over/under bleaching

Discussion in 'Color: Film, Paper, and Chemistry' started by futile1981, Jun 16, 2012.

  1. futile1981

    futile1981 Member

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    I develop my 35 mm film at home, mostly using c-41 Tetenal chemicals.


    I'm trying to figure out what exactly is the effect of under and over bleaching. What would happen if my bleach is not strong enough or my bleaching time is not enough or my bleach is too cold? What about the opposite?


    What's the difference when you look at the negatives?
     
  2. Photo Engineer

    Photo Engineer Subscriber

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    Underbleaching can cause higher grain and dull colors. It can also cause higher contrast. This is due to the fact that the retained silver adds a neutral density overall to the image and it consists of extra particles besides the dyes.

    You cannot overbleach in any practical sense. After bleaching is done, nothing takes place. You can soften the negative by keeping it in hot water too long.

    PE
     
  3. Ian Grant

    Ian Grant Subscriber

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    Under bleaching leaves silver in the colour film emulsion, you can't over bleach (within reason), so it's better to err on the cautious side. Bleaching is to completion.

    If you leave silver in a negative or transparency it'll appear grainier and there will be an impact on colour quality.

    Tetenal chemistry is very good so just go by their instructions, bleach or bleach fix likes oxygen so a good vigorous shake in a partially full bottle helps regenerate it.

    Ian
     
  4. polyglot

    polyglot Member

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    Google for "bleach bypass" to see the effect of severe underbleaching.
     
  5. futile1981

    futile1981 Member

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    Thanks PE, Ian and Polyglot! Alright, so basically there's no such thing as over-bleaching, so I should basically only worry about not insufficient bleaching...

    Thanks again

    Reza
     
  6. EdSawyer

    EdSawyer Member

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    For negs that may have been under-bleached, and fixed/rinsed/etc. - is it possible to re-bleach them to get the residual silver out and brighten the colors? Or is that not an option once it's been fixed?

    thanks!
    -Ed
     
  7. Photo Engineer

    Photo Engineer Subscriber

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    Prewet, bleach, wash, fix, wash and stabilize, and you should completely fix the problem.

    PE
     
  8. harragan

    harragan Member

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    I recently tried the bleach-bypass process and certainly got some of the expected results - muted colours and increased grain. Something else I experienced was an increase in residue on the film after drying. I am not sure that the process I used and the outcome are connected but that was the only difference that I can put my finger on. The same water, temperature, etc., but an increase in something that has left some of the negs unusable. Is this a likely outcome or should I be looking elsewhere for the problem? I have since washed the negs again - water and then water & photoflo for good measure but it didn't make any difference.

    Thanks in advance,

    Stuart