Loading ...
Sorry, an error occurred while loading the content.

Re: another possible factor in exposing plates

Expand Messages
  • bielerpr
    Dear Marnie What kind of processing unit are you using? I m a bit confused by this without knowing that. Most of the industrial plate processing machines do
    Message 1 of 11 , Jan 7, 2002
    View Source
    • 0 Attachment
      Dear Marnie

      What kind of processing unit are you using? I'm a bit confused by
      this without knowing that.

      Most of the industrial plate processing machines do use a rack of
      lights. So while directly over the plate, light is also being brought
      in at an angle. The angle of incidence is not a factor as it would be
      with photo silkscreen, however. Usually a translucent material (virgin
      vinyl), rather than a transparent (acetate) drawn-down sheet, ensures
      proper adhesion of film negative to plate during exposure. This helps
      prevent "offsetting" from the light source.

      Exposure should not be through transparent materials because they refract
      the light. But to some extent, halation is necessary to create the proper
      shoulder. The molecular structure of the polymer changes, the strands
      lengthen and crosslink. This makes them insoluable. It does not technically
      harden them. After washout and drying, the plate again needs to be exposed
      to ensure that all the polymer has been altered. I have not encountered any
      problem processing halftones that could not be attributed to the inital
      creation of the halftone itself, it, poor contrast, improperly sharpened, etc.

      We've used high intensity photo lamps for exposing photo collotype plates
      (photo sensitive gelatin on glass) but that's a different animal entirely.
      Various photo lamps produce a quite intense and focused light. Photopolymer
      needs a standard exposure rate (as provided by the configured rack of lights)
      at a variable exposure time. For halftones you need longer exposure times,
      though if they need to be sharpened a bit you can back off for a bit "crispier"
      result. Any standard machine will process 150 line screens. though it takes
      great care to "print" them successfully with the letterpress process.

      Don't know if this is quite the response that will help you but...

      Gerald


      --- In PPLetterpress@y..., "Marnie Powers" <mpowers@l...> wrote:
      > Hi all-
      >
      > I'm new to the list, and I'm unsure if this question has already been
      > raised. Has anyone considered the validity of a single light source? I
      > know that the exposure must be directly perpendicular to the plate so
      > that light does not pass through the open areas of the negative at an
      > angle, thus producing slabs on the sides of the relief areas verses a
      > hard edge. Would a single light source such as a metal hallide lamp
      > produce crisper results? That's what the printmaking stuido here at the
      > University of Utah is using for polymer and screenprinting. We (at the
      > letterpress shop) continue to use a multi-bulb black light blue
      > flourescent unit. Works great for type and line work, but not so well
      > with fine halftones. As a photographer, I've been doing a lot of
      > photographic exposures with tight line screens-- a serious challenge.
      > Boy do I hear you in regards to the plates headed straight to the waste
      > bin. I'd be interested in anyone's thoughts on this issue.
      >
      > Marnie
      > Marnie Powers-Torrey
      > Studio Manager
      > Book Arts Program
      > J.Willard Marriott Library
      > (801)585-9191
    • Mark Attwood
      Marnie wrote: Would a single light source such as a metal hallide lamp ... Marnie, I used a metal halide 5kw unit for exposing plates for some time before I
      Message 2 of 11 , Jan 9, 2002
      View Source
      • 0 Attachment
        Marnie wrote:

        Would a single light source such as a metal hallide lamp
        > produce crisper results?

        Marnie,
        I used a metal halide 5kw unit for exposing plates for some time before I
        got the multiple bulb fluorescent unit that I now use. My exposure times
        were VERY long (about 20 min) despite the power of the unit. After some
        research I learned that the polymer plates use a slightly different
        frequency of UV light to the metal halide, and this is where the UV
        fluorescent tubes have their wavelength.

        my 2c worth,


        Mark Attwood

        The Artists' Press
        Box 623
        Newtown
        2113
        South Africa

        Tel. +27 11 836 5474
        fax. +27 11 836 6858
        mark@...


        ----------
        >From: "Marnie Powers" <mpowers@...>
        >To: PPLetterpress@yahoogroups.com
        >Subject: [PPLetterpress] another possible factor in exposing plates
        >Date: Mon, Jan 7, 2002, 5:13 pm
        >

        > Hi all-
        >
        > I'm new to the list, and I'm unsure if this question has already been
        > raised. Has anyone considered the validity of a single light source? I
        > know that the exposure must be directly perpendicular to the plate so
        > that light does not pass through the open areas of the negative at an
        > angle, thus producing slabs on the sides of the relief areas verses a
        > hard edge. Would a single light source such as a metal hallide lamp
        > produce crisper results? That's what the printmaking stuido here at the
        > University of Utah is using for polymer and screenprinting. We (at the
        > letterpress shop) continue to use a multi-bulb black light blue
        > flourescent unit. Works great for type and line work, but not so well
        > with fine halftones. As a photographer, I've been doing a lot of
        > photographic exposures with tight line screens-- a serious challenge.
        > Boy do I hear you in regards to the plates headed straight to the waste
        > bin. I'd be interested in anyone's thoughts on this issue.
        >
        > Marnie
        > Marnie Powers-Torrey
        > Studio Manager
        > Book Arts Program
        > J.Willard Marriott Library
        > (801)585-9191
        >
        >
        > To post a message to the membership, send an email to
        > PPLetterpress@yahoogroups.com
        >
        > To log on to the groupsite (confirmed Yahoo ID required), go to
        > http://groups.yahoogroups.com/group/PPLetterpress
        > [copious reference sources can be found onsite in Bookmarks (URLs),
        > Database (tables), Files (documents), and Messages (archives)]
        >
        > Encountering problems? send an email to
        > PPLetterpress-owner@yahoogroups.com
        >
        > To unsubscribe, send an email to
        > PPLetterpress-unsubscribe@yahoogroups.com
        >
        >
        >
        > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
        >
      • Marnie Powers
        Mark, Thanks much for the information. Do you have any details on the specific UV frequency of metal halide verses flourescent, and the ideal frequency for
        Message 3 of 11 , Jan 9, 2002
        View Source
        • 0 Attachment
          Mark,

          Thanks much for the information. Do you have any details on the
          specific UV frequency of metal halide verses flourescent, and the ideal
          frequency for exposing photopolymer plates? If so, I'd be interested in
          seeing it.

          Best,

          Marnie
          Marnie Powers-Torrey
          Studio Manager
          Book Arts Program
          J.Willard Marriott Library
          (801)585-9191
        • Marnie Powers
          Gerald- The information that you provided was very interesting. I m somewhat familiar with the collotype process and know photosilkcreen fairly well. I realize
          Message 4 of 11 , Jan 9, 2002
          View Source
          • 0 Attachment
            Gerald-

            The information that you provided was very interesting. I'm somewhat
            familiar with the collotype process and know photosilkcreen fairly
            well. I realize these are birds of a different feather.

            To respond to your query about our exposure unit: it's a handmade job
            with a powerful vacuum accompanied by the translucent vacuum film
            that Gene Becker sells. The light source is six black light blue
            flourescent bulbs. There's about an inch between the surface to be
            exposed and the bulbs. Works very well except for high resolution
            photographs. Or rather, I do very well except with high resolution
            photographs.

            How I make the negative:

            Scan a 35mm slide or negative at @1200 dpi. Especially if it's low
            contrast, I play around with the curves in photoshop, condensing? the
            values somewhat (move the two points at either end of the diagonal
            inward so that I have a "new" diagonal line that runs directly parallel
            to and above the "original" one). It seems that I loose less detail this
            way then when I change the contrast/brightness, while still acheiving
            a denser negative with a little less tonal range. I have the image output
            on imagesetting film with a stochastic screen at "80". The difficutly is
            that the stochastic screen (as I understand it anyway) does not directly
            translate to lpi. With lower resolution photos the results are excellent.
            Using a negative produced in the darkroom with a tradition halftone
            screen, the results are excellent. I'm just trying to push the process a
            bit further.

            Maybe the dot gain is just too great on the letterpess. Or maybe when
            the dots get too small, the relief in the plate is not substantial enough.
            I've been able to do very high resolution/low contrast/high detail
            work with photopolymer plates printed intaglio, that I keep wanting
            the same to be possible with letterpress.

            I'd very much appreciate your (or anyone else's) feedback on how I'm
            dealing with these chanllenges...

            Best,

            Marnie
            Marnie Powers-Torrey
            Studio Manager
            Book Arts Program
            J.Willard Marriott Library
            (801)585-9191
          • bielerpr
            Dear Marnie Here s a useful page with a lot of links re: the halftone process http://halftones.info/ For further ref this is in Bookmarks under Tech Info
            Message 5 of 11 , Jan 9, 2002
            View Source
            • 0 Attachment
              Dear Marnie

              Here's a useful page with a lot of links re: the halftone process

              http://halftones.info/

              For further ref this is in Bookmarks under Tech Info

              Gerald
            • Katie Harper
              ... I m unfamiliar with the term stochastic screen. Can you explain what this is? Thanks. Katie Harper
              Message 6 of 11 , Jan 9, 2002
              View Source
              • 0 Attachment
                > From: "Marnie Powers" <mpowers@...>
                > Organization: Marriott Library
                > Reply-To: PPLetterpress@yahoogroups.com
                > Date: Wed, 9 Jan 2002 11:29:26 -0700
                > To: PPLetterpress@yahoogroups.com
                > Cc: vhindley@...
                > Subject: [PPLetterpress] Re: another possible factor in exposing plates
                >
                > I have the image output
                > on imagesetting film with a stochastic screen at "80". The difficutly is
                > that the stochastic screen (as I understand it anyway) does not directly
                > translate to lpi.


                I'm unfamiliar with the term "stochastic" screen. Can you explain what this
                is? Thanks.

                Katie Harper
              • Marnie Powers
                Hi Katie- I m willing to explain the stochastic screen to the best of my ability. As I understand it, it is not a random screen. Under a loupe it looks very
                Message 7 of 11 , Jan 9, 2002
                View Source
                • 0 Attachment
                  Hi Katie-

                  I'm willing to explain the stochastic screen to the best of my ability.
                  As I understand it, it is not a random screen. Under a loupe it looks
                  very similar to the grain of photographic film and paper. The screen
                  applies a spattered pattern to the image, the dots occurring more
                  frequently in dark areas than in the light areas. In terms of fooling the
                  eye into thinking it's seeing grayscale, stochastic is the most effective
                  screen currently availabe. Software is expensive, and I have my
                  service bureau do it. It's not used for offset prepress work however, so
                  finding a provider can be a little challenging.

                  Best,

                  Marnie

                  To: <PPLetterpress@yahoogroups.com>
                  From: Katie Harper <knharper@...>
                  Date sent: Wed, 09 Jan 2002 14:54:12 -0500
                  Subject: Re: [PPLetterpress] Re: another possible factor in exposing plates
                  Send reply to: PPLetterpress@yahoogroups.com

                  [ Double-click this line for list subscription options ]






                  > From: "Marnie Powers" <mpowers@...>
                  > Organization: Marriott Library
                  > Reply-To: PPLetterpress@yahoogroups.com
                  > Date: Wed, 9 Jan 2002 11:29:26 -0700
                  > To: PPLetterpress@yahoogroups.com
                  > Cc: vhindley@...
                  > Subject: [PPLetterpress] Re: another possible factor in exposing plates
                  >
                  > I have the image output
                  > on imagesetting film with a stochastic screen at "80". The difficutly is
                  > that the stochastic screen (as I understand it anyway) does not directly
                  > translate to lpi.


                  I'm unfamiliar with the term "stochastic" screen. Can you explain what this
                  is? Thanks.

                  Katie Harper




                  To post a message to the membership, send an email to
                  PPLetterpress@yahoogroups.com

                  To log on to the groupsite (confirmed Yahoo ID required), go to
                  http://groups.yahoogroups.com/group/PPLetterpress
                  [copious reference sources can be found onsite in Bookmarks (URLs),
                  Database (tables), Files (documents), and Messages (archives)]

                  Encountering problems? send an email to
                  PPLetterpress-owner@yahoogroups.com

                  To unsubscribe, send an email to
                  PPLetterpress-unsubscribe@yahoogroups.com



                  Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


                  Marnie Powers-Torrey
                  Studio Manager
                  Book Arts Program
                  J.Willard Marriott Library
                  (801)585-9191
                • bielerpr
                  ... Dear Marnie Have you tried ISIS Icefields (grayscale software, renders stochastic, available as a plug-in for Photoshop)? Heard great things, especially
                  Message 8 of 11 , Jan 9, 2002
                  View Source
                  • 0 Attachment
                    Marnie Powers wrote:

                    > I'm willing to explain the stochastic screen to the best of my ability.
                    > As I understand it, it is not a random screen. Under a loupe it looks
                    > very similar to the grain of photographic film and paper. The screen
                    > applies a spattered pattern to the image, the dots occurring more
                    > frequently in dark areas than in the light areas. In terms of fooling the
                    > eye into thinking it's seeing grayscale, stochastic is the most effective
                    > screen currently availabe. Software is expensive, and I have my
                    > service bureau do it. It's not used for offset prepress work however, so
                    > finding a provider can be a little challenging.

                    Dear Marnie

                    Have you tried ISIS Icefields (grayscale software, renders
                    stochastic, available as a plug-in for Photoshop)? Heard great
                    things, especially for inkjet.

                    http://www.isisimaging.com


                    Gerald
                  • Mark Attwood
                    Marnie, It was a few years ago that I did the research into the different wavelengths, and it seems I haven t filed it. The suppliers of the plates will be
                    Message 9 of 11 , Jan 10, 2002
                    View Source
                    • 0 Attachment
                      Marnie,

                      It was a few years ago that I did the research into the different
                      wavelengths, and it seems I haven't filed it. The suppliers of the plates
                      will be able to tell you the best wavelength to expose their plates, and the
                      suppliers of the bulbs will give you detailed info on the output wavelength
                      of the lamp. If I remember correctly there was only a small overlap at one
                      end of the spectrum, and this is why the metal halide will work, but only
                      with such a long exposure.

                      let me know what you find out,

                      Regards,
                      Mark.


                      Mark Attwood

                      The Artists' Press
                      Box 623
                      Newtown
                      2113
                      South Africa

                      Tel. +27 11 836 5474
                      fax. +27 11 836 6858
                      mark@...


                      ----------
                      >From: "Marnie Powers" <mpowers@...>
                      >To: PPLetterpress@yahoogroups.com
                      >Subject: [PPLetterpress] another possible factor in exposing plates
                      >Date: Wed, Jan 9, 2002, 5:56 pm
                      >

                      > Mark,
                      >
                      > Thanks much for the information. Do you have any details on the
                      > specific UV frequency of metal halide verses flourescent, and the ideal
                      > frequency for exposing photopolymer plates? If so, I'd be interested in
                      > seeing it.
                      >
                      > Best,
                      >
                      > Marnie
                      > Marnie Powers-Torrey
                      > Studio Manager
                      > Book Arts Program
                      > J.Willard Marriott Library
                      > (801)585-9191
                      >
                      >
                      > To post a message to the membership, send an email to
                      > PPLetterpress@yahoogroups.com
                      >
                      > To log on to the groupsite (confirmed Yahoo ID required), go to
                      > http://groups.yahoogroups.com/group/PPLetterpress
                      > [copious reference sources can be found onsite in Bookmarks (URLs),
                      > Database (tables), Files (documents), and Messages (archives)]
                      >
                      > Encountering problems? send an email to
                      > PPLetterpress-owner@yahoogroups.com
                      >
                      > To unsubscribe, send an email to
                      > PPLetterpress-unsubscribe@yahoogroups.com
                      >
                      >
                      >
                      > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                      >
                    • Marnie Powers
                      Gerald I m so glad that I joined this list. I ve learned so much already! Your referrals have been extraordinarilly helpful, and the discussion is to the point
                      Message 10 of 11 , Jan 11, 2002
                      View Source
                      • 0 Attachment
                        Gerald

                        I'm so glad that I joined this list. I've learned so much already! Your
                        referrals have been extraordinarilly helpful, and the discussion is to
                        the point and interesting.

                        Best,
                        Marnie

                        To: PPLetterpress@yahoogroups.com
                        From: "bielerpr" <bieler@...>
                        Date sent: Wed, 09 Jan 2002 23:22:58 -0000
                        Subject: [PPLetterpress] Re: another possible factor in exposing plates
                        Send reply to: PPLetterpress@yahoogroups.com

                        [ Double-click this line for list subscription options ]

                        Marnie Powers wrote:

                        > I'm willing to explain the stochastic screen to the best of my ability.
                        > As I understand it, it is not a random screen. Under a loupe it looks
                        > very similar to the grain of photographic film and paper. The screen
                        > applies a spattered pattern to the image, the dots occurring more
                        > frequently in dark areas than in the light areas. In terms of fooling the
                        > eye into thinking it's seeing grayscale, stochastic is the most effective
                        > screen currently availabe. Software is expensive, and I have my
                        > service bureau do it. It's not used for offset prepress work however, so
                        > finding a provider can be a little challenging.

                        Dear Marnie

                        Have you tried ISIS Icefields (grayscale software, renders
                        stochastic, available as a plug-in for Photoshop)? Heard great
                        things, especially for inkjet.

                        http://www.isisimaging.com


                        Gerald





                        To post a message to the membership, send an email to
                        PPLetterpress@yahoogroups.com

                        To log on to the groupsite (confirmed Yahoo ID required), go to
                        http://groups.yahoogroups.com/group/PPLetterpress
                        [copious reference sources can be found onsite in Bookmarks (URLs),
                        Database (tables), Files (documents), and Messages (archives)]

                        Encountering problems? send an email to
                        PPLetterpress-owner@yahoogroups.com

                        To unsubscribe, send an email to
                        PPLetterpress-unsubscribe@yahoogroups.com



                        Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


                        Marnie Powers-Torrey
                        Studio Manager
                        Book Arts Program
                        J.Willard Marriott Library
                        (801)585-9191
                      Your message has been successfully submitted and would be delivered to recipients shortly.