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  1. #11

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    From "Amateur Photographer" Sept 25 1946:
    "The sustance known as Meritol consists of a compound or mixture in equimolar parts of para-phenylenediamine and pyrocatechin.
    The preparation is carried out as follows according to Patent Specification No.466,626 of Jun 1st, 1937:-
    100 lb para-phenylenediamine is dissolved in 80 gallons of a 10 per cent solution of sodium bisulphite with the aid of heat, 2 lb decolourising carbon added, the mixture well stirred for 10 minutes and filtered hot; to this a hot solution of 100 lb of pyrocatechin in 20 gallons of a 10 percent solution of potassium metabisulphite is added; on cooling the new compound separates out in beautiful colourless prismatic crystals which melt at 110 degrees C and are remarkably stable in the air.
    Similarly by substituting an equivalent quantity of pyrogallol or chlorquinol for the pyrocatechin in the above example the corresponding compounds are readily obtained."

    I mention this out of interest only,NB some of these substances are highly toxic, don't try this at home!

  2. #12

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    "ein langsamer Entwickler für Warmtonpapiere"! http://www.moersch-photochemie.de/co...ie/se30meritol
    -
    Philippe Grunchec

    "The fundamental problem any artist faces in regard to craft is that it must be largely ignored" Richard Benson.

    http://philippe.grunchec-photographe.over-blog.com/

  3. #13

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    Meritol was the tradename for the addition product of p-phenylenediamine and catechol. Once dissolved it dissociated into its two components. Nothing magical and not really a useful developing agent with today's emulsions.
    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

  4. #14
    Ian Grant's Avatar
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    I think your maybe wrong Jerry. I use Meritol based developer as a teenager and i think that a PPD-Pyrocatechin developer like Pyrocat would have great potential. I don't think I'd use 50/50 ny MW though, much less PPD so strictly it would be Meritol-Pyrocatechin.

    Ian

  5. #15

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    Hi Ian,

    Such developing agents as Meritol were a response to the thick emulsions of the time. They did provide finer grain but at the expense of sharpness and speed. Many years ago I got caught up with the search for the "holy grail" of developers. I tried several PPD developers and also solvent types such as Microdol. All yielded finer grain but with mushy images. With today's finer grain films, I see no advantage in their use. Of all the developing agents ascorbic acid seems to be closest to the ideal. Ascorbic acid produces much less infectious development than any other developing agent thereby yielding greater sharpness.
    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. #16
    Ian Grant's Avatar
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    Unfortunately Johnson's later proprietary developer formulae have never been published. The company was poorly managed and they dropped their raw photochemical manufacturing side and then their chemistry. Their chief chemist Pip Pippard set up Photo Technology with others but they mainly specialised in Colour chemistry and made a only a small B&W range.

    Johnson's had fine grain developers with excellent definition, but the key isn't Meritol, it's PPD for the fine grain and Pyrocatechin for the definition.

    You could reformulate Pyrocat HD with PPD instead of Phenidone, it'd be slower but probably finer grained. I think the mistake is to think that Johnson's Meritol is a "New" developing agent, which is what they claimed. Edmund Lowe thought differently

    Ian

  7. #17
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    Quote Originally Posted by piticu View Post
    Do you mind digging the book out and check the page no that formula is on? Or scan the page if it's not too much to ask?
    I need that info for a small project i'm working on. http://bwformula.atelierelealbe.eu/index.php/JJ97
    Thanks
    Of course I can do that, if you still are interested. Sorry about the late reply but life (relationship breakup, new home, no darkroom, etc, etc) has come between me and APUG for the last 7-8 months.
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  8. #18
    Jerevan's Avatar
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    Let's see if the uploaded picture is enough to read the text from the book - it's not much, just the recipe and that's it.
    Attached Thumbnails Attached Thumbnails Meritol.jpg  
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  9. #19
    K-G
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    Quote Originally Posted by Jerevan View Post
    Let's see if the uploaded picture is enough to read the text from the book - it's not much, just the recipe and that's it.
    Good to see you back again.

    Karl-Gustaf
    Karl-Gustaf Hellqvist

    www.heliochroma.com

  10. #20
    Jerevan's Avatar
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    Thanks Karl-Gustaf!

    Well, I guess things are coming along in the right direction again. The analogue, darkroom direction that is.
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

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