C-42 is Kodak's home-version of C-41?

albada · Apr 13, 2012

Grant Haist is still alive, and he is selling new copies of his two-volume set, Modern Photographic Processing. Go to Dead Link Removed for more info.

I was reading the color chapter of my new books last night and noticed this in the C-41 section: "These same films [for C-41] can be processed in Process C-42, an official Kodak recommended process for Kodacolor II and Kodak Vericolor II films." And he gives the formulas for developer, bleach , fixer, and stabilizer. Here's the formula for the C-42 developer (vol 2, page 597):

Water ................................................ 800 ml
Potassium carbonate anhy ............... 37.5 g
Sodium sulfite anhy .......................... 4.25 g
Potassium iodide .............................. 0.002 g
Sodium bromide ............................... 1.3 g
Hydroxylamine sulfate (HAS) ........... 2.0 g
Kodak Anti-Calcium No. 3 ................ 2.5 g
CD-4 ................................................. 4.75 g
Water to make .................................. 1 litre

pH = 10.00 +/- 0.03. Add potassium hydroxide (10%) or sulfuric acid (10%) to adjust pH.

Except for insignificant rounding differences, the formula above is identical to the "official" C-41 formula posted by Gerald Koch (there was a url link here which no longer exists).

Although the pH should be 10.00, RPC reports that the pH comes out to 10.4-10.5, and that he adds white vinegar to adjust pH. See this thread: (there was a url link here which no longer exists)

All this leads to a question:
Why did Kodak publish a formula that gives the wrong pH? Or did Haist publish it with an error? Or is antical #3 a strong acid so that omitting it (as RPC did) causes this large pH-shift? For that matter, does anyone have information on the C-42 process? My internet search turned up nothing.

Thanks,

Mark Overton

RPC · Apr 14, 2012

I never new the ultimate source of that formula, I think I found it on the Gerald Koch post you mentioned. I am no chemist, just a darkroom enthusiast but in response to your pH question, it is common practise to adjust the pH of color formulas to adjust for contrast and parallel curves. Formulations aren't usually exact, pH-wise, as water pH may vary, even distilled, which I use, unless corrected for in the formula. The results I got were mine, yours and other's experiences may differ.

I never tried sulfuric acid to adjust the pH but it is better to use 28% or glacial acetic acid instead of white vinegar, that is what I use now, as it took me a lot of white vinegar to adjust it and that causes a slight dilution of the developer.

I have found an alternate formula from a patent:

Water (distilled) 800.0 mL
Potassium Carbonate 34.30 g
Potassium bicarbonate 2.32 g
Sodium sulfite, anhydrous 0.38 g
Sodium metabisulfite 2.96 g
Potassium Iodide 1.20 mg
Sodium Bromide 1.31 g
Hydroxylamine Sulfate 2.41 g
CD-4 4.52 g
Water to make 1 liter

Adjust pH

In my experience the mask color seems to more closely match Kodak C-41 negs than the developer you mentioned and required less pH adjustment.

Another poster on APUG, Stefan4u has posted a formula he concocted he calls C-27 which I have not tried but other APUG members have and claim it works very well.

albada · Apr 14, 2012

The fact that you had to add so much acetic acid makes me suspect even more strongly that something is wrong with that C-42 formula I posted. I can't believe that acids and alkalis would have that much variation in strength.

RPC said:
I have found an alternate formula from a patent:
Water (distilled) 800.0 mL
Potassium Carbonate 34.30 g
Potassium bicarbonate 2.32 g
Sodium sulfite, anhydrous 0.38 g
Sodium metabisulfite 2.96 g
Potassium Iodide 1.20 mg
Sodium Bromide 1.31 g
Hydroxylamine Sulfate 2.41 g
CD-4 4.52 g
Water to make 1 liter

Hmm, that formula is the same as (there was a url link here which no longer exists) of yours about half a year ago, except for rounding quantities. Yes, Big Brother is watching you.

Seriously, do you happen to have the patent-number for it? I saw your earlier posting a month ago, and assumed that you'd come up with that formula yourself. I'm curious who patented it, and what they had to say about it. A couple of Kodak patents I've encountered with plausible formulas in them are 6589721 and 6998227. Curiously, 6589721 has nothing in it to pull the pH down to its target of 8.1, unless DTPA happens to be very acidic.

Mark Overton

RPC · Apr 14, 2012

The formula I gave was not the subject of the patent but was included in the patent as an example. I do not know the original source of it. I modified it for simplicity it to be used with distilled water only and not tap water. Google this for more info: US5827635

The word is that the authentic Kodak C-41 Flexicolor formula is proprietary and not published. There are good and bad C-41 formulas published, so beware.

Photo Engineer · Apr 14, 2012

The formula in the patent and as posted by RPC is almost identical to the production C-41 developer formula.

Remember that the pH is critical and is 10.0 in the example.

PE

albada · Apr 14, 2012

Photo Engineer said:
The formula in the patent and as posted by RPC is almost identical to the production C-41 developer formula.
Remember that the pH is critical and is 10.0 in the example.
PE

RPC: Thanks for posting the patent-number. For the record, here's the one-litre formula from patent 5827635 referred to above. All units are grams:

Potassium Carbonate (Potash) ........ 34.3
Potassium Bicarbonate .................... 2.32
Sodium Sulfite .................................. 0.38
Sodium Metabisulfite ........................ 2.78
Sodium Bromide ............................... 1.3
Potassium Iodide (KI) ....................... 0.0012
Hydroxylamine Sulfate (HAS) ........... 2.41
CD-4 ................................................. 4.52
DTPA-Na5 ........................................ 3.37

Target pH is 10.0

There are small differences from RPC's formula, which he stated is a modification of the above formula.

The patent describes what happens if the HAS (an antioxidant) is omitted: After 24 hours at 57.5C, density drops 2.47%. This tells me that the HAS can be omitted if the CD-4 is mixed and used within a few hours.

I wonder if it would be feasible to split this developer into two long-lasting concentrates? One would be aqueous, and the other would contain CD-4 in an organic solvent such as propylene glycol. One would mix both and use them one shot. In fact, I suspect the resulting stock solution would last a few weeks if the HAS and DTPA were present in the aqueous concentrate. Any idea how long such an aqueous concentrate might last?

Mark Overton

Photo Engineer · Apr 14, 2012

THe HAS has side effects which the film (and the ingredients in that patent) are designed to compensate for. For example, HAS is a weak B&W developing agent that the film is designed around. So, beware of these side effects in your developer.

Then again, Kodak and Fuji are still using HAS, so that patent my work but may have side issues.

Also, if the kit could be made in 2 parts, don't you think Kodak would have done it? It will be difficult. For example, the CD-4 is a salt that may be difficult to dissolve in organic solvents, even PG.

PE

newcan1 · Apr 15, 2012

I do mix concentrates for C-41 but leave the CD4 dry. Concentrate 1 is everything but HAS; Concentrate 2 is HAS. When I mix them together and with water, I finally mix the CD4 with a little water on its own until dissolved, and then add to the mix. I find this works very well and is very convenient. The stocks seem to last very well, and the dry CD4 of course lasts a long time.

Photo Engineer · Apr 15, 2012

If you can get it, Diethyl Hydroxylamine Oxalate can be used instead of HAS and it comes as a premixed concentrate that can be used directly in the C-41 formula equal molar to HAS.

PE

Sirius Glass · Apr 15, 2012

Photo Engineer said:
The formula in the patent and as posted by RPC is almost identical to the production C-41 developer formula.

Remember that the pH is critical and is 10.0 in the example.

PE

Thank you for your input. Given the option of collecting all the reagents, weighing, measuring, and mixing versus purchasing the commercially available product, I will opt for the latter until the products are no longer available. I would rather both save my time and energy will supporting the remaining photo supplies.

albada · Apr 15, 2012

newcan1 said:
I do mix concentrates for C-41 but leave the CD4 dry. Concentrate 1 is everything but HAS; Concentrate 2 is HAS. When I mix them together and with water, I finally mix the CD4 with a little water on its own until dissolved, and then add to the mix. I find this works very well and is very convenient. The stocks seem to last very well, and the dry CD4 of course lasts a long time.

Why is HAS kept in a separate concentrate? Does it harm something else, or does something else (perhaps carbonate?) harm the HAS?

Mark Overton

newcan1 · Apr 16, 2012

I have no idea. I originally started with an old Zone V recipe and that's how they mixed the concentrates, and when I went with a slightly different formula, I just did the same. I'm not a chemist and feel greatly inferior to the intellect of those here who are.

Photo Engineer · Apr 16, 2012

Guys;

Wikipedia is your friend. Read here:

http://en.wikipedia.org/wiki/Hydroxylamine

DUH! and KABOOM.

PE

newcan1 · Apr 17, 2012

Shows how much of the world I fail to understand. PE, I read the Wikipedia article, and didn't understand a word of it, except I could see how KABOOM might be relevant!

Photo Engineer · Apr 17, 2012

Don't worry about it. The kit, when packed properly is ok.

PE

feromarcin · Jun 8, 2012

What function DTPA Na5 has in this developer? Is it necessary, to use it?

Athiril · Jun 8, 2012

Photo Engineer said:
DUH! and KABOOM.

This is actually one of my favourite past-times/hobbies.

Photo Engineer · Jun 8, 2012

DTPA is a sequestering agent as shown here: http://en.wikipedia.org/wiki/Pentetic_acid

PE

Mr Bill · Jun 8, 2012

albada said:
For that matter, does anyone have information on the C-42 process? My internet search turned up nothing.

Kodak's C-42 process was intended for large finishers where the conventional C-41 product lines perhaps did not make sense. For various reasons, Kodak was willing to license such finishers to bulk mix their own chemicals; the C-42 process was the version used. This was confidential information, and apparently the licensees did a good job keeping it so.

Mixing according to the "developer" formula was sort of irrelevant to C-42 licensees; no high-volume user would mix to this formula (aside from initial processor tank fills). Rather, they would mix to the "replenisher" formulation, and the seasoned processor tanks would tend toward the specs for "developer," generally called the "tank solution" by people in the business.

mohmad khatab · Jun 3, 2019

Mr Bill said:
Kodak's C-42 process was intended for large finishers where the conventional C-41 product lines perhaps did not make sense. For various reasons, Kodak was willing to license such finishers to bulk mix their own chemicals; the C-42 process was the version used. This was confidential information, and apparently the licensees did a good job keeping it so.

Mixing according to the "developer" formula was sort of irrelevant to C-42 licensees; no high-volume user would mix to this formula (aside from initial processor tank fills). Rather, they would mix to the "replenisher" formulation, and the seasoned processor tanks would tend toward the specs for "developer," generally called the "tank solution" by people in the business.

Hello, Gentlemen, God bless you all,
I am very embarrassed because of the many questions - I hope you do not get upset with me
If you allow me, I have some inquiries about this.
1 - Is this formula tested?
Have you proven successful and effective?
2 - PH - = 10 - Question: Will the figure differ if I use deionized water?
3. How much temperature should the installation process take?
4- What is the temperature of the process?
5-Is that process really considered C42 - or to what extent are they really close?
-6 The page here is two formulas, which is the final version of the experiment?
7- What about the modified C27 formula - did it really prove useless?
8. What is the optimal formula for the Bleach / Fixer solution - or Bleach separately and the Separate Fixer, which is the optimal formula, whether they are combined with one or two solutions.
9 - Also what is the optimal Stabilizer formula that does not depend on
Kodak's crystallization fluid, where photoflo or MX12 is not available in the Egyptian market, is there an acceptable alternative?
10 - Finally - how many rolls of film that can be developed a quantity of one liter of that formula.
I am very sorry for the prolongation, God bless you all.

Rudeofus · Jun 4, 2019

mohmad khatab said:
1 - Is this formula tested?
Have you proven successful and effective?

The C-42 formula has been published by Grant Haist, whom we can trust more than five people here including me singing high praises. Grant Haist was a researcher at Kodak and knew his stuff well.

mohmad khatab said:
2 - PH - = 10 - Question: Will the figure differ if I use deionized water?

C-41 CD is well buffered - unless you have crazy water supply, pH should work with tap water as well as deionized water

mohmad khatab said:
3. How much temperature should the installation process take?
4- What is the temperature of the process?

With "installation procedure" you mean the temperature for mixing the chems? Anything between 20°C and 50°C will work, the higher the faster the compounds will dissolve.

mohmad khatab said:
5-Is that process really considered C42 - or to what extent are they really close?

This formula is an approximation of C-41 CD but reformulated such that amateurs can easily source the ingredients. The real C-41 CD formula likely contains powerful sequestering agents which are hard to obtain. The sequestering agent used in C-42 formula (Kodak Anti-Calcium No. 3 = 1,3-Diamino-2-Propanol-N,N,N',N'-Tetraacetic Acid) is hard to get now, you can substitute it with equal molar amount of EDTA.

mohmad khatab said:
-6 The page here is two formulas, which is the final version of the experiment?
7- What about the modified C27 formula - did it really prove useless?

Since C-41 is a negative process and most people scan their negatives after processing, you can use just about any formula you can find out there, and you will get workable negatives. If you want accurate negatives, you will have to get C-41 control strips and do some testing and fine tuning yourself.

mohmad khatab said:
8. What is the optimal formula for the Bleach / Fixer solution - or Bleach separately and the Separate Fixer, which is the optimal formula, whether they are combined with one or two solutions.

The optimal formula is an Ammonium Ferric PDTA based bleach like the one published in US6649331 patent, and a powerful rapid fixer like Ryuji Suzuki's Neutral Rapid Fixer or Ron Mowrey's Superfix. Realistically it might be difficult to get Ammonium Ferric PDTA, so you could mix a bleach from Ammonium Ferric EDTA, Ammonium or Potassium Bromide and Mercaptotriazole. Target pH would be between 4.5 and 5.5, to be adjusted with Acetic Acid or Ammonia. Use fizzle test with Sodium Bicarbonate if you don't have a pH meter.

mohmad khatab said:
9 - Also what is the optimal Stabilizer formula that does not depend on
Kodak's crystallization fluid, where photoflo or MX12 is not available in the Egyptian market, is there an acceptable alternative?

You can try 30-50 ml pure Isopropanol plus 10-20 ml Formalin 20% in one liter of deionized water.

mohmad khatab said:
10 - Finally - how many rolls of film that can be developed a quantity of one liter of that formula.

Typical processing would run between 10-15 rolls through a liter of C-41 CD. There are people who got double or triple times that through a liter, but results at later iterations looked a bit "improvised". In a perfect world you'd use a rotary processor and use the C-41 CD single shot - this would give you about 8-10 rolls per liter.

mohmad khatab · Jun 5, 2019

Rudeofus said:
The C-42 formula has been published by Grant Haist, whom we can trust more than five people here including me singing high praises. Grant Haist was a researcher at Kodak and knew his stuff well.

C-41 CD is well buffered - unless you have crazy water supply, pH should work with tap water as well as deionized water

With "installation procedure" you mean the temperature for mixing the chems? Anything between 20°C and 50°C will work, the higher the faster the compounds will dissolve.

This formula is an approximation of C-41 CD but reformulated such that amateurs can easily source the ingredients. The real C-41 CD formula likely contains powerful sequestering agents which are hard to obtain. The sequestering agent used in C-42 formula (Kodak Anti-Calcium No. 3 = 1,3-Diamino-2-Propanol-N,N,N',N'-Tetraacetic Acid) is hard to get now, you can substitute it with equal molar amount of EDTA.

Since C-41 is a negative process and most people scan their negatives after processing, you can use just about any formula you can find out there, and you will get workable negatives. If you want accurate negatives, you will have to get C-41 control strips and do some testing and fine tuning yourself.

The optimal formula is an Ammonium Ferric PDTA based bleach like the one published in US6649331 patent, and a powerful rapid fixer like Ryuji Suzuki's Neutral Rapid Fixer or Ron Mowrey's Superfix. Realistically it might be difficult to get Ammonium Ferric PDTA, so you could mix a bleach from Ammonium Ferric EDTA, Ammonium or Potassium Bromide and Mercaptotriazole. Target pH would be between 4.5 and 5.5, to be adjusted with Acetic Acid or Ammonia. Use fizzle test with Sodium Bicarbonate if you don't have a pH meter.

You can try 30-50 ml pure Isopropanol plus 10-20 ml Formalin 20% in one liter of deionized water.

Typical processing would run between 10-15 rolls through a liter of C-41 CD. There are people who got double or triple times that through a liter, but results at later iterations looked a bit "improvised". In a perfect world you'd use a rotary processor and use the C-41 CD single shot - this would give you about 8-10 rolls per liter.

My dear I really thank you from the bottom of my heart, God bless you.
- I did not expect anyone to be interested in answering all these questions.
Allow me to offer you more thanks, gratitude and respect
Greetings to you.
But I am a bit confused about the following points:
1. The mixing temperature is 20 ° C (50 ° C)
2. What about the temperature of the process?
3 - Would you prefer to use Bleach / Fixer or would you prefer to have a Bleach bath separate from a fixer?
4 - What combination do you think is ideal for a single bath (Bleach) and a single bath (Fixer), and a Bleach / Fixer bath if you prefer the latter option.
God bless you
I do not know, I feel a lot of embarrassment because I'm really an annoying person and they seem foolish and somewhat ignorant,
- Could you, please, write me the whole recipe for the whole process in a neat manner, including the pH of each bath, the mixing temperature, the temperature of the operation, the time and the temperature of each bath?

God bless you and I really thank you again and I will keep thanking you for years to come,

RPC · Jun 5, 2019

Due to the complexity and design of color film, you must develop at 100F or 37.5C with a time of 3'15" for best quality. If you deviate from this you could see some color degradation, which may be acceptable to you, but be aware. The other solutions can be used at 75-105F or 24-42C.

A separate bleach and fixer has been shown to be better in image quality and film longevity than a combined bleach-fix and is what is recommended by film manufacturers and used by photofinishers.

Rudeofus · Jun 5, 2019

About bleach and fixer recipes: there are recipe for both published in US patent US6649331. Tables 3 and 4 give formulas for very powerful versions and are not exactly cheap, but at least the bleach processes a lot more rolls per liter than C-41 CD. If you want to create cheaper solutions with equal capacity, you could:

Mix any of the C-41 formulas. There really is not much wiggle room, these are all very similar in composition and capacity, which is 10-15 rolls per liter.
Mix bleach following the formula from US6649331 Table 3, but dilute it 1+2 or even 1+3 with water, then bring back to pH 4.2 - 4.5. Use the dilute bleach for 6-8 minutesl.
Follow Ryuji Suzuki's Neutral Rapid Fixer, ideal pH target for C-41 fixer would be 6.5. For some extra performance you can also use Ron Mowrey's Superfix. Use these fixers for 4-5 minutes. Although clearing time with both is much, much shorter, there are very insoluble silver salts created during C-41 development, and fixers take longer than twice clearing time to remove these.
Don't forget a final rinse! It's important to keep the film long term stable.

mohmad khatab · Jun 5, 2019

Rudeofus said:
About bleach and fixer recipes: there are recipe for both published in US patent US6649331. Tables 3 and 4 give formulas for very powerful versions and are not exactly cheap, but at least the bleach processes a lot more rolls per liter than C-41 CD. If you want to create cheaper solutions with equal capacity, you could:

Mix any of the C-41 formulas. There really is not much wiggle room, these are all very similar in composition and capacity, which is 10-15 rolls per liter.

Mix bleach following the formula from US6649331 Table 3, but dilute it 1+2 or even 1+3 with water, then bring back to pH 4.2 - 4.5. Use the dilute bleach for 6-8 minutesl.

Follow Ryuji Suzuki's Neutral Rapid Fixer, ideal pH target for C-41 fixer would be 6.5. For some extra performance you can also use Ron Mowrey's Superfix. Use these fixers for 4-5 minutes. Although clearing time with both is much, much shorter, there are very insoluble silver salts created during C-41 development, and fixers take longer than twice clearing time to remove these.

Don't forget a final rinse! It's important to keep the film long term stable.

Good evening to everyone
I find myself unable to write the words of thanks that are worthy of you, God bless you all.

I would like to thank the esteemed gentleman / Rudeofus
, And also thank the esteemed Mr. / RPC
- I am really very happy to help you, and I hope that I can return this gratitude to you, I hope to come to the pyramids where I live there and I will welcome you with all the kindness.
- In fact I find myself in need of requesting some scientific and technical support from a local chemist to help me explain and understand this large amount of scientific information and I am in fact just a (accountant)
God bless you all

C-42 is Kodak's home-version of C-41?

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