Diluting C-41 very slightly to make up for lost volume -- question

RLangham · Mar 27, 2020

So I have a quart kit of C-41, almost depleted. I'm looking to develop two rolls today or tomorrow, before I can get a new kit. But I have a problem. Early in the lifetime of the kit, I spilled some developer, so that I had about 24 oz. left. I've been using it steadily, first in my Yankee Clipper II and then in a Paterson with two 35mm reels that a forum member kindly gifted me.

The problem is, some of the volume gets left on the film with each pair of rolls I develop, and now the volume of developer I have left has dipped just slightly below 20 oz. 20 oz. is the minimum processing volume for two rolls of 35mm in this Paterson. Obviously, I can add just a tiny bit of distilled water to bring it back up to 20 oz. My question is, what percentage should I add to the development time to compensate for the slight dilution?

(And yes, I know I could do the rolls in sequence, but these chemicals are approaching depletion and I'd rather do them both and spread what strength the developer has evenly across both, rather than have one get a better development than the other.)

afriman · Mar 28, 2020

Seeing as it has "dipped just slightly below 20 oz." the chances are there is probably still enough to cover the two rolls of film. I would suggest checking this with an equal volume of water in the tank with the two empty reels. As long as the top reel is covered, you have enough solution.

If you do need to top it up with just a very small amount of water, I doubt it would make any discernible difference even if you stick to the standard developing time. Maybe you can add five or ten seconds to compensate.

koraks · Mar 28, 2020

afriman said:
If you do need to top it up with just a very small amount of water, I doubt it would make any discernible difference even if you stick to the standard developing time.

Most likely. If this developer has already been used several times, odds are that depletion either due to oxidation or just the use itself will be a bigger factor than a marginal dilution.

RLangham · Mar 28, 2020

Well, thank you for your responses. I ended up doing them separately. I do think it's funny that you say, Koraks, "if the developer has already been used several times." This last one was roll twenty, on a kit that is said to be good for twelve or less.

Yes, the quality has just begun to go and I'll shortly order another kit.

Truzi · Mar 28, 2020

Actually, I think it's good you did them separately. I understand you wanted to spread "what strength the developer has evenly across both," but if the developer was too depleted, at least you would have had one well-developed roll instead of two poorly developed rolls.

I'm glad it worked out for both this way.

Rudeofus · Mar 28, 2020

In case you want to stretch your color chemistry much, much further, without sacrificing too much quality, take a close look at David Lyga's posting here. Some people in that thread are less than impressed with the test results, but these people generally use their chems single shot, which does not seem to be the case with you.

RLangham · Mar 28, 2020

Truzi said:
Actually, I think it's good you did them separately. I understand you wanted to spread "what strength the developer has evenly across both," but if the developer was too depleted, at least you would have had one well-developed roll instead of two poorly developed rolls.

I'm glad it worked out for both this way.

I did end up under-exposing the main roll I wanted to do, but it developed well enough.

Thing was, I have a modern Alkali cell in my old Nikkormat, such that the exposure is off by a stop and half from whatever ASA you set on the clumsy little slider at the bottom of the lens mount. I misread it, and it was set to properly expose 400 ASA, not 200 ASA, which is what I was rating the (expired) film at. Then of course, I had forgotten that I was previously rating that film at 100 ASA. Very thin negs, and I'm sure depletion played a role, especially in a mild color shift I observed (muted colors) but underexposure seems to be the main factor.

RLangham · Mar 28, 2020

Rudeofus said:
In case you want to stretch your color chemistry much, much further, without sacrificing too much quality, take a close look at David Lyga's posting here. Some people in that thread are less than impressed with the test results, but these people generally use their chems single shot, which does not seem to be the case with you.

Hmm... his methodology may be the way I go in the future. Pott ferri is the only expensive part of his method, huh?

Rudeofus · Mar 28, 2020

Is Potassium Ferricyanide really that expensive ? Isn't is possible to replenish such a bleach with Potassium Bromide and maybe some acid, since the Ferricyanide is restored through aeration?

RLangham · Mar 28, 2020

Rudeofus said:
Is Potassium Ferricyanide really that expensive ? Isn't is possible to replenish such a bleach with Potassium Bromide and maybe some acid, since the Ferricyanide is restored through aeration?

I dont know. I just know that it's a specialty chemical and most specialty chemicals I've looked into have been steep to my taste.

Rudeofus · Mar 29, 2020

RLangham said:
I dont know. I just know that it's a specialty chemical and most specialty chemicals I've looked into have been steep to my taste.

Potassium Ferricyanide shouldn't be a specialty compound. Check with a local pharmacy whether they have it. More often than not shipping cost make up the largest part of the cost.

Donald Qualls · Mar 29, 2020

@RLangham You should be able to buy potassium ferricyanide from any of the alt-process photo chemical suppliers, like Formulary or Artcraft -- it's the core of Farmer's Reducer, so worst case you could buy the Formulary kit for that and keep the thiosulfate crystals to make plain hyp fixer. It's also the bleach for color toning and sufide sepia toning of prints.

RLangham · Mar 29, 2020

Donald Qualls said:
@RLangham You should be able to buy potassium ferricyanide from any of the alt-process photo chemical suppliers, like Formulary or Artcraft -- it's the core of Farmer's Reducer, so worst case you could buy the Formulary kit for that and keep the thiosulfate crystals to make plain hyp fixer. It's also the bleach for color toning and sufide sepia toning of prints.

I think that's what I'll eventually do. Thanks, Donald!

Diluting C-41 very slightly to make up for lost volume -- question

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