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  1. #1

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    Phenidone-ascorbate developers at low pH~7

    Hello

    I once read that developing film in Diafine bath A for 40-50 minutes produce some thin image. This is very interesting, because this bath contains P+Q in acid solution. So for testing I was replcae Q with C and mix next:

    RD-107 developer
    Sodium sulfite 30g
    Phenidone 0.2g
    Sodium ascorbate 4g
    Sodium metabisulfite 5g
    Water 1l
    pH 7.2

    for Neopan SS 100 (expired) I found next development time: EI 100 - 20min, EI 200 - 30min, EI 400 - 50min. all done at 23C and WITHOUT AGITATION! just first 1min initial agitation and leave stand for rest time.
    Negatives obtained is very clear and fine grain

    PS if you ommit phenidone from formula - you will have blank film. so phenidone is important part

  2. #2

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    Looks interesting. Could it be made up as a concentrate to be diluted 1+3? At this pH it should keep quite well in a sealed bottle.

  3. #3

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    Quote Originally Posted by Alan Johnson View Post
    Looks interesting. Could it be made up as a concentrate to be diluted 1+3? At this pH it should keep quite well in a sealed bottle.
    concentrate isn't need because developer can be reused.
    at low pH solution have long keeping time. in my experiment I was initially try Diafine-C bath A 1 year old - its work!

  4. #4

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    Since the first bath of a two bath developer is meant to be saved and used again you really need to include an appropriate chelating agent. No doing this may result in an Xtol style sudden death. The need for a chelating agent with ascorbate developers has been extensively discussed on APUG.
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    Quote Originally Posted by Gerald C Koch View Post
    The need for a chelating agent with ascorbate developers has been extensively discussed on APUG.
    Salicylic acid + TEA ?

  6. #6

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    Relayer - is the ascorbate active at all at that pH?

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    Quote Originally Posted by Relayer View Post
    Salicylic acid + TEA ?
    Better than using nothing. However, people who use two bath developers keep the first bath for so long that a more powerful chelating agent might be needed. The problem is that such agents are not readily available to the public. More than anything else this problem limits the usefulness of an ascorbate based two bath developer.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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  8. #8
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    Quote Originally Posted by Gerald C Koch View Post
    ... chelating agent might be needed. The problem is that such agents are not readily available to the public ...
    Would EDTA or Hexametaphosphate (old-style Calgon) work, or do you think a mercaptan is needed?
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  9. #9

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    Quote Originally Posted by Nicholas Lindan View Post
    Would EDTA or Hexametaphosphate (old-style Calgon) work, or do you think a mercaptan is needed?
    EDTA and sodium hexametaphosphate both accelerate the degradation of ascorbate. The choice of a suitable chelating agent is limited. A mercaptan can cause fogging and they are poor chelating agents. There is little data available as to which chelating agents are useful and which are not.

    What may not be understood is that the oxidation of ascorbate is a kinetic reaction. The choice of chelating agent is one the factors that determines the speed of the reaction. The reaction can be slowed but it is never completely stopped.
    Last edited by Gerald C Koch; 06-15-2012 at 04:04 PM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  10. #10
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    Quote Originally Posted by Gerald C Koch View Post
    There is little data available as to which chelating agents are useful and which are not.
    PhotoEngineer has recommended Dequest 2010, which is an extremely potent iron sequestrant. When you use it, be aware that it is very acidic. Since the TO lives in Europe: Fototechnik Suvatlar sells it under the name Fotoplex 2.
    Trying to be the best of whatever I am, even if what I am is no good.

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