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Thread: Acid Developers

  1. #11
    Ian Grant's Avatar
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    Phritz, I've not tried looking for it yet. I'm not sure how you access German Patents online, British Patents aren't as easy to access as US or the new EP patents.

    Also there are Acid Amidol formulae already in my L.P. Clerc book in the UK. The Patent dev needs to be acidic to destroy a particular sensitising dye during processing, it's a Red dye and has to be destroyed before development can be complted.

    Ian
    Last edited by Ian Grant; 07-31-2009 at 10:52 AM. Click to view previous post history.

  2. #12
    Thomas Bertilsson's Avatar
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    I tried Weston's Amidol with Fotokemika Emaks paper a while back. I probably made my best portrait prints ever with that combination, but I have abandoned amidol for the benefit of a different developer that I like better.
    But I think that formula is acidic.

    - Thomas
    "Often moments come looking for us". - Robert Frank

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    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  3. #13

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    L P Clerc's Monochrome Processing revised by R.E.Jacobson section 559 explains how depth development works.G.Balagny (1903) used amidol and sulfite and added bisulfite.As this diffuses through the gelatin,because of its amphoteric character the gelatin reacts with some of the bisulfite ions reducing the acidity of the solution to allow it to develop in the depth of the layer.Development spreads slowly towards the free surface of the emulsion without reaching it.

  4. #14
    Ian Grant's Avatar
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    The earlier copies of Clerc are even more interesting, if Professor R.E. Jacobson was born he'd have been extremely young, I think my copy is translated then edited by Bottomley the then editor of the BJP It's too heavy to fly with

    Ian

  5. #15
    gainer's Avatar
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    In general, ferrous sulphate in a solution with excess potassium oxalate, kept slightly acidic, was important both practically and theoretically according to Mees & James. This was compared with Pyro-sodium carbonate by Hurter & Driffield. They preferred the Pyro-Soda.
    Gadget Gainer

  6. #16

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    More Clerc:
    The theory that the gelatin reacts with bisulfite was proved by covering the gelatin with another sheet of gelatin,when the developer diffusing through this develops the image on the surface of the emulsion,L.P. Clerc and G.E.Brown, Photography, Edition 2 1946 p244.

  7. #17
    Ian Grant's Avatar
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    Got the name wrong Brown not Bottomley, I'm reading too many old BJP Almanacs, I think I have a 1941 reprint of the first edition. It's a very interesting and comprehensive book, do you have D.A. Spencer's Colour Photography, which is the same publishers and a contemporary book at that time ?

    Ian

  8. #18

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    No Ian I don't have Spencer's book.Maybe you can tell us what was hot in color developers in the 1940's another time!

  9. #19

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    Quote Originally Posted by Ian Grant View Post
    Phritz, I've not tried looking for it yet. I'm not sure how you access German Patents online, British Patents aren't as easy to access as US or the new EP patents.
    Ian
    i did a quick search and found this:

    patent (pdf)

    this is the patent i found under the number "de 29937". it contains no information about photographic chemistry, it's about a mechanism for emptying equipment for galvanization processes.

  10. #20
    Ian Grant's Avatar
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    Quote Originally Posted by Alan Johnson View Post
    No Ian I don't have Spencer's book.Maybe you can tell us what was hot in color developers in the 1940's another time!
    Unlike Clerc Spencer's book has less of modern practical use, but it's a very interesting insight into older and lost processes, well written with extremely apt quotations from "Alice through the Looking Glass".

    Ian

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