EDTA bleach for b&w?

Discussion in 'B&W: Film, Paper, Chemistry' started by Domin, Jan 28, 2008.

  1. Domin

    Domin Member

    Messages:
    204
    Joined:
    Oct 11, 2006
    Location:
    Warszawa, Po
    Shooter:
    Med. Format RF
    I recetly bought some c41 bleach replenisher rather cheap. Looking from the replenishment rates its enough to process ~1500 rolls of 135 film which is probably more than I need in my whole life.

    Is EDTA bleach ok for b&w paper and film? I suppose that it works but I suspect some caveats.
     
  2. Mike Wilde

    Mike Wilde Member

    Messages:
    2,936
    Joined:
    Aug 10, 2006
    Location:
    Misissauaga
    Shooter:
    Multi Format
    not a chemist, but..

    the EDTA in the bleach replensiher I would guess is added in along the way to aid in keeping the silver sequestered in the suspension that comes from the silver that is bleached out of the film.

    There will be more than just the EDTA; I would suspect there is also something else in it to reinvigorate the active bleaching agent. The other option is that the bleach is reactivated by oxiginizing it (thing fish tank bubbler) and the edta just keeps the building silver levels sequestered.

    For my C-41 I use a home brew C-22 80g/l K ferricyanide/ 20g/L K bromide bleach. I replenish with the same stuff at a rate of 45mL / 80 sq in. The early overflows from the replensihment I save and then when I need a farmers reducer I mix it 50/50 with aged fixer and maybe some water if I do not want to bleach the print too fast.
     
  3. Hologram

    Hologram Member

    Messages:
    135
    Joined:
    Oct 17, 2006
    Shooter:
    Medium Format
    One of the standard, low-toxic, rehalogenating bleaches used for Lippmann emulsions is based on ferric EDTA. It has extraordinarily good keeping properties – several years.

    For example:
    Fe-EDTA...............30g
    Kbr.......................30g
    acetic acid.........70ml
    (or sulfuric acid.10ml
    water.....................1L

    Alternatively, the Fe-EDTA can be replaced by 30g ferric (III) sulfate and 30g disodium EDTA.

    I guess for the much larger “photographic” grains you might have to increase the concentration of this bleach considerably.
     
  4. dancqu

    dancqu Member

    Messages:
    3,676
    Joined:
    Sep 7, 2002
    Location:
    Willamette V
    Shooter:
    Medium Format
    Well now that is interesting, Lippmann emulsions.
    Alternatively sodium bisulfate should do. That
    bleach may just do for prints. Dan