hca replacement

Discussion in 'B&W: Film, Paper, Chemistry' started by RalphLambrecht, Jul 26, 2012.

  1. RalphLambrecht

    RalphLambrecht Subscriber

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    i was wondering, if it makes sense to replace the hypo clrearing agent bath with something closer to sea ater, not eliminating the sodium sulfite (2%)but adding actual sea salt(3.5%)and maybe somemagnesium chloride(0.25%)just a thought, for dis cussion.
     
  2. Gerald C Koch

    Gerald C Koch Member

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    Kodak did extensive tests with various salts and found out that sodiun sulfite was the most effective. IIRC, Agfa tried sodium chloride for a short while then sodium carbonate and finally sodium sulfite.
     
  3. Rick A

    Rick A Subscriber

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    Acording to Kodak, sea water for washing prints or film will save about 30% of wash time. They still recommend the use of HCA.
     
  4. Ian Grant

    Ian Grant Subscriber

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    Agfa always recommended Sodium Carbonate right up to their demise.

    Ian
     
  5. Jean Noire

    Jean Noire Member

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    Hello Ian,
    Is it possible for you to give concentration of carbonate that is suitable for use as clearing agent?

    Jean
     
  6. Gerald C Koch

    Gerald C Koch Member

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    Ian

    You are right I should have checked my notes before mentioning Agfa but I was in a hurry and didn't want to dig them out.

    However from my freshly dug out notes --

    Agfa recommended a 2% solution of anhydrous sodium carbonate. For single and double weight papers, wash the prints for 10 minutes. Then soak the prints for 10 minutes in the working solution with frequent agitation. Finally, wash the prints for an additional 5 minutes. Useful capacity is 100 8x10 prints per gallon of working solution. In any case, the used working solution should be discarded after 24 hours.

    Jerry
     
    Last edited by a moderator: Jul 27, 2012
  7. RalphLambrecht

    RalphLambrecht Subscriber

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    i gather ,the recommendations was identical to sodium sulfite...2%, which is interestinglyvery closely matchingthe global average of sodium chlorideat about 3%.My question again would a combination of different salts work better than hca alone?
     
  8. AndreasT

    AndreasT Member

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    Somewhere on this sight I once saw a list of different salts (sodium sulfite, Sodium Carbonate etc.) and how effective they are in washing. Where on this site I do not remember.
    It may have been Henk Rolfsa who suggested using 3% Sodium Carbonate and 1% sodium chloride (sea salt). However I am not sure about this.
    Somewhere else I once read that a combination of different salts improve the washing performance of a wash aid.
    Although the sodium chloride must be removed completly because the chloride may damage the photo over time.
     
  9. RalphLambrecht

    RalphLambrecht Subscriber

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    toobad, you can't remembr. i am very inetrestedto find out, but i will conduct my own washing tests regardless!
     
  10. john_s

    john_s Subscriber

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    I have read some posts, probably at rec.photo.darkroom before it went feral, by Richard Knoppow, citing Kodak research describing experiments that eventually showed that sodium sulphite was the best wash aid. As you know in Kodak HCA its pH is adjusted by moderately acidic metabisulphite.

    Agfa used to recommend carbonate but I think the relatively high pH of it can be a disadvantage to the paper emulsion because it softens it. It also might be not at an optimum pH for best rinsing. Isn't there a pH (the pH of Kodak HCA) where the gelatin is in some optimum state for fastest washing?