Liquid emulsion problem - advice needed!

Discussion in 'Silver Gelatin Based Emulsion Making & Coating' started by gandolfi, Dec 2, 2013.

  1. gandolfi

    gandolfi Member

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    I have a problem!
    Or rather my students have a problem, and I can't figure it out so hence this post....

    When printing the emulsion (FOMA's stuff) everything looks good in the developer - and also in the rinse (stop, which is water), but the second it comes in fixer, be it hardening or hardening, the image turns almost totally black....

    I don't really get it, as some have this issue - some not. It rarely happens to me.

    And today two students made prints - from the same batch of emulsion - same surface - same chemistry... the one got fine looking images - the other the balck "version"...

    How can this happen?

    Educate me please...
     
  2. MDR

    MDR Member

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    What was the surface, was the coating applied in the same manner, was it dried for the same amount of time and most importantly did they use the same fixer at the same time or did the person with the good results use the fixer before the person with the bad results (exhausted fixer and sulfur build up could be a cause for the image going black)
    Come to think of it I had some problems with the foma emulsion on wood.

    Good luck
     
  3. Hexavalent

    Hexavalent Subscriber

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    Try a longer time in the stop, and acid stop. Being a liquid emulsion, it's probably not hardened, and holds a lot of dev. Carry-over into the fix can make an emulsion foggy, give it a strange colour tint, or make it go black.
     
  4. gandolfi

    gandolfi Member

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    MDR: it has happened both on paper and on wood. I thought about the exhausted fixer and we have made fresh fix - with same result...

    Ian: Yes - we normally use tap water - and that will exhaust rather quickly... I'll make some tests with acidic stop...

    The thing that bothers me most is, this almost never happens to me.... (same equipment used...)

    Thanks.
     
  5. MDR

    MDR Member

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    Maybe the emulsion was fogged after the stop bath, someone using the enlarger while she/he carried the material from one tray to the other. Also as hexavalent said liquid emulsion might hold more developer and the stop bath was not long and or strong enough to stop the development process. Wood holds probably even more chemistry than paper. You might wanna try the Rollei/Maco emulsion hardener it's put into the developer instead of the fixingbath. Use the stopbath for twice the recommended time for normal paper (might attack the emulsion so pre-hardening is recommended)
    Again good luck.
     
  6. jnanian

    jnanian Advertiser Advertiser

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    hi gandolfi

    were you there when they made the prints
    and they blackened ?

    maybe it isn't fixer they are putting it into but something else ..
    i processed 7 plates a few months ago in alum hardener by mistake
    so i know accidents can happen :smile:

    john
     
  7. gandolfi

    gandolfi Member

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    hardener is provided with the Foma emulsion - I never use it... (it's a total no-go if using the papers for bromoil prints..)

    I think the issue could be in the thichness of the papers - the students (and me) are using the same emulsion - same developer - same stop and fix... and it always happens after the stop/rinse, so the difference between us has to be how we coat our papers - some thinner than others.... And if thick, then the stop might be insufficient..
     
  8. gandolfi

    gandolfi Member

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    I know I know - but here I am sure the process was followed according to plan... (almost.. :wink: )
     
  9. MDR

    MDR Member

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    It seems that you've found the culprit different coating thickness and not enough stop bath time-

    Check out the brushes different brushes will soak up different amounts of emulsion and cause different layer thickness and more importantly if a change in the stopbath regimen doesn't help you might have contaminated brushes.

    Love your work
    Good luck to you and your students
     
  10. pasiasty

    pasiasty Member

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    I recently faced similar (yet not the same) issue with Foma emulsion: I double coated watercolour paper, exposed contact prints on it - while in developer or the in a stop bath, the image looked quite well, greys and black were even; once put into fixer, brush strokes and paper texture became very visible. And yes, the picture got a bit darker (not blackened, anyway), but that's expected.

    I wonder if triple (or more) coating may help. The paper is quite coarse.

    I use acidic stop bath, also because the watercolour paper seems to be pH-balanced using some alkali - it hisses when poured into acidic bath. Next time I'll buy better one... Anyway, if it's not enough stopping in water that causes blackening, you may try acidic.

    Gandolfi: the two students of you, did they both expose and develop the prints the same way?
     
  11. Photo Engineer

    Photo Engineer Subscriber

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    Generally, hand coatings are quite a bit thicker than production coatings. This means more carryover of chemistry and thus more developer can get into the fix, especially if the stop is just a tray of water. Running water is better and an acid stop is the best.

    It also depends on the pH of the fixer. An acid fixer with hardener is best.

    PE