Pyro Paper Development

Discussion in 'B&W: Film, Paper, Chemistry' started by Mustafa Umut Sarac, Jul 4, 2013.

  1. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    I am reading on pyro with large time intervals. If I am not wrong , pyro effects emulsion with harder or softer zones. And harder the zones , it is more squeezed and lower profil.
    And I am thinking carbon printing. Do pyro development of papers reveals a carbon like higher lower profile map ?

    Thank you,

    Mustafa Umut Sarac
    Istanbul
     
  2. jeffreyg

    jeffreyg Subscriber

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    I can't answer your question but I use PMK Pyro for film and know it is quite toxic so I would hesitate to use it for paper since paper requires more handling and would be in a tray as opposed to a tank which would be closed or more confined (using film holders) for large format.

    http://www.jeffreyglasser.com/
     
  3. Ian Grant

    Ian Grant Subscriber

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    I do use a Pyrocatechin tanning developer for prints, there's no relief effect, the emulsions are already well pre-hardened so you don't get the same swell effects.

    Also you probably need need a paper with no supercoat. Etch bleach works though, it's best with RC papers.

    Ian
     
  4. Kobin

    Kobin Member

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  5. Gerald C Koch

    Gerald C Koch Member

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    As a chemist I tell people to avoid pyrogallol due to its toxicity. This is a dangerous chemical and urge people to read the MSDS for it. The LDlo (lowest lethal dose) is only 28 mg per kilo of body weight which is much lower than other developing agents. it is rapidly absorbed through the skin and so protection like nitrile gloves are a must. In addition it is expensive and oxidizes rapidly in solution.
     
  6. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    Gerald,

    Thank you for your warning. What do you say about Pyrocatechin ?

    Thank you,
    Umut
     
  7. Gerald C Koch

    Gerald C Koch Member

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    Catechol (the preferred chemical name) has about a third the toxicity of pyrogallol. Still it is considerably more dangerous than hydroquinone. This may be because the human body uses a group of chemicals known as catecholamines and catechol may interfere with their use. Catechol has a measureable vapor pressure at room temperature and the solid should be used with adequate ventilation. It has a distinctive phenolic odor reminiscent of the smell of an old-time drugstore.