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11768Re: [PPLetterpress] fine lines breaking up on press?!?

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  • Steve Robison
    Jun 10, 2010
      Maybe it was the famous reference to "plastics" in the movie The Graduate that has us all brainwashed,but as an FYI footnote to Gerald's previous comment, note that some polymers are plastics, but certainly not all.

      Polymer just refers to macromolecules that have long strings of repeating structural units.

      For example, DNA, nucleic acid and proteins are all polymers and are some of the basic building blocks of life.

      Some naturally occurring polymers are shellac, amber, rubber and cellulose, all formed as part of the process and interaction of DNA and certain proteins.

      Some synthetic polymers are polyethylene, polystyrene, polypropylene, polyacrylonitrile, silicone, synthetic rubber, bakelite, neoprene, nylon, PVB, PVC, etc, many of them known commonly as "plastics"

      Photopolymer is a particular polymer that hardens when exposed to ultraviolet light, which makes it a wonderful substance for relief printing using a photographic process.

      But as previously mentioned, fine detail can only be held up by the atoms in the molecules underneath that fine detail, and sometimes the hardened photopolymer is not quite up to the task even if perfectly processed.

      Low relief plates, crisper initial images, better exposure times, better washouts will all help.. But if after all of that fails, try stronger molecules under the fine detail, like copper plates mounted on a steel base,for example. Notice I didn't say copper mounted to a wood base, since the irregularities of wood do not always have the fine tolerances needed for ultra fine detail. But copper on a solid base cut to fine tolerance works well, and copper will hold fine detail better than zinc or magnesium.

      So if photopolymer doesn't cut it after perfect processing, then think copper on a steel base as a possible alternative...giving you a sturdier molecular advantage. That's the way they used to do it for fine detail in the 1800's with great success, and those methods still work today...they're just less enviro friendly and sometimes a bit costlier...but not always. :-)

      Anyway, good luck with your efforts and results, remembering that there's always more than one way to put an image on to or in to a piece of paper...

      Best wishes,


      Steve Robison
      The Robison Press
      Belmont, CA
      (about 25 miles south of San Francisco and 30 miles north of San Jose

      --- On Thu, 6/10/10, Gerald Lange <Bieler@...> wrote:

      From: Gerald Lange <Bieler@...>
      Subject: Re: [PPLetterpress] fine lines breaking up on press?!?
      To: PPLetterpress@yahoogroups.com
      Date: Thursday, June 10, 2010, 12:44 AM

      Generally, when it is a photpolymer plate mounted on an appropriate
      base versus a photomechanical plate mounted on wood, it would be the
      former, hands down. Who makes iron plates? And what is it in the
      chemistry that would actually make one think photopolymer plate
      material is plastic?



      On 6/9/10 10:48 PM, Ed Inman wrote:

      #yiv1557694848 {font-family:Geneva, Arial, Helvetica, sans-serif;font-size:10pt;font-family:arial, sans-serif;background-color:#ffffff;color:black;}#yiv1557694848 p{margin:0px;}
      When it's plastic vs. iron guess which one wins (LOL).


      From: Scott Rubel

      If the first impressions are pleasing and then it breaks down, then it
      just must be the hardness of the plate.
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