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13724Re: [PPLetterpress] polymer versus lead type

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  • kringds
    Feb 2, 2014
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      Eric,


      What are ornamental bearers? Over the years, in my quest for perfect inking on my C&P, I have gotten the recommendation of bearers from some. Others say as you do that they do not do much for roller height.
      In the past I did some test using strips of polymer as makeshift bearers and did not see any beneficial results. I think this is because of the softness of the rollers. For a bearer to lift and carry the rollers then they have to be pretty heavy on the bearer. If the bearer is type high then they would be hitting the form to the same degree.

      However, if I had adjustable bearers that could be increased incrementally above type high, possibly with tape, then I should be able to adjust them to a working height.

      I am sure this sounds idiotic to many, especially people that have presses that are finer than C&P NS. But to me it sounds like it would be worth a shot. My remaining question is if I need some type of texture (or ornament) on the bearers to keep the rollers from slipping. If that is the case then I would need to adjust them from the back which would be more trouble, obviously.



      ---In PPLetterpress@yahoogroups.com, <Megalonyx@...> wrote:

      Roller bearers don't do much in regard to roller HEIGHT setting. They can have a real effect on roller motion, which is a serious problem with photopolymer, magnified by differences in roller and truck diameter on a platen, causing slur. But they don't do much at all to lift soft rollers. When used on a proof press with automatic inking, I think the effect of bearers is more to equalize impression, which is why it was standard practice when pulling repro proofs. The reason Kelsey sold so many sets of wide roller bearers is because they had one style of roller truck that was not keyed to the shaft and just turned loosely: crazy slur.

      When I started printing it was just metal type and plates and the odd linoleum cut, all easily inked using my Dad's and my teacher's method, which was to inspect the image left on the roller after it passes the form, look at the print, and then adjust the Morgan truck accordingly. This did not work when I added photopolymer plates to the process, in large part because the harder contact wanted by a metal form was too much for photopolymer and the over expansion of Morgans in compensation lead to eccentricity, which causes the wandering ink densities that have been questioned so often online. Eventually I realized it was a more complicated relationship between roller and plate surface, and truck and track, because the photopolymer plate does not grab the roller as a metal form does, it slips; some pre-photopolymer authors tell you to keep the trucks smaller than the roller so the form will grab the roller and make it turn. Do that with photopolymer and all you will get is ghosting, slurred leading and trailing edges and ink wiped onto the edge of the plate. With very hard rollers I found that using ornamental bearers grabbed the roller and got it turning at speed before it hit the form: with photopolymer the rollers must roll over the entire form at even speed, no slippage anywhere. That's easier on a Vandercook with geared form rollers than it is on most platens.

      Eric Holub, SF



      ---In PPLetterpress@yahoogroups.com, <kwhalen.incline@...> wrote:

      Re: [PPLetterpress] polymer versus lead type Type high bearers pretty much take care of this.

      You’ll figure out yourself how fussy you are happy with being, as soon as you gain experience with the printed images.


      Graham Moss
      Incline Press
      36 Bow Street
      Oldham OL1 1SJ  England

      http://www.inclinepress.com
      news blog: http://www.inclinepress.wordpress.com



      I have read many times that with polymer plates you have to be much more precise in the setting of the roller heights (on a platen press at least) than with lead type. Why is this so? Is it because the edges of the letterforms are sharper on lead, so that you can hit them with the rollers a little harder without showing any slur? Or does it have to do with the material? Does the ink transfer easier to lead than to polymer?
      thank you,
      bryan kring










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