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  • #459278
    blackandwhite
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        I have recently started printmaking with photopolymer intaglio plates and I’m having challenges with too much plate tone. I’m using Toyobo KF95 plates and Charbonnel Aqua Wash black inks. With all inks and wiping techniques I get quite dark plate tone. If I wipe the plate so much that the plate tone is gone, then all the ink from the lines will be gone too. I’m using newspaper paper for wiping. Final wiping with palm of the hand didn’t help. Charbonnel carbon black ink was the worst (darkest plate tone) and their RSR ink was the best (least plate tone), but the difference is small.

        Do you have any tips that how the wiping should be done to get rid of the dark tone?

        With normal copper plates I can get clean white print without problems, but it seems that the ink sticks to the photopolymer plates like a glue… I attach one example where there should be ink only in the lines, so all the plate tone is unintentional and I’d like to get rid of it. (The picture is from a technical pen croquis drawing that just happened to have nice lines for testing the process.)

        #661502
        bridog
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            I found this same problem and realized there were a range of factors contributing to the plate tone.

            First, the polymer plate by it’s nature has a microscopic pitted surface in the polymer. So even minute amounts of ink will be trapped in the surface texture. This makes it a bit more challenging to get perfectly white areas of paper. But it isn’t impossible.

            That being said I also find that wiping of the plate plays a role.
            I have been using a less stiff synthetic fabric for wiping in lieu of traditional tartalan. It is a web interface that I source from a local fabric shop. I find once it gets a build up of ink residue in the material it picks up ink even better. I follow up by wiping the plate using the flat palm of my hand and a piecee of yellow pages newsprint from an old phone book. If you don’t have this plain absorbent newsprint will work and so will a non-coated camera lens wiping tissue.

            Then for areas I want to remove as much ink as possible that will print as white I use moistened cotton swabs or the damp end of an old cotton t-shirt (stretched over a finger) to remove ink from these locations. I generally print with a modified oil ink like Caligo or Akua and water moistened cotton. This seems to work well and leaves pretty clean areas of white where I don’t really want plate tone.
            If you are using traditional oil ink I am sure a bit of vegetable oil or rubbing alcohol instead of water might produce the same results.

            Finally one other factor to consider would be the dampness of your print paper. Make sure it isn’t too moist (blot it well) as extra moisture in the paper contributes to pick up of unwanted plate tone.
            Hope this helps.

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            #661503
            blackandwhite
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                Thanks for the tips! I did new experiments and got slightly better results, but I’m still having problems with ink coming out of the ‘etched’ lines. Might be that I have to tune the plate exposure process so that I get deeper lines on the plate that will hold ink despite of heavy wiping.

                I also tested some new inks. Seems that the pigment type has big impact on plate tone. I tried Charbonnel Soft Black ink that contains only ivory black pigment, which is quite coarse grained and is relatively weak pigment, and it gave the best results so far. The plate tone is almost acceptable when doing normal wiping with newsprint.

                I also tested polishing the finished plate with #1000 grit sandpaper, but that ruined the plate. The material just below the plate surface appears to be very sticky and holds ink like crazy, so there is probably no way to make the plate surface smoother.

                #661504
                blackandwhite
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                    Update on the progress: Seems that the root cause has been found and it took about dozen attempts to make a working plate.

                    Originally I had problem that wiping away the plate tone took also the ink from the lines. Turns out that the lines were exposed too shallow, i.e. heavy wiping did lift all ink from the plate because the lines just weren’t deep enough to hold the ink. The lines were shallow because my positive masks were printed with laser printer that doesn’t produce opaque enough black that would allow me to do double exposure (aquatint screen + artwork). It looks that it is common problem with laser printed positives. When I exposed both aquatint screen and the artwork, the fine lines became too shallow on the plate with all exposure time combinations. When I left out the aquatint screen, the wide lines became too deep but the fine lines were perfect.

                    The solution was that I wrote a software that applies aquatint screen only to the ‘large’ black areas of the image, so those won’t etch too deep on the plate, but the fine lines are untouched (no aquatint screen) so those expose perfectly on the plate. That allows me to use normal laser printer to print the positives and I can do heavy wiping on the plate to remove excessive plate tone.

                    I attach here closeup of the original mask image and the processed one (on the right). Here the aquatint screen is setup for 300 dpi printing, which is the maximum that works with my 600 dpi laser printer.

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