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2152Re: Water on plates

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  • E Roustom
    Nov 3 6:56 AM
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      > but once exposed and dried and re-exposed so the
      > plate is fully hardened and ready to print, there is little or no effect of
      > water ... on the plate

      There is no question about it. The plates are water sensitive even after
      exposure and hardening. If you've experienced otherwise you've been lucky.
      The moisture content of the plate material is what gives it its working
      charecteristics. Too little, and the plate curls and craks, too much at it
      is too soft to be effective.
      From experience: An old plate that is curled up (because it's lost its
      moisture) can be flattened by soaking. Droplets of water from cleanup mark
      plates (still on press), by swelling, and these little marks do show up in
      print. Paper that is too damp (poor dampening technique followed - another
      subject altogether) will moisten the plate and cause the paper to adhere to
      the plate. Old dry plates left to soak too long fall apart. Otherwise,
      solvents from acetone to soy-solve do nothing to damage the plates.
      Keeping the plates stable for long periods of storage is important.
      Moisture sealing plastic wrap like Saran brand, or ziplock bags, or both
      must be used, sometimes a drop of water in the package is needed, depending
      on the weather at time of storage.

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