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113Re: [PPLetterpress] Exposure/washout units

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  • Frank Cabral
    Sep 21, 2001
      Hello David,
      We use a Anderson Vreeland orbital washout unit. It is very simple and does
      not have many variables. It is basically exposing the properly dense
      negative, (4.0 at least, I like them digitally output of at least 1200 dpi)
      emulsion side down on the plate material for about 2.5 minutes, this is one
      of the areas where you can affect the plate. I find the MLD 145 plate
      material the best for type and where you need crisp edges I will use the
      softer plate material for printing solids. Once exposed the plate is
      attached to the magnetic orbital part of the unit and washed out with water
      for about 4 minutes. At one time I would wash it out for 2 minutes put the
      plate in the oven and dry it for 10 minutes and then wash it out for 2
      minutes then complete the drying for 20 minutes with a final exposure 4
      minutes to harden the entire plate. I have used this process with film that
      is not as dense or with very fine lines or small dots or where there is a
      lot of space between images. When I make a bad plate it is generally that
      the film was not dark enough, I exposed the wrong side of the film or the
      suction holding the kreen in place was not sufficient, all of this
      allowing to much light in to harden parts of plate that should be washed
      out. At one time a representative of AV suggested we put in vinegar in the
      washout water, at that time we had treated water, that worked fine until we
      put in a well and had the water filtered and softened which reacted with
      the vinegar and produced unstable plates, granular edges. I stopped using
      the vinegar and the problem vanished. It took a long time to figure that
      one out. I have only used this machine and have no comparison. I feel very
      confident in being able to produce excellent plates. Last summer I made
      about 230 8"x 10" plates of 16 pt text and had two bad plates, one I should
      have replaced the kreen sooner the other there was a speck between the
      negative and kreen which produced some broken letters. I will be interested
      in the experience of others with this and other machines.

      Frank
      cabral@...
      Nevada City

      dpwall@... wrote:

      >
      > I am interested in hearing some of the pros and cons of the various
      > machines as they compare to one another. Can anyone offer opinions in
      > this regard?
      >
      > Thanks,
      >
      > David Wall
      >
      >
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