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348Re: [PPLetterpress] Halftones

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  • Dan Mayer
    Jan 30, 2002
      Greetings all,

      Halftones and bitmap (computer-generated stochastic random dot ‹ a.k.a.
      diffusion dither bitmap ‹ whew!) can both be easily accomplished with
      polymer plates. The plates are highly receptive to fine detail. (polymer
      can accept more detail than the Vandercook's capability)

      The literature on Toyobo Printight Plates (Anderson Vreeland) suggest a
      halftone resolution at 150 dpi.

      Although printing 150 dpi on the Vandercook will be difficult because the
      plate will fill in. Roller adjustment, ink tack, and paper selection (that
      is smooth paper versus a textured paper) will also be an issue when printing

      Make test plates such as 65, 100, 110, 133 dpi and observe where the plate
      peaks out, that is, fills in.

      Bitmapping is also another possibility with polymer. I have had success with
      printing 300 dpi (computer dpi) bitmapped information. Higher resolution can
      also be attained for bitmapped line work.

      For plate processing (bitmap or not) I use a quasi-low-tech method utilizing
      a bank of 8, 24-inch long High Output UV florescent tubes (with vacuum draw
      sheet) and a brush for hand wash-out.

      For further reading on outputting bitmap from the computer, check out
      "Making Digital Negatives for Contact Printing" by Dan Burkholder.

      Happy Printing

      -- Dan

      Dan Mayer
      Book Arts Printer & Shop Manager
      Pyracantha Press
      School of Art
      Arizona State University
      Tempe, AZ 85287-1505


      on 1/30/02 6:17 AM, Katie Harper at knharper@... wrote:

      > Is anyone out there doing "real" halftones--ie, accurate, quality
      > reproduction of photographs-- via letterpress with polymer (or other)
      > plates? I'm interested to know if letterpress can compete at all with offset
      > in this area, given the right paper, inks, etc.
      > Katie Harper
      > Ars Brevis Press
      > Cincinnati, OH
      > 513-233-9588
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