Film Bleach pH = brown stain?

Discussion in 'Color: Film, Paper, and Chemistry' started by ZorkiKat, Oct 15, 2007.

  1. ZorkiKat

    ZorkiKat Member

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    If a ferric EDTA bleach goes alkaline, what happens to the film? Will it stain to the resulting negative? The 'chrome films I crossprocess come out like masked colour negatives when they should have 'clear' bases instead. I'm thinking that the home-brewed ferricEDTA bleach I'm using must be too alkaline. Don't have a pH meter to determine the pH of this bleach. Could this "mask" be iron stain? If this bleach is indeed slightly alkaline, will it cause this stain?
     
  2. Photo Engineer

    Photo Engineer Subscriber

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    The C41 and E6 bleaches should have a pH value of about 6.5 or so at 20 deg C.

    If they become alkaline, they can leave a brown stain.

    If the bleach is not active enough (stale or too dilute) it can leave a brownish stain on slides due to retained silver.

    Blixes sometimes leave a brownish stain on film if they are not strong enough.

    It can also be retained silver halide due to a bad fix. Re bleach and fix with wash and stabilze will fix this but will not fix stain from iron. There is a fix, but it is rather difficult to do.

    PE