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  1. #1
    Lukas_87's Avatar
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    Crawley FX-37 sharpness modification?

    Hello,
    the FX-37's formula is known:

    Sodium sulfite - 60.0 g (I used 70 g, from other source)
    Hydroquinone - 5.0 g
    Sodium carbonate - 5.0 g
    Phenidone - 0.5 g
    Borax - 2.5 g
    Potassium bromide - 1.0 g (substitute for Kbr + benzotriazole)

    I like this developer on both tabular_grain and old_type emulsions for it's nice compensating tonality and sharpness. But sometimes I don't need so much sharpness so I'm thinking of altering the recipe to "smoot the things" a bit, just like Instant Mytol does (but I dislike it's tonality a bit).

    I suppose that bromide is used only as a restrainer and don't affect grain size/structure.
    Sodium carbonate with Borax makes a "strong" pH buffer? Does anyone know FX-37's target pH (theoretical or measured)?
    Also someone said that in sodium carbonate buffered developer the grain size isn't that much affected by amount of sulfite, so using higher amount of sulfite seems to be undesirable and lowering the amount of carbonate sould make enough change in developer's pH to allow more sulfite soving action? Also the development times will rise, right?

    Or I'm absolutely wrong and stupid? :)
    Can please local mages of BW developers help me a little bit?
    Thanks in advance.

    ---
    and please excuse my bad english, im still learning

  2. #2
    RobertV's Avatar
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    Dobry Den ,

    Just from the web:
    Geoffrey Crawley wrote (Amateur Photographer 17 Feb 07) to the effect that the sharpness of FX-37 is the result of the combination of borax and carbonate as alkalis.

    Further you have an extra 10g Sodium Sulfite which reduces the film grain but generate less sharpness according my own experiences.
    Also by a more dilution (less concentrate Sodium Sulfite) you will have sharper negatives.

    For the rest I hope some more experienced chemists can chime in to give you more information about the FX-37 developer.

    Robert

    PS. I do not think your English is any problem at all.

  3. #3

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    Geoffrey Crawley wrote (Amateur Photographer 17 Feb 07):
    "The sharpness of FX-37 is a result of the combination of borax and carbonate as alkalis.The carbonate just beefs up the natural softness given by borax without a noticeable increase in grain.That is assisted by the milder solvent effect of the reduced sulphite content compared to a D-76 type developer"
    By my measurement the pH of FX-37 1+3 is just under 10.
    Although I have never seen a complete account of how the pH increase due to carbonate affects the sharpness of PQ developer,I think that is what Crawley was getting at and my guess would be that you are correct to suggest reducing the carbonate would reduce sharpness and increase development time.

  4. #4

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    I mixed some Fx-39 with Xtol and got something in the middle. If FX-37 is about the same as FX-39 I agree that something a touch softer would be ideal. Thats what I was looking for!

    When back in civilisation I might again try with the FX-37/9 dev and try to soften it a touch. That would be about perfect for me for almost everything. I even found Neopan 400 could be pretty good looking in FX-39...



 

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