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  1. #1

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

    Grant Haist is still alive, and he is selling new copies of his two-volume set, Modern Photographic Processing. Go to http://www.haistpress.com/index.html 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 here.

    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: http://www.apug.org/forums/forum40/4...developer.html

    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

  2. #2
    RPC
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    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.

  3. #3

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    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.

    Quote Originally Posted by RPC View Post
    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 this posting 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

  4. #4
    RPC
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    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.

  5. #5
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    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

  6. #6

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    Quote Originally Posted by Photo Engineer View Post
    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

  7. #7
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    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

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    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.

  9. #9
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    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

  10. #10
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    Quote Originally Posted by Photo Engineer View Post
    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.
    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

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