Formula for Hardener?

Discussion in 'B&W: Film, Paper, Chemistry' started by amuderick, Apr 1, 2008.

  1. amuderick

    amuderick Member

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    I am doing B&W reversal processing and just tried using thiourea to develop sepia-toned slides. SInce I use a permanganate bleach, I'd like to harden the emulsion after the thiourea redevelopment and just before washing. A test clip dipped in Kodak Rapid Hardening Fixer darkened the film and led me to believe that I shouldn't drop my whole roll into this.

    Is Fixer a no-no for silver sulfide?

    If I wanted to mix a hardening solution without fixer in it, how would I do this? Potassium Alum? Chrome Alum? Can I use diluted acetic acid to acidify the solution? Any other ingredients?

    I'd like to avoid formalin unless that is really the best option. I'm trying to keep my darkroom limited to acutely toxic chemicals only ;-)

    Thanks!
     
  2. Lowell Huff

    Lowell Huff Inactive

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    DO NOT DO IT! Hardening the film in mid process is not part of the system. How did thiourea become the second developer?
     
  3. Alessandro Serrao

    Alessandro Serrao Member

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    Potassium alum in an acidified media is good. Remember the pH must be acidic (acetic acid is good - don't use citric acid) because potassium alum works only in acidic solutions.

    There's a Tetenal hardener in the european market, readily available.

    If you use a sulfide redeveloper (thiourea or sodium sulfide) an hardener/fixer is not required.
     
  4. amuderick

    amuderick Member

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    Alessandro, thank you.

    By what means does the thiourea harden the emulsion?

    I did notice it was much more resilient than using a standard light exposure + redevelopment.

    Also, do you have any experience in altering the tone of the sulfide by changing the alkalinity of the solution (i.e. varying the amount of sodium carbonate)?

    Thanks!
     
  5. CBG

    CBG Member

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    Your thiourea toning positives process sounds interesting. As you work through the various parts, would you be amenable to posting some sort of summary of the steps - formulas, times, temperatures etc?

    Thanks!

    C
     
  6. Alessandro Serrao

    Alessandro Serrao Member

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    Unfortunately I don't use thiourea for the very same reason I don't use dichromate: because I believe it's carcinogenic.

    I used sodium sulfide but haven't played much with the alkalinity of the solution (I don't have a pHmeter handy).

    However, using half strenght permanganate solution works equally well as a bleach and does not damage the film emulsion.