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  1. #11
    Ian Grant's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Formulas that originated through internal R&D were never published.
    PE
    Not strictly true when the developer was covered by a Patent, like Xtol, HC-110, but of course we can't be 100% sure the Patent version is identical to the final commercial product.

    Ian

  2. #12
    chriscrawfordphoto's Avatar
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    Kodak originated D76, didn't they? And it was published.
    Chris Crawford
    Fine Art Photography of Indiana and other places no one else photographs.

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    My Tested Developing Times with the films and developers I use

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    Fort Wayne, Indiana

  3. #13
    Ian Grant's Avatar
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    Quote Originally Posted by chriscrawfordphoto View Post
    Kodak originated D76, didn't they? And it was published.
    There were already fine grain MQ Borax developers, so D76 was a derivation balanced specifically for cine films.

    Ian

  4. #14
    Anscojohn's Avatar
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    Quote Originally Posted by Mahler_one View Post
    How about Zone vi developer? Is such also a variant of Dektol John?

    Ed
    *******
    I don't know. Except that any MQ paper developer is, essentially, D-72(Dektol), as far as I can tell.
    John, Mount Vernon, Virginia USA

  5. #15
    Anscojohn's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Dektol = D72 + a sequestering agent (at one time Calgon, then Quadrofos and now.... Dequest? IDK)

    The sequestering agent has nothing to do with the order of dissolution of ingredients, nor is it bonded to anything. It is just another part of the mix.

    The developing agents and the alkali are encapsulated in two different capsules of bonding agents which separate and protect the developing agents from the alkali. When they hit water, the "capsules" all dissolve and form a uniform mixture. The mix is packed under an inert gas.

    Neither the sequestering agent, nor the encapsulating material affect development properties unless you mix D72 using very hard water. In that case, you may get some sludge or a fine precipitate.

    If the formula for Zone VI = D72 then they are equal.

    PE
    ******
    I stand corrected.
    John, Mount Vernon, Virginia USA

  6. #16
    Photo Engineer's Avatar
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    Quote Originally Posted by Ian Grant View Post
    Not strictly true when the developer was covered by a Patent, like Xtol, HC-110, but of course we can't be 100% sure the Patent version is identical to the final commercial product.

    Ian
    That is exactly the problem.

    The Microdol-X formula is probably the most famous, but the HC-110 formula is almost impossible for the small experimenter to reproduce as it requires cylinders of Sulfur Dioxide gas and Hydrogen Bromide gas. Not nice things to store at home.

    And, the reactions involved to make it in-situ are messy and dangerous.

    I believe that the Xtol patent is also devious based on what Bill Troop and I have discussed regarding this patented formula. And, I know from experience that process chemistry is quite at variance with many patents which seem to disclose all.

    Interestingly, the patented formulas will (and of course must) work.

    PE

  7. #17

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    I thought I heard from you (PE), that Sylvia says the Xtol patent was a "teaching patent" - I took that to mean that the patent for XTOL pretty much disclosed the actual formula. Am I wrong in my interpretation of her comment?
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  8. #18
    Photo Engineer's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    I thought I heard from you (PE), that Sylvia says the Xtol patent was a "teaching patent" - I took that to mean that the patent for XTOL pretty much disclosed the actual formula. Am I wrong in my interpretation of her comment?
    All patents must "teach one skilled in the art, the method of operation of the claims of the patent". It does not state that the optimum formula must be disclosed and in fact, the claims give ranges and preferred ranges.

    Therefore, you, as a chemist, might make a very good educated guess and I might do even better due to experience, but an average person might be totally lost just by the very definition of the purpose of a patent.

    So, what I said to you was the quote above. I believe that Dick and Sylvia would agree.

    PE

  9. #19
    Ian Grant's Avatar
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    Quote Originally Posted by Anscojohn View Post
    *******
    I don't know. Except that any MQ paper developer is, essentially, D-72(Dektol), as far as I can tell.
    MQ paper developers can be very varied and differ in their use & effects but they tend to fall into groups.

    Normal, like D72 would be: Ilford ID-20, Dupont 53-D, Haloid D1, Agfa 125 plus many more

    Contrast Developers: Ilford ID-14, ID-21

    Warm Tone: Kodak D52 (Selectol), D32, D166, Agfa Ansco 135,

    There are so many variations for special uses that the list is enormous, but the ratios of Metol to Hydroquinone, the Sulphite & Carbonate levels as well as the Bromide are all varied to give different contrasts and image colour, ranging from Blue Black to very warm Red-brown tones and High Contrast to softer working although the softest working developer like Selectol Soft (D165) and ID-3, Adaptol etc are Metol only.

    Ian

  10. #20
    tony lockerbie's Avatar
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    Wow, thanks for that...the usual wealth of information!

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