Any sure way to tell if C-41 has gone bad?

stephsleeps · May 7, 2021

I have mixed C-41 that I used maybe 2 months ago.. kept in a cool place, air-tight.
I just opened up the developer and poured a little out and its still very light in color.

koraks · May 7, 2021

Besides testing with color densitometry there is no accurate way of verifying c41 developer activity. The fact that there has been little to no color change is promising however. I routinely use c41 developer that is many months old, but I make sure to store it in glass bottles that are filled to the brim and tightly capped. Oxygen is the enemy.

brbo · May 7, 2021

Should be good. I've used mixed and used C-41 developer stored in the same manner as you describe that was up to a year old and the negatives scanned and printed just fine.

pentaxuser · May 7, 2021

I take it there is no equivalent of the film leader check with a b&w developer that can be used with a C41 leader?

pentaxuser

Donald Qualls · May 7, 2021

pentaxuser said:
I take it there is no equivalent of the film leader check with a b&w developer that can be used with a C41 leader?

You can do that exact test, but all it will tell you is that the developer still has some amount of activity. The color process is critical of the rate of development vs. rate of gelatin penetration (this is why a few degrees temperature change causes crossover and casts), so a developer condition that, with B&W, would simply produce a negative with a slightly reduced contrast (still very printable and scannable), will produce crossover due to mismatched development rates of the layers.

Now, that said, I've been replenishing my Flexicolor for six months or so, through thirty-plus rolls, and the replenisher has been in a partially filled PET bottle all that time -- and as far as I can tell, my most recent color negatives were fine. I don't yet print RA-4, however, and apparently don't have a very critical eye for color, so others might disagree on my color condition.

Pitotshock · May 7, 2021

You could develop a roll of film like I did with some 4 month old Cinestill Cs41 and end up with a roll that looks like this!

A leader test would have avoided this failure, but maybe not prevented poorly developed images.
Coincidentally, I just uploaded a youtube video I did on this, just yesterday!

pentaxuser · May 7, 2021

Pitotshock said:
You could develop a roll of film like I did with some 4 month old Cinestill Cs41 and end up with a roll that looks like this!

View attachment 273843

A leader test would have avoided this failure, but maybe not prevented poorly developed images.
Coincidentally, I just uploaded a youtube video I did on this, just yesterday!

I watched your video and thanks for that and please take this in the context of wanting to learn from this but I had difficulty understanding your commentary at times when the end of a sentence seemed to tail off. It looked as if you had C41 that was known to be exhausted and some that was fresh. Into both you placed a leader and at the end of 2.5 mins it was clear to you that one had worked and the other hadn't and you asked if we could see the difference but unfortunately I couldn't see from the camera angle, nor could I work out what the blix did that indicated it was working also

Would it be possible to reveal or say what the difference was?

I am sure this could be a very good video and is of the kind that few if any have made and while I can only speak for myself, I think it could be improved in terms of a fuller explanation of what is being done, why it is being done and making sure the results are easier to see

Thanks

pentaxuser .

pentaxuser · May 7, 2021

Donald Qualls said:
You can do that exact test, but all it will tell you is that the developer still has some amount of activity. The color process is critical of the rate of development vs. rate of gelatin penetration (this is why a few degrees temperature change causes crossover and casts), so a developer condition that, with B&W, would simply produce a negative with a slightly reduced contrast (still very printable and scannable), will produce crossover due to mismatched development rates of the layers.

.

Donald, do I take it that the problems of which you speak will still occur at less than 100F and even if the test is done at 100F this makes no difference to the potential flaws in terms of mismatched development rates i.e such mismatches which occur with less than 100% effective C41 developer will still occur and will only be detectable when exposed frames are developed?

pentaxuser

Donald Qualls · May 7, 2021

Generally, you'll only be able to spot crossovers and casts when there are colors and contrasts to look at. Just developing an exposed 35mm leader proves almost nothing because all the layers are fully exposed, there are no tones that will tell you if one layer has a different contrast than another. So yes, an exposed frame (either an actual subject or a color test chart or Shirley) is necessary to be completely sure -- but if the leader turns black within a couple minutes at 100F, your developer is probably okay.

pentaxuser · May 7, 2021

Thanks Donald. So a fundamental flaw exists in a leader test of C41 for which there is no solution other than an exposed frame test. Even then how easy is it to see colour crossover in a 35mm neg or in fact is the test not complete until an RA4 print Is attempted?

pentaxuser

Donald Qualls · May 7, 2021

If you're looking for it, it's not hard to see crossover in a scan. At its core, it's a color cast you can't correct out. Usually it's a magenta cast on highlights, and a green cast in shadows. I'm not very good at seeing it, and/or it doesn't bother me much, but it is visible in scans.

In a scan, it's theoretically possible to improve it -- you can separate the color channels and individually adjust their curves, then recombine them -- but with overall filtration (as you'd use to correct color in printing) it's impossible to completely remove, and it's usually more work than it's worth in digital post.

pentaxuser · May 7, 2021

Donald Qualls said:
If you're looking for it, it's not hard to see crossover in a scan. At its core, it's a color cast you can't correct out. Usually it's a magenta cast on highlights, and a green cast in shadows. I'm not very good at seeing it, and/or it doesn't bother me much, but it is visible in scans.

In a scan, it's theoretically possible to improve it -- you can separate the color channels and individually adjust their curves, then recombine them -- but with overall filtration (as you'd use to correct color in printing) it's impossible to completely remove, and it's usually more work than it's worth in digital post.

Thanks. Looks like it would have to be an RA4 for me to discover if a crossover exists as I don't use a scanner

pentaxuser

cmacd123 · May 7, 2021

best test might be to make a close approximation of a processing test strip. (perhaps an accurately exposed couple of frames with a colour check chart and grey card.) and process that before running any "real" film.

Tel · May 7, 2021

Not sure which C-41 chemistry we're talking about here; I've only used Unicolor kits, both dry and liquid. But I routinely get 15-20 rolls per liter and often find the chemistry still works after six months or so. I store it in brown glass bottles, tightly capped and kept in a dark cupboard. And I've used the clip-test described above but only, as Donald noted, to check whether the chemicals are still active. I call it the "falling off the cliff" test because I've found that failure of the developer tends to happen suddenly and totally. Last month I was using some developer that I made up in October, so in its 6th month. One day it gave me a good clip test and I got decent results from a roll I'd shot, then a few days later it failed completely. Coincidentally, it had also turned nearly opaque between those tests. So if the stuff in question has been properly stored, is only two months old and the color looks good, it probably is good. Stretching your chems is a crap-shoot of a sort, because though they can still be good months after being mixed, they can fail very quickly when they do go bad.

koraks · May 8, 2021

Tel said:
I call it the "falling off the cliff" test because I've found that failure of the developer tends to happen suddenly and totally.

How do you verify the correct functioning of the developer just before it falls off the cliff? I mean the more subtle problems that may occur such as lack of contrast and crossover.

Pitotshock · May 8, 2021

pentaxuser said:
I watched your video and thanks for that

Thanks for the constructive feedback, I'll work on my Youtuber strategy a bit to get better!

Sirius Glass · May 8, 2021

I save up my film until I have 12 to 16 rolls and then mix up the C-41 kit. I develop in two or three days and then dump the chemicals.

pentaxuser · May 8, 2021

Pitotshock said:
Thanks for the constructive feedback, I'll work on my Youtuber strategy a bit to get better!

Thanks for the response. I always feel that we owe it to any video presenter to say if there were parts that we find difficult to follow, especially when the video is valuable. I always think of YouTube videos from Photrio members to be the equivalent of a kind of mutual benefit society. The presenters want to be of service to us and we want to understand everything that is being presented. A win-win situation

pentaxuser

Tel · May 8, 2021

koraks said:
How do you verify the correct functioning of the developer just before it falls off the cliff? I mean the more subtle problems that may occur such as lack of contrast and crossover.

Well, that's the crapshoot part. If I've got a roll of shots I don't want to lose, I'll err on the side of caution and mix up a new batch. (It's not THAT expensive compared to using a lab...) I pay attention to the color of the developer and I keep careful track of the time since I mixed the chemicals. If I suspect an imminent failure and it's a roll or rolls I don't want to take a chance with, I'll dump it and make a new batch. I've never dumped a batch after fewer than 12 rolls, except one time when I got sloppy and contaminated with some blix. Never doing that again!

Donald Qualls · May 9, 2021

cmacd123 said:
best test might be to make a close approximation of a processing test strip. (perhaps an accurately exposed couple of frames with a colour check chart and grey card.) and process that before running any "real" film.

But unless you have some accurate means to read the ersatz test strip, you're back to eyeballing a negative -- and unless you've processed negatives daily for many years, and then printed the results, I'd be amazed if you can look at a negative and see a moderate cast, never mind a crossover.

Any sure way to tell if C-41 has gone bad?

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