C41 Bleach Formula?

fdonadio · Jul 15, 2020

Jemzyboz said:
Hi Photo Engineer,

I've been hunting around and there are so many different bleach formulae for bleach, multiple published by you. I was wondering which of yours you would say is the most updated one. And would you find the ferricyanide bleach formulae inferior in results to an ammonium FeIII EDTA based bleach?

Jemzyboz,

I’m sorry to say that, but Ron (a.k.a. Photo Engineer) won’t answer your post, as he passed away early this year, unfortunately.

I am definitely not an authority, but I dare say the ferricyanide bleach is just as good, but will give you more work, as stated by Ron. You need to use a clearing batch (sulfite solution) and wash thoroughly to avoid contaminating the fixer. There’s also the Prussian blue formation as the ferri bleach gets spent.

I am sure modern formulations use Ferric-Ammonium PDTA. Ferric Ammonium EDTA is an easier to find alternative that is as convenient (doesn’t require a clearing bath) as the modern stuff, but not as strong.

I believe PE posted a procedure for making Ferric Ammonium EDTA from EDTA free acid, Ferric Nitrate and Ammonia solution, which are easier to find than the readymade compound. I might have it on my computer. If you can’t find it here, just let me know.

—
Flavio

Jemzyboz · Jul 15, 2020

I'm very sorry to hear that Flavio I assume you knew him so my condolences to you and his family.

If you have the latest formula, please let me know, I'm not able to get the PDTA version as I'm in the UK but I have access to EDTA.

How strong should the sulphite solution be? 10%? Can I mix it into the stop bath in between the developing and ferricyanide bleach? I'm quite new to making C41 chemicals. My only experience has been making BnW chemicals. I plan on using the ferricyanide bleach one shot as I use a Jobo if I go ahead with that bleach.

I would like to experiment with both types of bleaches. I remember reading somewhere Ron mentioning that to replenish the ammonium FeIII EDTA based bleach, you have to replenish via ammonium bromide as well as the aeration. He didn't state the quantities to replenish however

RPC · Jul 16, 2020

Here are links to recent threads which include discussions on ferricyanide bleach:

https://www.photrio.com/forum/threads/guidance-on-managing-basic-ph-in-homebrew-chemistry.176531/
https://www.photrio.com/forum/threads/does-ferricyanide-bleach-exhaust-if-so-when.176529/

A ferricyanide bleach works as well or better than standard bleach and is more economical.

fdonadio · Jul 16, 2020

Jemzyboz,

I didn't know him personally, but used to talk to him through private messages and on the forums. He was such a nice guy that I feel I've known him forever. I planned to visit him when I went to the USA again, but I didn't get a chance.

The most recent C-41 formula posted by @Photo Engineer, I think, is here. The bleach formula is reproduced below:

Here goes the procedures as I found them here on Photrio (UNTESTED):

How to Make Ferric Ammonium EDTA from EDTA Free Acid (original post by PE here):

1 Mole - EDTA (free acid)
4 Moles - 28% Ammonium Hydroxide
1 Mole - Ferric Chloride (FeCl3)

Mix and add a 10% excess of EDTA. And, use caution: the 28% Ammonium Hydroxide is nasty stuff.

How to Make EDTA Free Acid from Dissodium EDTA (original post by @Rudeofus here)

Dissodium EDTA
Sulfuric or Hydrochloric Acid

Dissolve as much EDTA-Na2 as possible in a liter of water. Add a strong acid like Sulfuric Acid or Hydrochloric Acid. As long as the acid is strong enough, EDTA free acid will precipitate, because it's barely water soluble. Add acid ling enough to precipitate all the EDTA, then filter and wash the precipitate. After the precipitate is dry, which takes a few days, you can use it as EDTA free acid.

The clearing bath is a 1% Sodium Sulfite solution. Here's what @RPC has said in another thread:

If you use the clearing bath I would use a minimum of 1 minute wash after the bleach, 1 minute clearing bath (10 grams/liter of sodium sulfite), and another wash of 1 minute before the fixer. All washes are running-water.

We lack lots of information. Replenishers and replenishment regimes are only some of them. In fact, I have used Kodak Flexicolor chemicals for some time now and stopped trying to make my own because it's really not worth it. Only thing I would like to know is what (and especially how much) goes in C-41 Developer Part C, since it's the first thing to go bad in a C-41 kit. Everything else looks to be imperishable.

Good luck with your endeavour.

--
Flavio

RPC · Jul 16, 2020

fdonadio said:
Only thing I would like to know is what (and especially how much) goes in C-41 Developer Part C, since it's the first thing to go bad in a C-41 kit.

Part C is the developing agent, CD-4. Typical C-41 developer formulas call for about 4.5-5 grams/liter of CD-4. There is usually something added as to well to the bottle to help preserve its shelf-life, such as bisulfite, by making it slightly acidic. This would likely have an affect on the overall pH of the mixed developer, and since I don't know exactly how much is in there, checking and adjusting the pH if necessary after mixing should be done for ideal results. Otherwise the results could be slightly contrasty due to slightly high pH. Shoot for a developer pH of about 10.1 for normal results.

I have had Part C go bad and replaced it with CD-4 as described with excellent results.

fdonadio · Jul 17, 2020

RPC said:
Part C is the developing agent, CD-4. Typical C-41 developer formulas call for about 4.5-5 grams/liter of CD-4.

Makes perfect sense! The formula posted by Photo Engineer specifies 4.52g of CD4 per liter. If there’s nothing really important in part C, like Hydroxylamine Sulphate, it’s OK to just add the CD4 and adjust the pH.

Thanks!

—
Flavio

RPC · Jul 17, 2020

Part B--that's the hydroxylamine sulfate (preservative after mixing).

fdonadio · Jul 17, 2020

RPC said:
Part B--that's the hydroxylamine sulfate (preservative after mixing).

I have just overcame my laziness and searched for the MSDS. Strange thing is that Kodak now has a system where you must request the desired MSDSs; they're not freely available for anyone to download.

I have found the right MSDS for the CAT # I use, which is 823 1672 (KODAK FLEXICOLOR LU Developer Replenisher LORR). It says:

Weight percent	Components - (CAS-No.)
35 - 50	4-(N-ethyl-N-2-hydroxyethyl)-2-methylphenylenediamine sulfate (25646-77-9)
1 - 5	Sodium bisulfite (7631-90-5)

The part C bottle contains 56 mL (0.056 L). This, along with the other parts and some water, makes 5 liters of developer replenisher. So, based on the 4.52 to 5 g/L figure, we should have between 22.6 and 25 g of CD-4 in there. We don't know which solvent is used, but if it's water, it puts the weight percent at 40.36 to 44.64, well inside the range in the MSDS.

About the needed amount of bisulfite, the MSDS says — of course, we're talking about the concentrate in the part C bottle — the pH should be 2.1. It's not slightly acidic, it's very acidic! Then I guess CD-4 is acidic by itself, as bisulfite alone definitely can't bring the pH of a neutral solution down to 2.1 in the 1 to 5 % weight percent range. If there was any other acid in part C, it would certainly be on the MSDS, right?

Well, I guess my investigative skills have been put to good use today.

EDIT: if this chinese company is to be trusted (why not?), CD-4 has a pH range of 2.1 to 2.50. So, when diluted, the pH should go a little up and only a small amount of bisulfite is needed to bring it down.

RPC · Jul 17, 2020

I never realized Part C was that acidic. I remember now PE said the space in the bottle was filled with sulfur dioxide but I would think that would have little if any effect on the pH of the liquid.

koraks · Jul 18, 2020

CD4 is indeed acidic. If you dissolve CD4 powder in an alkaline solution, it fizzes like mad.

RPC · Jul 18, 2020

I'm not surprised it is acidic, I think many developing agents are, but I didn't realize it was so acidic. I wonder then, just what the degree of importance of the bisulfite is in Part C. Apparently enough for Kodak to add it to extend shelf life; I have never seen it in any formula.

Anon Ymous · Jul 18, 2020

RPC said:
I'm not surprised it is acidic, I think many developing agents are, but I didn't realize it was so acidic. I wonder then, just what the degree of importance of the bisulfite is in Part C. Apparently enough for Kodak to add it to extend shelf life; I have never seen it in any formula.

Yes, it's only there to keep CD4 from oxidising. Sodium bisulfite and metabisulfite are practically the same and metabisulfite is one ingredient in the CD4 formula posted by PE at the thread that @fdonadio linked to earlier. Surprisingly, the formula lists both sulfite and metabisulfite. Perhaps the metabisulfite level in the formula hints to its concentration in the part C bottle?

RPC · Jul 18, 2020

Anon Ymous said:
Surprisingly, the formula lists both sulfite and metabisulfite. Perhaps the metabisulfite level in the formula hints to its concentration in the part C bottle?

Could be.

I know that sulfite affects dye formation so maybe it is there to precisely control it?

koraks · Jul 18, 2020

As I understand, any bisulfite will effectively convert into sulfite in the alkaline environment of a developer. So I would suppose they could be applied interchangeably with regard to stoichiometry.

Anon Ymous · Jul 18, 2020

koraks said:
As I understand, any bisulfite will effectively convert into sulfite in the alkaline environment of a developer. So I would suppose they could be applied interchangeably with regard to stoichiometry.

Exactly, there's a lot of carbonate in this developer and when adding metabisulfite it instantly becomes sulfite, while carbon dioxide is released with fizzing.

RPC · Jul 18, 2020

So the question is, why both sulfite and metabisulfite in the formula. Couldn't it be made simpler it by eliminating the metabisulfite and adjusting the level of sulfite.

Rudeofus · Jul 24, 2020

The Sulfite does two things: it scavenges Oxygen and thereby protects the developer from oxidation, but it also reduces negative contrast, because sulfite ion reacts with oxidized color developer and thereby reduces amount of dye formed during development.

There is a small and well controlled amount of sulfite in C-41 color developer. If you keep sulfite in a bottle in very acidic conditions (such as those in C-41 CD part C), a sizable amount will be present as Sulfur Dioxide. You certainly do not want that 56ml bottle to contain 1-2 grams of Sulfur Dioxide. Therefore Kodak (and all the other makers of C-41 kits) are well advised to use 1-2 grams of Sodium Sulfite in C-41 part A, and only trace amounts of Sodium Metabisulfite in part C.

Jemzyboz · Aug 6, 2020

fdonadio said:
Jemzyboz,

I didn't know him personally, but used to talk to him through private messages and on the forums. He was such a nice guy that I feel I've known him forever. I planned to visit him when I went to the USA again, but I didn't get a chance.

The most recent C-41 formula posted by @Photo Engineer, I think, is here. The bleach formula is reproduced below:

Here goes the procedures as I found them here on Photrio (UNTESTED):

How to Make Ferric Ammonium EDTA from EDTA Free Acid (original post by PE here):

1 Mole - EDTA (free acid)
4 Moles - 28% Ammonium Hydroxide
1 Mole - Ferric Chloride (FeCl3)

Mix and add a 10% excess of EDTA. And, use caution: the 28% Ammonium Hydroxide is nasty stuff.

How to Make EDTA Free Acid from Dissodium EDTA (original post by @Rudeofus here)

Dissodium EDTA
Sulfuric or Hydrochloric Acid

Dissolve as much EDTA-Na2 as possible in a liter of water. Add a strong acid like Sulfuric Acid or Hydrochloric Acid. As long as the acid is strong enough, EDTA free acid will precipitate, because it's barely water soluble. Add acid ling enough to precipitate all the EDTA, then filter and wash the precipitate. After the precipitate is dry, which takes a few days, you can use it as EDTA free acid.

The clearing bath is a 1% Sodium Sulfite solution. Here's what @RPC has said in another thread:

We lack lots of information. Replenishers and replenishment regimes are only some of them. In fact, I have used Kodak Flexicolor chemicals for some time now and stopped trying to make my own because it's really not worth it. Only thing I would like to know is what (and especially how much) goes in C-41 Developer Part C, since it's the first thing to go bad in a C-41 kit. Everything else looks to be imperishable.

Good luck with your endeavour.

--
Flavio

Thanks Flavio, yeah this looks insanely expensive to make... plus I don't think I can get half of these ingredients... I think I will stick to my homemade developer and a simple fixer Ron posted in the past and buy the Kodak bleach premade.

fdonadio · Aug 6, 2020

Jemzyboz said:
Thanks Flavio, yeah this looks insanely expensive to make... plus I don't think I can get half of these ingredients... I think I will stick to my homemade developer and a simple fixer Ron posted in the past and buy the Kodak bleach premade.

It’s cheap, takes ages to go bad and works, so why not?

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