Dk-76.

Discussion in 'Darkroom Developing and Printing' started by Keith Tapscott., Jul 17, 2008.

  1. I saw a formula for a developer called DK-76 which is the basi
    D-76/ID-11 formula, except that the Borax is replaced with an equa
    weight of Sodium Metaborate. Is this an official `Kodak` formula?

    http://www.digitaltruth.com/techdata/dk76.ph
     
    Keith Tapscott., Jul 17, 2008
    #1
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  2. Yes. At one time it was believed to give better shadow detail. I do not know
    if that was true or not.

    D-76d is yet another similar formula, but its buffering is better. Its main
    advantage is that it does not gain strength with exposure to air (as in a
    partly filled bottle). It is the same as D-76, but instead of 2 gm/l of
    borax, it uses 8 gm/l of borax and 8 gm/l of boric acid. Many believe that
    is what you get if you buy commercial D-76.
     
    Jean-David Beyer, Jul 17, 2008
    #2
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  3. "Keith Tapscott." <>
    wrote in message
    It is although it was first published as Kodalk D-76
    without the DK prefix. At the time it was thought that the
    metaboate would be able to buffer the pH of the developer
    but it was not effective so the buffered version D-76d,
    announced in 1929 remains the preferred version. DK-76 was
    formulated at the time Kodalk was made available by Kodak
    who published several developer and fixer formulas using it
    at the time. Kodak did not invent metaborate but did patent
    an economical method of producing it.
    The buffering is made necessary by a slow increase in pH
    in the original D-76 which affects its activity enough to
    cause problems in predicting results. This effect is caused
    by a slow reaction between the hydroquinone and the sodium
    sulfite which results in a small amount of sodium hydroxide.
    This effect was discovered shortly after the D-76 formula
    was first published (1927) and a research project at Kodak
    Labs resulted in the buffered version D-76. The researchers
    did not discover the cause of the pH increase, only that it
    did increase. The discovery of the hydroquinone/sulfite
    reaction was not made until the 1950s. For reference here
    are the two formulas:

    D-76 (original)
    Water (at 125F) 750.0 ml
    Metol 2.0 grams
    Sodium sulfite, desiccated 100.0 grams
    Hydroquinone 5.0 grams
    Borax, granulated 2.0 grams
    Water to make 1.0 liter

    The buffered version is:
    D76d
    Water (at 125F) 750.0 ml
    Metol 2.0 grams
    Sodium sulfite, desiccated 100.0 grams
    Hydroquinone 5.0 grams
    Borax, granulated 8.0 grams
    Boric acid, crystaline 8.0 grams
    Water to make 1.0 liter

    The above has the same activity as the original formula when
    its freshly mixed and retains that activity in storage. The
    activity can be varied over a wide range by changing the
    ratio of borax to boric acid.

    The Kodalk version is the same as the original version but
    uses 2.0 grams of Kodalk (sodium metaborate, octahydrate) in
    place of the borax.

    Current packaged D-76 is the buffered version.

    Virtually every film maker has published some version of
    D-76, they are all pretty similar in practical results.
    Kodak seems to have been the only one to recognize the
    necessity for buffering.
     
    Richard Knoppow, Jul 17, 2008
    #3
  4. Thanks Jean-David and Richard for replying. I had not seen the DK-7
    formula in any of my own Kodak publications and wasn`t sure if it was
    genuine Kodak formula, thanks for clarifying.
    I suspect that both Ilford as well as Kodak may well have made som
    subtle modifications to the basic formula over the years, I als
    suspect that the current Ilford ID-11R replenisher is close to th
    "modified" replenisher on page 17 of Kodak publication `03`. I hav
    seen some excellent prints from a former commercial photographer wh
    uses replenished ID-11 for processing B&W sheet-films. See page 7 o
    the ID-11 technical information "Replenishment"..
    http://www.ilfordphoto.com/Webfiles/20062161159472874.pdf
     
    Keith Tapscott., Jul 17, 2008
    #4
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