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  1. #1
    Ian Grant's Avatar
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    Modern Rodinal Substitutes Part II

    Apologies for having to start a new thread but I can't read or even access the first to reply to posts.

    So with a bit of telepathy

    Quote Originally Posted by Kirk Keyes View Post
    Well, there's a problem there, as it's really hard to measure pH accurately when it gets much above 12.5 or so. You have to start getting special electrodes and the like.

    But for MSDS work, it doesn't have to be too precise.
    __________________
    Kirk

    A point that's being missed is that A&O give a figure of 2.7% Potassium Hydroxide not 3% in older Agfa MSDS.

    The pH is around 14 sure, but the actual requirement is the pH of the working dilute solution rather than the concentrate which is given elsewhere as pH 11.55, which I commented on in the first post of the thread.

    Way back Ron (PE) mentioned adjustments to Rodinal before bottling, the question we need to ask is are they adjusting on the basis of the concentrate, or also doing some tests on a dilute sample, as this will be a far more accurate indicator.

    Can someone please post a link to this continuation on the original post.

    Ian

  2. #151
    Photo Engineer's Avatar
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    Patrick;

    I would not think that it would be very stable. I have not seen it for sale recently, but that may have changed.

    The Metol equivalent of Rodinal that you were working on is very similar, if not identical to Kodak HDD, a developer sold many years ago and described in Anchell and Troop. It was quite stable.

    However, plain Metol in Sulfite and Hydroxide is not. Among other things, it can form Sulfate precipitates which is why I assume you are trying to get the free base of Metol. This would solve the occasional precipitate problem and the relative concentration problems, but not the stability problem. This needs additional ingredients as you have probably already found.

    PE

  3. #152
    Ian Grant's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Patrick;

    The Metol equivalent of Rodinal that you were working on is very similar, if not identical to Kodak HDD, a developer sold many years ago. It was quite stable.

    PE
    Kodak HDD wasn't stable, like Ilford's Hyfin, and Neofin Blue etc it had to be made up just before use, the very low sulphite level of these developers means they need to be used within an hour of mixing.

    So the opposite of Patrick's formula

    Crawley noted that Kodak HDD really worked best with Panatomic-X and wasn't really suitable for all films, Tetenal recommended their Windisch formulated HDD for Adox films, and Hyfin was particulary suited to Pan-F and FP3.

    Ian
    Last edited by Ian Grant; 09-06-2009 at 01:48 PM. Click to view previous post history. Reason: add

  4. #153
    Photo Engineer's Avatar
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    Ian;

    A&T state that the stability may have been one of the reasons Kodak HDD was discontinued. I know that. And, that is my point.

    A Metol version of Rodinal is potentially doomed to failure through instability regardless of sulfite level. IDK for sure, but it points that way. Metol is much more reactive than pAP as a reducing agent, and if it outstrips sulfite as a reducing agent, then sulfite will not preserve it very well at all.

    Kodak HDD is not the "opposite" of Patrick's formula, it is an analog of his formula.

    The Kodak HDD design was optimized for older film emulsions as stated by James. It was dropped when emulsions were redesigned rather than continue to produce a marginal product and redesign of the developer was probably considered to be uneconomical. Rodinal was probably redesigned at that time due to the same changes. IDK, but I have mentioned before that changing emulsion types would probably require updated developer formulas.

    Not knowing the details, many authors might ascribe things the way Crawley did regarding optimum developer/film combinations. Only insiders might know when an emulsion change would change the response of a product to a given developer.

    PE

  5. #154

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    Metol is said to be sensitive to hydrolysis in alkaline media:
    http://books.google.co.uk/books?q=me...G=Search+Books

  6. #155
    Ian Grant's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Ian;
    Kodak HDD is not the "opposite" of Patrick's formula, it is an analog of his formula.
    PE
    Opposite in terms of the amount of sulphite levels, high versus minimal. We're use the word analogous quite differently, of course we're talking about developers using the same components..

    In practice those High Definition Developers will still work well with some modern emulsions, the PF sells Crawley's version and European manufacturers make their own equivalents. They've always been a very European thing, it's like Kodinol the Kodak HDD was not available in North America.

    Crawley's BJP article Jan 6th 1961 is quite interesting, and he did a lot of work on High Acutance developers. Hee mentions the stability problems.

    I'd guess a major reason Ilford & Kodak dropped their HDD's was low sales,the Tetenal Neofin products were better known and sold well. I have some Hyfin but it wasn't stocked by many retailers.

    Ian

  7. #156
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    Quote Originally Posted by Alan Johnson View Post
    Metol is said to be sensitive to hydrolysis in alkaline media:
    http://books.google.co.uk/books?q=me...G=Search+Books
    That is not immediately obvious looking at the structure, and the odor on decomposition indicates some rather exotic chemistry.

    If it were that sensitive, Metol developers would be quite impossible to compound and so the reaction would have to be rather slow at normal pH values. IDK yet. I'm still examining the situation.

    PE

  8. #157
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    I seem to remember seeing an acorbate form of Metol, using, I guess. ascorbic acid in place of sulfuric acid on its tail. I am thinking of adding just enough alkali to precipitate the base, then if I'm lucky I will be able to dissolve it again with ascorbic acid after decanting most of the sulfate. Why I would attempt such a thing, IDK. Too much time on my hands, I guess.
    Gadget Gainer

  9. #158

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    As things have settled down, it would be nice to see parts 1 and 2 of Modern Rodinal Substitutes merged.

  10. #159

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    Quote Originally Posted by Photo Engineer View Post
    That is not immediately obvious looking at the structure, and the odor on decomposition indicates some rather exotic chemistry.
    I hear is smells like the breath of death! ;^)

    That probably would NOT be a big selling point.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  11. #160

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    By the way - I once was looking through a "hard to find" standards catalog, and they were offereing "psuedo-corpse scent". It came in 4 versions, on ground and underwater versions - and each of them came in 2 day old and 7 day old...

    Here's some: http://www.sigmaaldrich.com/analytic...lePage=9620039
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!



 

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