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  1. #1

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    Kodalk substitute

    Hello

    In my country Kodalk (sodium metaborate) isn't available for purchase. I know what kodalk can be replaced with borax+NaOH and sometime I used this. But now I want find other solution for buffer with same pH, because I don't like working with NaOH.
    I found that carbonate-bicarbonate isn't good for kodalk replacement because optimal pH range for this system is 9.5..10.5.
    Other possible substitution is DEA with pH in range 10.5..11.5. Maybe mixture of TEA+DEA will be good buffer in range 10..11.
    In Anchell "Darkroom Cookbook" I found next recomendation for substitute kodalk:
    Yet another substitution is to use 4 parts sodium carbonate, monohydrate, and 1 part borax to equal the same weight of Balanced Alkali (e.g., 10.0 grams of Balanced Alkali equals 8.0 grams of carbonate and 2.0 grams of borax).
    I haven't found any details in google about carbonate-borax buffer, just only that such type of buffer used for pH in range 10-11. Someone try this?

  2. #2

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    From a Kodak formulary, 2 grams of "KODALK" (sodium metaborate) can be substituted with 0.3 gram of sodium hydroxide (caustic soda) and 1.4 grams of Borax (decahydrate).

  3. #3

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    In which formula would you want to replace Kodalk?
    Last edited by Gerald C Koch; 07-19-2012 at 07:13 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.

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  4. #4

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    not in 2bath. DK-76, DK-50 and other

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    Substituting one chemical for another in a developer is an "iffy" situation. I would say to try Anchell's suggestion but to test it first. If the negatives are too contrasty then reduce the ratio of carbonate to borate.
    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

  6. #6

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    ohh ... yes, I can mix carbonate+borax in different proportion and measure pH of solution but open question - what is the target pH of DK-50?

  7. #7
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    The correct substitution is as Keith says 10gm Sodium Metaborate (Kodalk) is equivalent to 7gm Borax and 1.5g Sodium Hydroxide, and this substitution has been in use for well over 50 years.

    Kodak have published this substitution themselves in Professional Handbooks and it's reliable. Kodalk hasn't been available in the UK for many years.

    Ian
    Last edited by Ian Grant; 07-20-2012 at 05:12 AM. Click to view previous post history.

  8. #8

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    Quote Originally Posted by Relayer View Post
    ohh ... yes, I can mix carbonate+borax in different proportion and measure pH of solution but open question - what is the target pH of DK-50?
    There is an MSDS here, which says pH = 9.5 for a working solution: http://www.chemcas.com/msds112/cas/4...-9_55-55-1.asp

    I don't know how reliable this number is, though.

  9. #9
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    You could possibly get sodium metaborate from Photographer's Formulary in the US. They ship it to Canada; I imagine they can ship it anywhere.

    It lasts a long time so if you buy a good amount you will have a supply that will last you for many years, possibly justifying the shipping expense.
    Jim MacKenzie - Regina, Saskatchewan, Canada

    A bunch of Nikons; Feds, Zorkis and a Kiev; Pentax 67-II (inherited from my deceased father-in-law); Bronica SQ-A; and a nice Shen Hao 4x5 field camera with 3 decent lenses that needs to be taken outside more. Oh, and as of mid-2012, one of those bodies we don't talk about here.

    Favourite film: do I need to pick only one?

  10. #10

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    Having practiced photography for over 60 years I have never seen a pH value given for DK-50. This is why I suggested running a few test negatives and adjusting the ratio of carbonate to borate on the basis of the tests. If the negatives are too contrasty then reduce the ratio (less carbonate). If they lack contrast then increase the ratio.
    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

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