Selenium Toning w/ KHCA

Discussion in 'B&W: Film, Paper, Chemistry' started by Ray Rogers, Apr 24, 2008.

  1. Ray Rogers

    Ray Rogers Member

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    I was reading where someone said that on a box? of KHCA it was reccommended to add KHCA to KRST when selenium toning...

    Can someone provide an explanation for this combination?
    perhaps even a scan of those instructions?!!

    I do not recall seeing it on any of my pkgs of KHCA...
    Did something change?

    What is the logic behind the mixture?
    Any opposing views?

    Thanks!
     
  2. Doremus Scudder

    Doremus Scudder Member

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    Ray,

    Many used to use selenium toner mixed with the washing aid to eliminate a step in the processing. However, this is wasteful; the wash aid exhausts much more quickly than the selenium toner. If one wanted to keep the advantage of the wash aid, one would have to discard a lot of active toner, something I find not only wasteful, but environmentally irresponsible. There are enough heavy metals contaminating our waters and soils (not to mention our food!) already.

    I use my selenium toner over and over by 1) adding more stock solution to replenish and 2) filtering out the black precipitate that forms. I have two one-gallon containers with different working dilutions that have been going strong this way for over three years. By re-using the toner, the selenium I buy goes into the prints, not the waste water. My total discarded selenium, excepting that that is washed out of toned prints, is, for practical purposes, zero.

    The wash aid I use in a separate step, immediately after the toner. I find that it does not add a lot to my overall processing time since I usually tone large batches, and there are prints in the toner and the wash aid at the same time except for the very last few.

    My recommendation: Save your toner and re-use it. It's cheaper as well as more environmentally friendly. Use your wash aid separately, paying attention to the capacities so you do not overuse it.

    Best,

    Doremus Scudder

    www.DoremusScudder.com