as replenisher with starter, or properly replenished developer. Thus, doing one-shot development is never an issue. On the other hand, re-using developer is when replenishment should be considered.

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one shot is too expansive and honestly I don't see the point in using a densitometer on a negative; if the density is off or there are othere issues you have either lost your photos or get bad results. While for me the prints I get are the only judge. I could buy fuji cemistry and test strips but as I said I don't have a densitometer so it wouldn't make any sense. Did you ever try to reuse a kit like Bellini or Tetenal?

Berri said:

... honestly I don't see the point in using a densitometer on a negative; if the density is off or there are othere issues you have either lost your photos or get bad results.

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Well, what RPC is referring to is not just some ambiguous point on the negative, but at least two points where the relative exposure difference is known. So that one can say, ok this is the density difference per such and such an exposure change; in other words, a measure of "contrast." This is essentially a measure of the "strength" of the development.

You ARE right that by this time any damage has already been done, and you can't undo a development problem. So in this case, the only value is to know what is the reason for your hard-to-print negatives, or whatever. But if the actual problem is overuse of the developer, then hopefully the PRIOR test roll would have shown a more moderate stage of the problem, and you might have never developed the "bad" roll.

By the way, I spent a number of years in a large lab running roughly 40 to 50 process control strips per day (although the vast majority were for paper processors, not film), and have been involved in pretty extensive paper and film testing. So I've been around the block, so to speak, and would like to say that RPC is giving some pretty good info. Btw, I would also say that the quality of the final images is really the final arbiter; using control strips and thermometers and timers, etc., is just a way to give you some control over the process in an attempt to meet the manufacturer's specifications. I'm not saying that this is worth the trouble for everyone, but it's a pretty reliable way to help keep one's quality levels consistent.

In HD-LD measurements, two specific points can give you the contrast as Mr. Bill says, and the correct densitometer can measure it for all three primary colors, and you can then determine the degree of crossover, if any. And as I said earlier it is possible to plot the complete curves for each of the three colors and give a more detailed view of your processing results.

It is a great way to determine how much re-use one could do before results become non-optimal (technically) if one desires to know that.

If one lacks a densitometer then the next best think would be to shoot (exposed properly) and print a gray scale. If it can be color balanced so the gray patches match or are very close to the original, then crossover can be disregarded. A noticeable shift in color along the scale would indicate some. Of course this depends on your print process being accurate.

Mr Bill said:

Well, what RPC is referring to is not just some ambiguous point on the negative, but at least two points where the relative exposure difference is known. So that one can say, ok this is the density difference per such and such an exposure change; in other words, a measure of "contrast." This is essentially a measure of the "strength" of the development.

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I got that. But if the negative in that place is off due to bad developer all the other pictures will be off too, or not?

Mr Bill said:

then hopefully the PRIOR test roll would have shown a more moderate stage of the problem,

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that is why they invented control strips. Ther trouble shooting guide lines to overcome problems in the test strips.