Pot Ferri/Brom instead of Farmers?

Discussion in 'B&W: Film, Paper, Chemistry' started by wilfbiffherb, May 9, 2013.

  1. wilfbiffherb

    wilfbiffherb Member

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    Hi,

    Just reading a fanastic book about darkroom techniques applied to the landscape by Eddie Ephraums and in it he uses farmers a lot to lighten areas that cant effectively be dodged. I dont have any farmers but i have pot ferri/pot brom. is this a viable substitue? obviously once its gone with farmers its gone but pot ferri brom can be redeveloped/toned...
     
  2. paul_c5x4

    paul_c5x4 Subscriber

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    Sure, it is viable to use a plain pot ferri/bromide bleach. Once you have the levels of bleaching you want, just give it a fix & wash as normal. All you are doing is separating the fix & bleach into two baths with the option of redevelopment if you go too far.
     
  3. pentaxuser

    pentaxuser Subscriber

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    Two questions out of curiosity: Couldn't you just use very diluted pot ferri and have some running water to play on the bleached bits once you get to where you want to be and then re-fix?

    How does the pot ferri and pot bromide work that's different from what I said above?


    Thanks

    pentaxuser
     
  4. Gerald C Koch

    Gerald C Koch Member

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    When you add potassium bromide to potassium ferricyanide you get what is known as a rehalogenating bleach. The silver is converted to silver bromide and so the bleached image can be redeveloped if you do not fix it. This is used with some toners and intensifiers as a first step. For plain bleaching you do not need the bromide. However in this case if you over bleach you cannot bring the image back.
     
    Last edited by a moderator: May 9, 2013
  5. Ian Grant

    Ian Grant Subscriber

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    There's another differance Pot Ferri/Br will lighten the highlights faster than the shadows, so is often used for slit toning. while Farmers reducer will lighten the shadows more which is what it was often used for.

    Beware versions of Farmers Reducer using Rapid fixer they aren't Farmers reducer at all and work far to fast. Farmers reducer uses plain Sodium Thiosulphate and Potassium Ferricyanide.

    Ian
     
  6. pentaxuser

    pentaxuser Subscriber

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    Thanks all and the difference between lightening highlights and shadows of the two compounds explains why at first glance Farmer's wasn't replaced by what seems a more forgiving bleaching system

    pentaxuser
     
  7. ronlamarsh

    ronlamarsh Member

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    This is the technique that Bruce Barbaum teaches in his workshops. He uses a very soft haired brush such as the ones used for Chinese calligraphy and a very dilute Pot Ferri and of course a small hose of gently running water. It gives a very controllable way of bleaching but like all bleaching it takes practice to keep it from getting out of hand. With this technique it also helps to dip it in the fixer periodically so you know where you are at.