Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 68,659   Posts: 1,481,500   Online: 1123
      
Page 3 of 3 FirstFirst 123
Results 21 to 26 of 26
  1. #21
    Ian Grant's Avatar
    Join Date
    Aug 2004
    Location
    West Midlands, UK, and Turkey
    Shooter
    Multi Format
    Posts
    15,936
    Images
    148
    Quote Originally Posted by Gerald C Koch View Post
    Kodak D-25 developer was developed as a safer substitute for ppd developers. It is D-23 with the addition of 15.0 g/l of sodium bisulfite. It is said to produce fine grain comparable to that of the phenylenediamine developers with less chance of causing allergic dermatitis.
    D-23 and D-25 were published at the same time, in fact Kodatol was Kodak's alternative to PDD super fine grain developers, they were all part of the same research project which included an early version of Microdol. Kodak chose to sell Kodatol DK-20 and then switched to Microdol and finally Microdol-X. There were issues with dichroic fog with Kodak films and D-25 and DK-20 and later Microdol. This got worse when Kodak improved their films in the 60's.

    Ian

  2. #22
    eclarke's Avatar
    Join Date
    Jun 2004
    Location
    New Berlin, Wi
    Shooter
    ULarge Format
    Posts
    1,913
    Images
    71
    Quote Originally Posted by Gerald C Koch View Post
    There was a contributor to the BJ by the name Cyril Peckham. His formulas were rather curious in that he mixed metric units with English units (grains, scruples, etc) in the same formula. He would use whatever measure gave him a round number. His Amidol paper developer was said to be quite good.
    Thanks, Gerald, I'll have to check him out, I have a collection of the BJ..

  3. #23

    Join Date
    Jun 2009
    Location
    Odessa, UA
    Shooter
    35mm
    Posts
    234
    from patent US3917695:
    The solubility of p-aminophenol in water can be increased by addition of inorganic acids such as sulfuric or hydrochloric
    from other patents related to PAP purification you can find information about participation PAP from acidic solution. many patent state that participate PAP doing at pH > 6

  4. #24

    Join Date
    Sep 2006
    Shooter
    35mm
    Posts
    769
    Are you using 11X14 film or something smaller and then enlarging to 11X14? If you are using 11X14 film and grain is a worry you must be making very large prints. If you are using a small format like 35mm then just go up to 6X7 and you can make grainless 11X14s with any number of develoopers.

  5. #25
    eclarke's Avatar
    Join Date
    Jun 2004
    Location
    New Berlin, Wi
    Shooter
    ULarge Format
    Posts
    1,913
    Images
    71
    Quote Originally Posted by dynachrome View Post
    Are you using 11X14 film or something smaller and then enlarging to 11X14? If you are using 11X14 film and grain is a worry you must be making very large prints. If you are using a small format like 35mm then just go up to 6X7 and you can make grainless 11X14s with any number of develoopers.
    Not worried about grain, just interested in photochemistry. I photograph with formats up to 11x14 and have all the methods in place for my serious photography. I like to dabble with developers for fun and sometimes while dabbling, I bring a new tool into my arsenal. I'll make this and when it comes up in conversation, I'll know all about it!! My original question was about the tiny amount of sulfuric acid at the exact place its added to the mix, a little odd compared to most recipes..Thanks, Evan Clarke

  6. #26

    Join Date
    Feb 2010
    Location
    Montreal, Canada
    Shooter
    Multi Format
    Posts
    4,250
    Evan - when you have some results please post back. Always curious to hear impressions.

Page 3 of 3 FirstFirst 123


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin