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  1. #11
    Thomas Bertilsson's Avatar
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    Quote Originally Posted by Rick A View Post
    The malady the OP is obviously refering to is called "cupping". The cause is the emulsion layer being a different substance than the base of the film, when dried it shrinks more than the base material. I have a feeling that some with this excessive problem have probably left the film in liquid for longer than necessary, causing more expansion initially, resulting in excessive shrinkage upon drying. I shoot Chinese film that most complain that it cups and curls, but have personally experienced minimal signs of it, Foma does exhibit some tendency, Ilford, Fuji, and Kodak almost none in my experience.
    Your geographical location makes a huge difference, because it's humidity related. I live in Minnesota, which has some of the biggest differences in humidity in the world, comparing summer to winter. Bone dry like the desert in the winter, and often 90% or more in the summer.

    In the summer my negatives dry flat, and in the winter they don't.
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  2. #12

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    Dear brianentz,

    Just ignore it. The film will flatten nicely over time. If it really bothers you, follow the advice from Rick A. It will help.

    Neal Wydra

  3. #13

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    Quote Originally Posted by Thomas Bertilsson View Post
    Your geographical location makes a huge difference, because it's humidity related. I live in Minnesota, which has some of the biggest differences in humidity in the world, comparing summer to winter. Bone dry like the desert in the winter, and often 90% or more in the summer.

    In the summer my negatives dry flat, and in the winter they don't.
    Thomas is correct and that is what I experience in Finland. The relative humidity of the air in the room when drying the film needs to be as near as possible to 50%. In winter in Finland, the dry air brought into the house and warmed up to 20c has a relative humidity of 20 to 25%. The film curls like hell.

    Flattening the sleeved film under a pile of books after it is TOTALLY dry can improve it a lot. Beware that the film can get damaged if still slightly damp, because the pressure "embosses" the texture of the sleeve into the emulsion.

    Dave

  4. #14
    Thomas Bertilsson's Avatar
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    Quote Originally Posted by oldfaithful58 View Post
    The relative humidity of the air in the room when drying the film needs to be as near as possible to 50%. In winter in Finland, the dry air brought into the house and warmed up to 20c has a relative humidity of 20 to 25%. The film curls like hell.
    For me, 'curling like hell' means a roll of 35mm Tri-X cups around the entire length of the film a good 120-150 degrees, almost half a circle. Not as extreme as the attached picture, but really close.

    In storage it takes my negatives about a month to flatten to the point that I can put them in a scanner and scan them. The enlarger is obviously better since the neg carrier flattens them nicely, but sometimes they can be tough to align without somehow damaging them.
    Attached Thumbnails Attached Thumbnails semicircle.png  
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  5. #15
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    If your humidity is really low, your negatives will dry very quickly. This can lead to cupping. If you're talking about curling (spiral form curls), then you're failing to dry the film with a weight to straighten it.

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