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9478Re: platemaking issues

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  • Gerald Lange
    Mar 7, 2008
      Cody

      I went back a ways to find this but your original post indicated you
      are using Jet 152s. If these are polyester-backed Boxcar supplied
      (KF152) I think they are Toyobo brand, not Jet. I'm probably wrong but
      as far as I can tell Jet doesn't make a plate in this configuration.

      There has been problems with this particular configuration as reported
      a number of times both here and on the Briar Discussion list.

      I think you may be more successful by trying a different plate in your
      testing.

      In response to my questioning Harold Kyle did admit in a previous post
      that he is using a custom technique for processing these plates. I'm
      assuming you would need to know that information yourself in order to
      process the plates correctly. Or all of your trials are to no avail.

      Gerald
      http://BielerPress.blogspot.com

      --- In PPLetterpress@yahoogroups.com, Cody L <itsfancyletterpress@...>
      wrote:
      >
      > First of all thanks for the information and your
      > personal tests of the polymer and what it is doing for
      > you. I did not think to stop the washout before you
      > get to the clear base. I was just trying to match the
      > materials purchased from Boxcar on previous plate
      > orders.
      >
      > I also appreciate the quick run down on light and
      > plate interaction. Yes the book in question is on its
      > way from a friend but it is not here now. I thank you
      > all for your patience!
      >
      > With a hand washout i will probably have to be careful
      > with uniformity of the depth washed out and make sure
      > they properly dry before the hardening process.
      >
      > If I were to create my own conversion to florescent UV
      > bulbs what should I look for. I have never searched
      > for the bulbs before just the entire platemaker. I
      > don't see that it would be very difficult to
      > accomplish a custom box that could sit on top of my
      > vacuum unit and have it hooked to a darkroom timer. I
      > have found bulbs online but I do not know if a UVA
      > tanning style bulg is what is required or a UV black
      > light bulb would be the correct style.
      >
      > Thanks!
      >
      > cody
      >
      >
      > --- Peter Fraterdeus <peterf@...> wrote:
      >
      > > Hi Cody, et alia
      > >
      > > Richard wrote:
      > >
      > > > The characteristic
      > > > slope of a well made photopolymer plate is the
      > > result of how
      > > > photopolymer bends the light ray at the point it
      > > enters the
      > > > photopolymer.
      > >
      > >
      > > Photons do travel in a straight line, and thus a
      > > broad light source
      > > will create a light cone, regardless of diffraction.
      > > Your argument implies that the source is an
      > > infinitely distant point.
      > > While the ray may bend due to the change in medium,
      > > I don't think
      > > that's the reason for the slope of the shoulder.
      > >
      > > As far as it goes, I am finding that the plate
      > > material from Boxcar
      > > produces very vertical shoulders. I think this is as
      > > much due to the
      > > fact that the yellow color absorbs the UV, and
      > > therefore the photons
      > > coming at an angle do not spread much beyond the
      > > point of entry. Those
      > > which enter at a shallow angle are absorbed before
      > > reaching the base.
      > >
      > > It seems to me that the shoulder angle is related to
      > > the photo-
      > > sensitivity of the polymer.
      > > I've been trying to find more in-depth technical
      > > info on all this,
      > > rather than apocryphal say-so, but the
      > > manufacturer's documentation
      > > (what little there is) seems to have been translated
      > > from Japanese
      > > into English leaving much to the imagination.
      > > Perhaps I'm looking up
      > > the wrong trees. Google likewise provides little
      > > elucidation. Of
      > > course there's Gerald's book, but why not reinvent
      > > the wheel every
      > > generation? Also, the plate materials seem to have
      > > changed since the
      > > copy I have was published.
      > >
      > > The problems I was having previously with loss of
      > > points and moving on
      > > the base had to do with too long wash-out, which
      > > would undermine the
      > > exposed points.
      > >
      > > I'm now using about 3.5 minute wash instead of five,
      > > which has done
      > > wonders for the stability of the fine points and
      > > rules. With the 'deep-
      > > relief' base it needs another minute or so to clean
      > > the base, but I'm
      > > washing as short a time as possible.
      > >
      > > Leaders and isolated dots and periods are solid
      > > cylinders. Not much
      > > shoulder, but they're hard as rocks, firmly seated
      > > on the base and
      > > seem to be printing fine. In fact, the older plate
      > > material I was
      > > using produced a wide shallow shoulder, the current
      > > stuff, with the
      > > clear untinted plastic base produces a nearly
      > > vertical shoulder.
      > >
      > > YMMV, of course....
      > >
      > > Peter Fraterdeus
      > > http://ExquisiteLetterpress.com
      > > http://dubuquebookarts.com
      > >
      > >
      > >
      > >
      > >
      > > On 7 Mar 2008, at 10:07 AM, richard seibert wrote:
      > >
      > > > All light, even after being diffused, travels in a
      > > straight line.
      > > > When light travels out of one substance into
      > > another, its speed
      > > > changes. This changes the angle at which the ray
      > > travels. Think of a
      > > > pencil in a glass of water. Every substance has an
      > > "index of
      > > > refraction" which determines what this angel is.
      > > The characteristic
      > > > slope of a well made photopolymer plate is the
      > > result of how
      > > > photopolymer bends the light ray at the point it
      > > enters the
      > > > photopolymer. This is also why film needs to be
      > > emulsion down.
      > > > Nothing that happens to the light in-between being
      > > emitted by the
      > > > electrons in the lamp and entering the film will
      > > effect what happens
      > > > at the boundary between film and polymer. (Unless
      > > the intervening
      > > > substance absorbs or reflects the necessary
      > > frequencies.)
      > > >
      > > > Too steep an angle is the result of not enough
      > > photons (or not enough
      > > > photons of the right frequency) to fully
      > > polymerize the material.
      > > >
      > >
      > >
      > >
      >
      >
      >
      >
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