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RE: [PPLetterpress] printing images on polymer plates

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  • Ludwig M. Solzen
    Liz Real continuous tone reproduction in print, still has to be invented. There have been numerous experiments, however, to accomplish a similar effect—in
    Message 1 of 5 , Jul 7, 2006
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      Liz

      Real continuous tone reproduction in print, still has to be invented. There
      have been numerous experiments, however, to accomplish a similar effect—in
      fact, all halftone (or autotypical) reproductions are such an attempt.

      The best results you get with intaglio printing, because of its intrinsic
      quality of taking and adding ink gradually, and hence printing at different
      densities at a time. That is, the screen dots—which (in conventional offset
      and letterpress halftones) otherwise build the image and its different tones
      of grey—in an intaglio screen are in no way relevant to the image itself:
      they are just there to help to keep the ink where it should be while inking
      (cleansing) the form. They do not show up in the print—or only a
      little—because the (dampened) paper, soaked with the ink of all those tiny
      dots, compensates for the screen. So, the smaller your dots, the better.

      The traditional way of making a heliogravure (which is the proper term for a
      photographic intaglio reproduction), is by exposing a sheet of paper, coated
      with a light sensitive emulsion, through (1) an intaglio screen, (2) the
      continuous tone photo positive one wants to reproduce. Afterwards this sheet
      is transferred unto a copper plate, which is subsequently washed and etched.
      The process is difficult and cumbersome and I am still looking for the exact
      formula for the emulsion. I did some promising experiments, though, with
      photopolymer plates.

      You could use aquatint resin powder for the screen, in case you had the
      right emulsion and would use copper — the resin cannot be applied unto a
      photopolymer plate, of course. Sure, you could scan an aquatint screen and
      use this scan as your ‘handmade’ intaglio screen. Too, you could use yet
      another type of screen. You cannot just use the printer’s screen, or one you
      apply in PhotoShop to the image, doing only one exposure afterwards. I made
      a typical intaglio screen, being composed out of little black squares, as
      tiny as the raster elements of the output device, about 21 µm, at a
      resolution of 3600 dpi, with one square being one pixel. Real litho film,
      that is. I could have output the screen myself, as well, on my 600 dpi laser
      printer, in which case the resolution of the digital image should have been
      600 ppi. The resolution is fine enough and lots of easier to handle while
      exposing than the 3600, but homemade transparencies are simply not dense
      enough for being used as a stop-out raster screen. If you do, make sure you
      print them with a laser printer, not with an inkjet.

      The inkjet, you could and should use for the second film needed, your image.
      This should be printed fine enough, e.g. with Pictorico, an Epson or yet
      another device yielding photorealistic images. Too, you could directly use
      your wash drawing made on a transparency or glass plate. If you would prefer
      to print a digital image, make sure it complies to the requirements which
      apply to all graphic imagery: proper ppi (2×lpi of output raster screen),
      right contrast, correct grey balance &c. The blacks (shadows) should be
      maximum 75 percent, the highlights minimum 5 percent. Best print grey or
      composite grey, that is no separated or other colour images. If you would
      use a laser printer, first convert your image to a 1bit-TIFF bitmap, using
      PhotoShop’s ‘Diffusion Dither’, at the highest resolution of your printer.
      (Inkjet screens are always stochastic, those of laser device are never (?).
      With ‘Diffusion Dither’ you delude the printer and have the software do the
      ‘stochastic’ RIP.)

      First expose the photopolymer plate through the raster screen film you made
      or got from your service bureau. (You can use this screening film over
      again, so worthwhile to have one made on real dense film indeed). Only after
      that, expose the plate through the transparency print of your image.
      Exposure times, as always, should be tried out. Now process the plate as you
      would for letterpress: wash out, dry and post-expose. Ink and print as a
      normal intaglio plate on your hand press.

      If you would still have some questions, I’m always pleased to be of service.

      Sincerely,

      Ludwig
    • Elizabeth Gross
      Real continuous tone reproduction in print, still has to be invented. There have been numerous experiments, however, to accomplish a similar effect—in fact,
      Message 2 of 5 , Jul 8, 2006
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        Real continuous tone reproduction in print, still has to be invented.
        There
        have been numerous experiments, however, to accomplish a similar effect—in
        fact, all halftone (or autotypical) reproductions are such an attempt.

        The best results you get with intaglio printing, because of its intrinsic
        quality of taking and adding ink gradually, and hence printing at
        different
        densities at a time.

        Elizabeth Ann Gross
        Deer Tree Press
        eahalegross@...

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      • Mark Attwood
        Liz, I too do mostly hand printed lithography, and some letterpress on a vandercook, and I think if you are looking for ways to get great washes, that
        Message 3 of 5 , Jul 12, 2006
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          Liz,

          I too do mostly hand printed lithography, and some letterpress on a
          vandercook, and I think if you are looking for ways to get great
          washes, that lithography, possibly using photo plates is the way to
          go. Letterpress just doesn't like tonal stuff! I have done some photo-
          litho stuff that we scanned in, and output stochaistic positives in 2
          greys and a black that worked really well, and looked "continuous
          tone" although it wasn't.

          Mark Attwood.
          The Artist's Press



          On 6 Jul 2006, at 05:23, eahalegross wrote:

          > I have just opened Deer Tree Press in Philadelphia, PA USA
          > Hello All. I print hand lithography from stones and aluminum
          > plates, letterpress - I have an
          > SP20, and monotypes including over-sized prints on a very large
          > etching press.
          >
          > My questions have to do with how to output negatives to give (the
          > impression of) continuous
          > tone prints using photo polymer plates.
          >
          > I want to make a ppplate using a wash drawing as the starting point.
          > I thought I could scan the drawing and then print it out as a
          > transparency.
          > How high a DPI can I use. Do I have to turn it into a bit map or
          > can I expose an aquatint
          > screen onto the plate over the image? Particular curves in Photoshop?
          >
          > Laser Printer? Inkjet?
          >
          > Has any one used Pictorico to print transparencies for this
          > purpose? It produces a half-tone
          > with very small dots with Inkjet. It appears that there is no dot.
          > (They are used a lot for
          > contact negatives for Non-silver photography.)
          > Thoughts or sources would be appreciated.
          > Thanks, Liz deertreepress
          >
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          >
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