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  1. #1
    Thornysarus's Avatar

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    Default Burning/Washout problems

    Long-time lurker, first post, be gentle. Andymac sent me. Apologies in advance for the lengthy post:

    I'm having problems with peeling emulsion during washout. I'm using QTX and I'm sure it's still good. I degrease and abrade properly so I'm sure the problem is in exposure and/or washout:

    My burn rig: 500 watt halogen (new fixture with no glass) 24 inches above screen. Laser vellum positives sandwiched between tempered glass and 1/2-inch black gator foamboard inside and elevating the screen off the table.

    Screens: 155 white mesh, coated 1/1 and dried overnight, stencil-down in complete darkness.

    I just burned 3 screens: 10, 12 and 14 minutes. All of them unacceptable. All were an easy washout, but they all started peeling during washout to some degree. The 10 minute screen peeled like a bitch, mainly around the outer edges of the positive. The 12 minute screen similar, but not so much and mainly around the edges, and the 14 minute peeled the less of them all.

    I was under the assumption that peeling was due to overexposure. Is there any other factors that could cause this? Should I expose longer?

    Also, I've read that halogen doesn't put off proper amounts of UV. Should I switch to another light source and if-so, what would you all recommend?

    Vellums are easiest for me to use since most of my work is large format, fine art (think huge, Warholesque sort of stuff on handmade paper). Should I switch to transparencies, and if so, can anyone recommend an economical solution for transparency seps like up to 3x5 feet?

    I want to get this process tweaked so I can start slinging ink again.

    Much appreciation in advance, and Andy, I still owe you that beer.

    Thorny

  2. #2

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    Default

    try to coat only the reverse (non squeegee) side of the screen. that will reduce your exposure time a bit, and make your image sharper. at 155 mesh, you don't even need to coat on each side, the mesh is so coarse-- it's possible that you leave deposits of emulsion that are too heavy, hence the peeling. Also it's possible that your drying room isn't dry enough-- high humidity causes bad exposure a peeling at the washout, maybe get a de-humidifier going. Also, the longer your emulsion dries, the better results you get... try drying you coated screens at least 1 hour before exposure, with a strong fan pointed at it.

    we used to have this set-up before: 30x40 screens, 175, 200 or 230 mesh, coated 1/1, 2 150 watt incandescent lights in a big aluminium pie plate, 18 inches from the bottom of the bulb to the surface of the mesh, positive weighted down by a 3/8 inch plexi and paint cans in the corners for extra wieght. 25 minutes exposure.

  3. #3
    Premium Member
    Andymac's Avatar

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    Default

    longer exposure.

    try a step wedge test on one screen, the same coating one and one - make sure it is nice and even and dry - and the same vellum material you were using, and start the first exposure strip, and pull the black paper/ruby/whatever one step every 2 minutes.

    If you do 7 steps, once you pull the paper away for the last, let it go another 14 minutes. That will give you washout times of 16, 18, 20, 22, 24, 26, 28

    Figure out which is best, let us know the results.


    if you have a scrap or rubylith or dense black paper, put that under your screen on the first step, but not where your positive film is.


    better lamp? 1000w metal halide grow lamp - but lots use the halogen

    if stencil is peeling, you need to burn longer to harden it. if it goes on real thick, it never burns through properly and will peel.

    once you get it to work, play with positive materials. you don't say if you are trying to print out the film - a cheap big film is available from blueprint shops, frosted mylar or vellum, don't know what they call it. that will burn positives and is cheaper than film.


    who be thorny? beer? OK!
    Andymac

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

    Todo es empezar.

  4. #4
    Thornysarus's Avatar

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    Default

    Andy, I'll refresh your memory. I'm Terry Thornhill in Nashville. We've exchanged a few emails about screenprinting, I offered to mail you a six-pack of Yazoo (A local microbrew) and you hesitated... Something about the legality of mailing beer to Canada...

    I'm reclaiming the aforementioned screens and recoating today. I'll try the step wedge test and report back.

    I'm actually having my seps run at a local screen printer's shop. He's a friend and I trade out design work for using his stuff. He can output 11x17 laser vellums and I tile them together on the light table back at the studio. I do have a laser printer in-house, but can only output up to Legal size.

    Exposure Lights: I had some second-hand metal halides, but sold them b/c I was offered twice what I paid for them and I needed the money at the time. Turns out the guy that sold them to me told his cop buddy that he suspected I was growing pot and I had "concocted some story about using them for printing" which resulted in giving the local fuzz a tour of my studio and a crash course in screen printing. Thus, the move to halogen. Is there a primer somewhere about building your own metal halide rig? The ones I see online are big, bulky and pricey as hell, and I like my "Hanging above the table" light rig. Would be happy to convert to Metal Halide if I could simply switch out the source.

    Thanks for the responses and the help.

    Thorny
    Last edited by Thornysarus; 08-21-2008 at 07:48 AM.

  5. #5
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    Nicholas Wilson's Avatar

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    i love yazoo.... still have my empty growler, use it as a water jug in my fridge.
    The Half and Half
    Now Selling Speedball Ink for all your East Coasters.

  6. #6
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    ImJustRickG's Avatar


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    Yeah... how are you coating those screens? How big are they?

    I quit using halogens; too unpredictable and I swear they were losing UV. My burn times got longer and longer...

    How are you washing out?

    FWIW: This is the crappiest part of screenprinting. Unil you get to the next step. Hang in there!
    Shizouka!

    Brg!

    "I don't know shit about screenprinting and can still tell all the questions you ask are retarded." -Blonde
    I can't imagine being in this position and saying to myself "Hey! I bet the people at Gigposters will be helpful!". -Phoon

  7. #7
    squeegeethree's Avatar

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    Default

    Quote Originally Posted by Thornysarus View Post
    Exposure Lights: I had some second-hand metal halides, but sold them b/c I was offered twice what I paid for them and I needed the money at the time. Turns out the guy that sold them to me told his cop buddy that he suspected I was growing pot and I had "concocted some story about using them for printing" which resulted in giving the local fuzz a tour of my studio and a crash course in screen printing
    "You see these plants are important to my process mazn. They help breakdown the VOCs and I make hemp shop rags."

  8. #8
    andydiesel's Avatar

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    i'd say give it a try at 20 minutes. when our regular exposure lamp is out and we have to use out back up 1000w grow light we have to burn a 195 yellow mesh for 20 minutes or so for the emulsion to fully burn.

  9. #9
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    adrenochrome's Avatar

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    I had the same problems with QTX. That stuff is thick!

  10. #10
    Premium Member
    Andymac's Avatar

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    I have a 1000w metal halide hanging over the exposure unit. 5-7 minutes on yellow mesh,its about 4 feet above.

    they have their own transformer and ballast, and socket, you can't just add a bulb to an existing recepticle. My MH unit came from the local hydroponics shop.

    And yeah, I had the cops in one day, same deal - they said 'that's a first'. But here's the thing, maybe if you ask the local cops, they will give you a lamp from their next bust?

    good luck Terry. Once you nail it, you should be getting consistant screens. Just keep playing. and thanks for the beer offer. I have Shaftsbury 420 beer in the fridge right now. It's a different culture up here - you can't ship it across the border or with the post office, but you can name a brand in order to attract the smokers. Its actually great beer. goes well with pot, too!
    Andymac

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

    Todo es empezar.

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