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Photopolymer problem

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  • thomas krakowiak
    I am currently producing photopolymer plates for students for their projects in the letterpress course here at UNR. Up to this time, I have only done images
    Message 1 of 3 , Jan 28, 2002
      I am currently producing photopolymer plates for
      students for their projects in the letterpress course
      here at UNR. Up to this time, I have only done images
      and graphics. My efforts with text blocks are still in
      the experimental stage but there is light at the end
      of the tunnel.
      I use a home made exposure unit with six 15 watt
      black light bulbs with vacuum. Exposure time 4
      minutes, manual wash out with lukewarm to warm running
      water and Becker's brush. Dry with hair dryer and
      harden under same light for 5 minutes.
      Plate material is steel backed HX 145 from Anderson &
      Vreeland.
      The results are great whether heavy line art or very
      fine lines. No problem with printing on the Vandercook
      Univ.I. Students usually run 25 to 50 copies of each
      project. I'm happy, the students are happy and the
      instructor is happy.
      So, what is the problem?
      I've used CODA [double side tape], spray
      adhesives,magnetic sheets attached to wood blocks and
      sometimes all of the above together.
      No matter what I use, the plates begin to curl up at
      the sides in a few days. Fortunately this is after the
      projects are completed.
      When the image is a simple line drawing with open
      spaces within the image, the plate stays flat. However
      if there is an abundance of solid surfaces within the
      image, then the plate takes on a life. Thus using the
      plate again at a later date is at best difficult if
      not impossible. Help!

      Tom Krakowiak jaktamtsk@...
      The Black Rock Press
      University Library/322
      University of Nevada, Reno
      Reno, NV 89557-0044



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    • edinman
      I also have had the edges of steel backed plates curl up on me, but in my case it was from using too much pressure on the press combined with the rubberized
      Message 2 of 3 , Jan 28, 2002
        I also have had the edges of steel backed plates curl up on me, but in my
        case it was from using too much pressure on the press combined with the
        rubberized magnetic bases, which tend to "give" a little at the impression
        point when pressed.
        I'm otherwise at a loss as to why the plates would start to curl if they are
        steel backed--but you might try storing them in heavy cardboard envelopes
        between flat surfaces (such as books under light pressure) to keep them
        flat.
        Ed
      • Joel Benson
        Sounds to me like it has something to do with the polymer shrinking, if it only happens on heavy images. This hasn t happened to me, so I can only guess as to
        Message 3 of 3 , Jan 28, 2002
          Sounds to me like it has something to do with the polymer shrinking, if
          it only happens on heavy images. This hasn't happened to me, so I can
          only guess as to remedies. Did you try a more thorough drying of the
          plate? A longer post exposure? A wetter/drier/warmer/cooler storage
          facility?
          Might be time to refer to the technical specs for the material you are
          using, to see where you might be getting your variance.

          Joel

          Joel Benson
          Dependable Letterpress
          San Francisco

          -----Original Message-----
          From: edinman [mailto:edinman@...]
          Sent: Monday, January 28, 2002 4:27 PM
          To: PPLetterpress@yahoogroups.com
          Subject: Re: [PPLetterpress] Photopolymer problem


          I also have had the edges of steel backed plates curl up on me, but in
          my
          case it was from using too much pressure on the press combined with the
          rubberized magnetic bases, which tend to "give" a little at the
          impression
          point when pressed.
          I'm otherwise at a loss as to why the plates would start to curl if they
          are
          steel backed--but you might try storing them in heavy cardboard
          envelopes
          between flat surfaces (such as books under light pressure) to keep them
          flat.
          Ed



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