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Re: Making Negative for Photopolymer Plates

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  • Eric
    ... Is this because only some of the exposure is through the negative, and the rest through the back of the liquid? Or does the liquid have a different
    Message 1 of 11 , Feb 25, 2011
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      --- In PPLetterpress@yahoogroups.com, "Rod" <granthams@...> wrote:
      >

      > Sheet photopolymers are more light sensitive and have a such short exposure latitude that using negatives produced on a laser printer don't have enough density. However, we have excellent results with liquid photopolymers using negatives made a laser printer. We imprint wooden tokens on a C&P with dies made with liquid photopolymer.
      >

      Is this because only some of the exposure is through the negative, and the rest through the back of the liquid? Or does the liquid have a different exposure latitude?
      What is your experience with shelf-life, both raw liquid and processed material? I have a processed sample of Merigraph liquid photopolymer that is still supple and it is over twenty years old (but never exposed to ink or solvent).
      Eric Holub, SF
    • John Risseeuw
      I talked to a guy at Freestyle Photo in L.A. today and he said that orthochromatic film is no longer being made and they have none to sell. Konica had been
      Message 2 of 11 , Feb 25, 2011
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        I talked to a guy at Freestyle Photo in L.A. today and he said that
        orthochromatic film is no longer being made and they have none to sell.
        Konica had been making it and Freestyle sold it under the Arista label. It's
        gone. I have taught a photo processes course here at Arizona State
        University for 30 years, making films in a process camera darkroom for photo
        printmaking, and I can no longer teach it. We do make photopolymer plates
        using other methods, but it was always good to fall back on dense, crisp
        darkroom films.

        The lack of availability of ortho film may soon impinge on service bureaus
        with Imagesetters, although there is a company still making film for them,
        apparently. I hope someone soon comes up with a better process for digitally
        printed films that are opaque and sharp.

        John


        On 2/25/11 12:20 PM, "Rod" <granthams@...> wrote:

        >
        > Have you folks looked in to producing your own negatives? Twelve years ago
        > when we switched to digital plates, we couldn't give away our
        > NuArc process camera and flip top platemaker. We junked it just to get more
        > space in our shop.
        >
        > Talk to a few local print shops and you may score a camera for little or
        > nothing. Both rapid access and lith film are available from
        > <http://www.valleylitho.com/acatalog/Valley_Litho_Supply_Film_5.html> , a
        > source we have had excellent results with.
        >
        > Sheet photopolymers are more light sensitive and have a such short exposure
        > latitude that using negatives produced on a laser printer don't have enough
        > density. However, we have excellent results with liquid photopolymers using
        > negatives made a laser printer. We imprint wooden tokens on a C&P with dies
        > made with liquid photopolymer.
        >
        > <http://www.youtube.com/watch?v=MvOKy3Msa4I> is one of my casting videos on
        > YouTube that shows another use for liquid photopolymer.
        >
        > Have fun!
        >
        > Rod
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
        >
        >
        >
      • Rod
        ... Liquid photopolymer has a much greater exposure latitude. As a trial we left some on a shelf for about 5 years and noticed that exposure times had to be
        Message 3 of 11 , Feb 25, 2011
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          > > Sheet photopolymers are more light sensitive and have a such short exposure latitude that using negatives produced on a laser printer don't have enough density. However, we have excellent results with liquid photopolymers using negatives made a laser printer. We imprint wooden tokens on a C&P with dies made with liquid photopolymer.
          > >
          >
          > Is this because only some of the exposure is through the negative, and the rest through the back of the liquid? Or does the liquid have a different exposure latitude?
          > What is your experience with shelf-life, both raw liquid and processed material? I have a processed sample of Merigraph liquid photopolymer that is still supple and it is over twenty years old (but never exposed to ink or solvent).
          > Eric Holub, SF
          >
          Liquid photopolymer has a much greater exposure latitude. As a trial we left some on a shelf for about 5 years and noticed that exposure times had to be increased from 1 minute to 1 minute 45 seconds through the base on the older material. Our normal exposure time using F20T12BLB fluorscent bulbs is 1 minute base, 2 minutes through the negative with a 5 minute in-water post exposure. Our lights are about 3 inches away from the negative.

          The finished die tends to yellow with age, but doesn't seem to deteriorate. We've been using both sheet and liquid photopolymers since 1982. Both the total thickness and relief depth are easily controlled with liquid photopolymers.

          Since the printing plates we need in my print shop are usually less than 10 square inches, scrub out is done in the sink. Liquid photopolymer scrubs out in less than a minute, compared to about 5 minutes for sheet photopolymer which we seldom use. Hard liquid (95 durometer) works as well for making stamp matrix as metal backed hard sheet.

          In no way am I discouraging the use of hard sheet photopolymer, but in our applications the liquid is more practical.

          Rod
        • Jan Kellett
          Thanks, Veronica, part of the problem is customs so I wanted to get somewhere in Canada. I think I ve found a bureau not too far from where I live, so can cut
          Message 4 of 11 , Feb 26, 2011
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            Thanks, Veronica, part of the problem is customs so I wanted to get somewhere in Canada. I think I've found a bureau not too far from where I live, so can cut out the middle men (customs, USP and Canada Post), at least for the negatives. I think for me making the negatives is a bridge too far, certainly at the moment. I print, illustrate and bind too, and the processes are taking over the mad-house :-)
            Jan
          • Yvon
            Jan, there are at least 4 service providers in Vancouver alone that run film every week, if not everyday. Feel free to contact me for more info. I can also
            Message 5 of 11 , Feb 27, 2011
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              Jan, there are at least 4 service providers in Vancouver alone that run film every week, if not everyday. Feel free to contact me for more info. I can also give you the name of a graphic supplier on the Island that might know someone even closer to you.
              Regards, Yvon

              --- In PPLetterpress@yahoogroups.com, Jan Kellett <jan.kellett@...> wrote:
              >
              > Thanks, Veronica, part of the problem is customs so I wanted to get somewhere in Canada. I think I've found a bureau not too far from where I live, so can cut out the middle men (customs, USP and Canada Post), at least for the negatives. I think for me making the negatives is a bridge too far, certainly at the moment. I print, illustrate and bind too, and the processes are taking over the mad-house :-)
              > Jan
              >
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