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  1. #1
    SplitEar's Avatar

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    Default Printing a photo (VERY fine halftones)

    Hi!

    I'm about to embark on attempting to screen print a photo.
    Starting simple, single colour (Black & white photo, with the substrate being the white, black being the ink)

    I have just upgraded all my equipment, currently running a Lumitron vacuum exposure unit and using Permaset Aqua water based inks.

    Registration isn't an issue, it's mainly making the screen i'm thinking of.

    I was hoping i could get some tips?

    So far, i get my image, greyscale it then bitmap it AFTER i've made it acetate (film) size, this leaves me with incredibly fine halftones (1x1px), i've adjusted the dot per line number to try and make it more manageable, but to get as close to photo realism, i'm doing it at 100 dots per line, 300dpi on an A2 document (7000px tall)

    I'm using a 71t screen (BRITISH numbers)

    I am wondering if there is anything i need to consider more?
    If anyone has any tips for this to go more successfully than i am anticipating?

    I can provide the image, bitmapped if anyone would like.

    Thank you.
    -Alex

  2. #2
    Premium Member
    Andymac's Avatar

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    Default

    71t is 180 weaves per inch?

    100 lpi halftone won't probably expose. a 25-35 lpi halftone, maybe 45 on that mesh

    If you want to try for 100lpi halftone, I would switch to 380 or better 420 weave mesh (165t?), use a proper process ink, quite possibly switch to UV ink if you really want to do it.

    there's a whole bunch of other shit that goes along with printing extra fine halftones in screenprinting.

    I would get a lot of beer before you start printing, you will need it.
    Andymac

    services www.squeegeeville.com
    equipment www.tmiscreenprinting.com

    Todo es empezar.

  3. #3
    SplitEar's Avatar

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    Default

    Yeah, 71T is 180 threads/inch at medium thickness (Over here we only seem to have small, medium and heavy thicknesses)

    I can lower the lpi easily, i was just experimenting really, the image still survives detail at around 45 lpi, anything lower than the image just turns into a black mess really.

    I can get process black from my supplier, was just wondering what the difference is between process black and standard black? I use permaset inks: http://www.permaset.com.au/

    Any other suggestions? Such as squeegee technique? Currently using a red d-blade, think that should be ok, it's soft as.

    To be fair, my main worries are literally the exposure of my screen, i use an ok emulsion, but i imagine getting one with better bridging would really help me.

    and yes, beer and lots of music. If successful, i will be very happy..haha.

  4. #4
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    Andymac's Avatar

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    Default

    true process inks are more transparent than most, and they usually are formulated with a lot of retarder and the ability to 'stand up' when printed, with nice sharp sides - if you have a nice sharp stencil edge forming the dot, and have a nice sharp film positive forming the image on the film.

    your blade needs to be sharp and nick free.

    If you are printing on paper, a higher mesh screen gives you a nicer looking dot, (and a sharper image) and the ability to hold the detail on the stencil.

    If you are screwing around with B&W photos and want a nice smooth look, try printing a duo or tri-tone (3 shades of grey) It can give you a nicer tonal range than trying to capture the whole gamut from light to dark in one layer.
    Andymac

    services www.squeegeeville.com
    equipment www.tmiscreenprinting.com

    Todo es empezar.

  5. #5

    Default

    Relatively higher mesh counts to what you have here, as well as thinner coats of emulsion, and some very opaque films (actually, if you can order an imagesetter film, that's best because even the lights will be super opaque) will all help you make a better screen.

    When it comes to the actual printing, a viscous ink that dries slowly is the best formulation- especially since if you're printing by hand and running slow at all, a thick flood will help keep the lighter grays (with isolated, small dots) open longer and allow them to continue to transfer ink/not fill in, while still promoting image fidelity in the reverses (thicker ink doesn't 'spread' as much hopefully). A screen lubricant/startup fluid will be a must.

    Printing on very smooth stock is helpful as well. Keep lots of newsprint you can burn through as well as a few sheets of acetate or mylar around; some lint free cloths to help wipe the screen out now and then with some of your startup fluid.

    You may wish to 'face' your stock first by running a pass of matt medium or white, especially if you're printing on soft cotton rag- this'll cut down on some of the pocking and such that can create issues as you're printing. If you start with a smoother and less absorbent surface it'll help in the long run and I have found the ink will lay better too in many cases.

    Hard duro, freshly sharpened or brand new squeegee is a must.

    Good luck.

  6. #6

    Default

    Also, if you're going to mess around with duotones/tritones, you better do some research into the screen angles. For a duotone, I've found 45 degree/70 degree to be a really good dot formation/rosette with both screenprint and offset. I'm not as sure about tritone.

  7. #7

    Default

    We've managed to hit 75 lpi consistently on 34 micron 380 mesh and simply could not get any higher consistently. We did manage to hit 85 a few times but that was mostly because we have favorable images to work with that did not have a lot of midtones in them.

    The finer the resolution though, the more likely moire will come into play so try to keep that in mind.

    Also for any finer work you'll want to switch to UV Ink because it's nearly 100% solids and not prone to environmental issues nearly as much as water based inks.

  8. #8
    squeegeethree's Avatar

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    100 lpi on 420 mesh is the highest I have gone. I got my best results with imageset films and indirect emulsion.

  9. #9

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    Quote Originally Posted by squeegeethree View Post
    100 lpi on 420 mesh is the highest I have gone. I got my best results with imageset films and indirect emulsion.
    Luther, do you have a local to NYC source for large format imageset film? Like, bigger than 20X38/22x40?

  10. #10
    squeegeethree's Avatar

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    That's hard to find these days. The 3 companies that I have used over the last 15 years have all gone out of business or stopped making large films. The remaining ones are tiny. But there is someplace that still does it because one of my clients brings in big films but she goes to a broker for these and he won't tell her where he gets them. I think the source is in the Hassidic community.

    Let me ask around some more.

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