The importance of Acid based STOP?

Discussion in 'B&W: Film, Paper, Chemistry' started by /dev/null, Nov 21, 2011.

  1. /dev/null

    /dev/null Member

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    The week I was wondering why you would use a STOP in development, and with STOP I am referring to the Amaloco S-10 Citric Acid stop I use. My 80ies photography guide says to use stop, but is quite unclear about why to use this acid stop.

    With Efke film I read to be very careful with stop. But why not with my Kodak TMAX100 or TMAX400? Feels like I am destroying the grain for some reason. So can't I just wash the film with water for about a minute and then fix instead of using this 30 seconds citric acid stop? Any pro's and contra's from the old skool developers?

    Thanks.
     
  2. Rick A

    Rick A Subscriber

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    You use an acid stop to neutralize the action of the alkaline developer and prevent the developer from carrying over to the fixer and contaminating it. Make sure you dilute the stop according to the mfg's specs. If the acid is too strong you risk a serious reaction when placing the film(or paper) into it.
    Some people believe that the emulsion on Efke film is prone to pinholes from this reaction. If this a concern, dilute the stop by an extra 50% for the film. I use an extra rinse step between the stop and fixer to extend the life of the fix. For Efke, I use a 30-60 second soak in the diluted stop followed by an immediate 30-60 second rinse with water and have never experienced pinholes in my emulsion, I shoot with Efke 120 and 4x5. This is my standard method with ALL my films, so I don't have any confusion in my DR.
     
  3. c6h6o3

    c6h6o3 Member

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    The main purpose of an acid stop is to protect the fixer. It's especially important with T-grain films as they tend to deplete fixer more quickly than traditional films anyway.
     
  4. bdial

    bdial Subscriber

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    With film, you can use water, and many of us do. Sometimes an acid stop can cause pinholes in very soft emulsions, Efke may be a film prone to that, IDK, it won't be a problem with Kodak or Ilford films though. In addition to stopping the developer immediately, a stop bath helps the fix to last longer.

    The problems you see in your Efke may be from other causes too, for example, reticulation caused by temperature shifts between solutions or the wash. Not sure what you mean by "destroying the grain", maybe you can elaborate?

    I use a water stop, for one minute with continuous agitation.
     
  5. markbarendt

    markbarendt Subscriber

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    The purpose of the stop is control development time and to a point to protect the fix.

    Either water or stop will protect the fix.

    The acid stop is faster at stopping the development process so you may want to adjust/shorten your development time just a bit if you switch.

    Water will work just fine but it takes longer.
     
  6. /dev/null

    /dev/null Member

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    OK, so basically an Amaloco acid stop, per water concentration as Amaloco advises should not really have a negative impact on my Kodak Tmax, Tri-X and Ilford films? And I can just continue in using it with these films? I use the Kodak TMAX fixer afterwards.
     
  7. markbarendt

    markbarendt Subscriber

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    Correct
     
  8. cowanw

    cowanw Member

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  9. /dev/null

    /dev/null Member

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    Thanks all for the information, this clarifies a lot.
     
  10. Роберт

    Роберт Member

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    Amaloco S-10 is nothing special. It's an oderless stop bath based on Citric Acid. Your regular dilution is 1+19 to reach an approx. 1,5% Citric Acid working solution. In this concentration you can also use it for Efke films. Concentrations over 2%-3% (Acetic Acid) can maybe have problems with softer emulsions like Efke/Adox.
    You can harden Efke films. You can do this during the fixer when using a hardener in the fix. But you can do it also earlier in the development stage. You can add a small amount of Formalin in the (Alkaline) developer. Not too many because then your base fog is going up. Formalin is very effective in this way but it's pretty crappy stuff. You need good ventilation, eye protection and gloves when working with this material. It's also used in the old type stabilizer of C41/E6 films. 0,5%-1% Formalin and the regular dose of wetting agent. Formaldehyde you can buy in the pharmacy in a concentration of normally 37%. 27ml of 37% in 1 liter destilled water is exactly 1% Formalin.