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Thread: pre soak

  1. #11
    Drew Wiley
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    Sep 2008
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    SF Bay area, CA
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    10,557

    Re: pre soak

    There are endless arguments over all this. I am now at the point of ignoring the question. It suffices to state that I personally presoak everything briefly, whether film or paper. This not only helps the developer spread quickly and evenly, but pre-tempers the material to the correct working temp itself. This is very important
    with drum processing in particular, to get the inside of the drum itself to the correct temp. With sheet film tray processing, you want the emulsion to swell prior to putting it in the developer. pr the sheets might stick together at exactly the worst time. It's just a settled question for me.

  2. #12

    Join Date
    May 2014
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    Cote d'Azur France
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    80

    Re: pre soak

    Steve - thanks for that info, I would like to know what the ideal ph is for development of film. The water in our area is very hard, and while the impact on my negaitves may be minor, it would be good know. If there is any reading I can do on this can you point me in the right direction?

    Peter

  3. #13

    Join Date
    Jan 2014
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    Southwest
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    Re: pre soak

    Quote Originally Posted by 12pmc View Post
    Steve - thanks for that info, I would like to know what the ideal ph is for development of film. The water in our area is very hard, and while the impact on my negaitves may be minor, it would be good know. If there is any reading I can do on this can you point me in the right direction?

    Peter
    Ideal pH is an interesting concern. While pH is certainly a factor, buffers and alkalis are on your side.
    Peter,

    Generally speaking, potable water is suitable for photographic purposes. Working in the developer's favor are "buffers", a useful search term. An area library may have a copy of Modern Photographic Processing Volume 1 by Grant Haist. Informative and to the point is Chapter 5, The Function of Developer Constituents Development is a fairly complex heterogeneous reaction, the mechanism of which is not completely understood., K. S. Lyalikov

    Searchable Sleeping Pill #1
    https://archive.org/stream/TheTheory...ge/n7/mode/2up
    Searchable Sleeping Pill #2
    https://archive.org/stream/photograp...ge/10/mode/2up
    A local library system may also have other reference materials.

    What does your municipality report for water hardness? Third-hand Kodak information indicates water hardness between 40 and 150 mg/L is suitable for darkroom applications. With luck, your tap water is excellent for mixing with no concerns.

    The following is copied from
    http://motion.kodak.com/motion/uploa...2415_h2415.pdf

    Water Quality
    A supply of good quality water is very important to motion-picture processing. Although tap water may contain some impurities, most impurities have no photographic effect. Those you should be most careful of include large quantities of suspended organic matter, hydrogen sulfide, particles of finely divided sulfur, and soluble metallic sulfides. These can cause serious trouble with developers. Fortunately, these impurities are not common to most municipal water supplies.
    Processing Black-and-White Films page 15-7:
    Organic matter usually precipitates on mixing the developer, but biological growths and bacteria can thrive in developer solutions, forming a slime or scum on the walls of the tank. Certain types of these growths act on the sulfite in the developer and change it to sodium sulfide, a chemical which fogs the emulsion. Proper agitation and cleaning the developer tank frequently will prevent this. If alum carries into the wash water from the fixer, organic matter already in the water coagulates and settles on the film. You can avoid this by filtering the water, or by adding boric acid to an acid fixing bath (up to a maximum of 15 grams per litre).
    Extremely hard water may produce a finely divided precipitate when you mix the developer solution. The precipitate usually settles on standing, but even if it remains in suspension, it has no adverse photographic effect. If the precipitate is objectionable, add KODAK Anti-Calcium or Quadrofos. You may also see a fine precipitate when you use certain developers even though they were clear when mixed. This is normal and does not indicate poor mixing or impure water. Again, it has no adverse photographic effect.
    A chemical analysis of the water supply usually reveals very little concerning its photographic usefulness. The most useful test is to prepare the required photographic solution with the suspect water sample and actually try it. Compare your results with those obtained with the same solution prepared with distilled water. In most cases, both of the solutions will be alike in their photographic effect, even if not in appearance."

  4. #14
    John Olsen
    Join Date
    Jan 2012
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    Whidbey Island, WA
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    481

    Re: pre soak

    Quote Originally Posted by 12pmc View Post
    Thank you all - connected to the water question, does water hardness have an impact on the development of the negative?
    Under extreme conditions, definitely yes. Our mountain well had really hard water that could turn emulsions to muck. I used reverse osmosis water from the store for mixing chemicals and rinsing film. I don't know about the effects of moderately hard water.

  5. #15

    Join Date
    May 2014
    Location
    Cote d'Azur France
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    Re: pre soak

    Thanks for all your input and Ifpf your references. I am not sure what our local water hardness is, but do not think is it is that hard..

    Peter

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