Screenprinting Process and Guidelines

jump to:

Coating Screens ::: Exposing Screens

Rinsing Stencils Out ::: [flash curing stencils]

Inking ::: [mixing pavonine inks]

Printing ::: [printing setup] [printing workflow] [mylar registration]

Cleanup ::: [reusing stencils] [reclaiming]

 

Coating Screens

Supplies: degreased screens, scoop coater (free of nicks and dents), emulsion (SP 9500), ink spatula, 5 (at least) 2”x 2” squares of foam core

Coating screens is fairly straightforward. Don’t worry too much about mucking it up the first time because, if you put too much on, you can usually take the scoop coater and scrape off the excess.Before coating screens, label them by attaching a length of masking tape the outside of the frame and marking your initials with a sharpie.

  1. Open the emulsion. Gently stir it so as not to create any air bubbles, but enough to homogenize it.

  2. Pour approximately 1-2 cups of emulsion into scoop coater, again, taking care to minimize air bubbles. Put the lid back on the emulsion; it is light-sensitive.

  3. In the washout booth, prop a screen up in the notch closest to the back, so the screen is nearly vertical. Push the bottom edge of the screen back so it doesn’t slide when you are coating it.

  4. Hold the scoop coater as level as possible, with the thin lip closest to the screen and the thicker lip closest to you. Hold the scoop coater as far down on the screen as possible, and touch the thin lip to it uniformly. Tip the scoop coater forward, and as soon as you see that the emulsion touches the screen for the length of the coater, press into the screen gently and pull the coater up the length of the screen.

    There is a delicate balance between too much pressure and not enough. If your emulsion is very thick, you need to use a bit more pressure against the screen when you are pulling up. If you are using too much pressure, the screen might make a cracking sound, which could eventually lead to it breaking or loosening.

  5. After you have coated the front of your screen, turn the screen over and repeat the coating process.

  6. Using the squares of foam board as tools, gently scrape any extra emulsion until it reaches the edges of the screen. You probably won’t have enough emulsion on the screen to cover all of the edges, so you’ll need to dip into your scoop coater. Again, take care not to agitate the emulsion too much which will cause air bubbles. Toss the cards out when they become too sticky or unusable.

  7. Promptly place screen into light-safe cabinet, with the front of the frame facing down. Let them dry overnight for best results.

Exposing Screens

Supplies: Your dry screen, scotch or masking tape to secure film to screen (optional), your dry film, glass cleaner, lintless paper wipe

After your film and screens are completely dry (do NOT attempt to use them if they are not, it can get very messy and damage your film), clean the glass on the Amergraph by spraying a small amount of aerosol glass cleaner onto the glass bed and cleaning up with a paper wipe. Do not use any other chemical to clean the glass!

Turn on the Amergraph. Find a setting for 60 (SP9500 emuslion only) light units. If you need to, you can program one in.

In safelight conditions, open up the cabinet and prop your screen against a wall, with the flat side facing you. Please do this on the same wall that the door is on; there is a light leak under our door and it could potentially fog your screen.

Hold your film up to the back of the screen and note its orientation: it should be in reverse of what you hope to see on your paper. In other words, if you have text or symbols in your image, they should be backward in this view.

Using a small amount of tape (any tape you use will result in a stencil of the tape which ink could seep through when printing), secure the film to the approximate middle of the screen. To double check that you are going to get the correct result, hold the screen up, front facing you, and look at your film through the screen. From this view, it should be correctly oriented (i.e., the words/symbols will appear how you would like them to appear on your paper).

Place the screen very gently in the approximate middle of the glass; it scratches very easily and you don’t want your film to slip or twist out of position. With the screen in the center of the glass, close the Amergraph’s blanket top. Do not twist the knob that is secured with masking tape, as the pressure of the unit is currently set in a desirable range. Exit the room, as exposure to UV light can be hazardous to your health.

When the exposure is complete (the display will say EC and the noise will stop), gently remove the screen and film from the glass. Remove your film from your screen carefully, then carry your screen to the washout booth.

Rinsing Stencils OUT

When rinsing out the stencils, there are three things to remember: Use tepid or cold water, don’t use hot water, and make sure the water isn’t hot. It’s in your best interest to grab ear protection (there are two headphone-style sets available) for this step. The sound of water hitting the screen is quite loud.

  1. Turn on the backlight in the washout booth, as this will help you see your progress. Examine the hanging spray hose on the stainless steel sink (NOT the pressure washing gun). Make sure it isn’t set to hot by turning the left knob off and the right knob fully on. To be sure, just spray your hand for a few seconds.

  2. With headset and backlights on, begin spraying in small circles from left to right, starting in the upper left corner of the screen, even though there is no stencil there. You want to work your way down all the way to the bottom, and spray the entire screen. Rinsing out ALL unexposed emulsion will accelerate drying time.

  3. Repeat this process on the back, paying special attention this time to the stencil area. When using the SP9500 emulsion, t’s really very difficult to wash out parts of the stencil that are meant to stay, unless the water is hot or warm, so don’t fret too much about it.

  4. When you have rinsed the screen thoroughly, prop it up on the stainless steel counter behind you, and place a fan (on high) in front of it. Don’t close the door as you leave, as the air circulation will aid in quick drying time.


Flash Curing Screens

A flash cure can enhance the stencil’s integrity. After the stencil is fully dried, you can place it either on the Amergraph for 1-4 lu or set it out in the sun for a couple of minutes.

INKing

We have a few brands of ink that we use in screen printing. The most common is Pavonine, which has a buttery texture, and needs to be mixed.

Mixing Pavonine Inks

Supplies: yogurt container with lid, plastic fork, plastic spoon, ink spatula, gram scale

Pavonine Ink comes as a clear base with pigment additives. The ratio of pigment to base is anywhere from 2% to 6%, with 2% being a pastel-ish shade of the pigment and 6% being the most opaque. You measure the ink not by volume, but by weight. You can achieve this by the following method:

To see if the formula is truly giving me 3% pigment, I use this formula:

3.319 + 107.3 = 110.619(.03) = 3.319

After you have mixed your ink, label the container! If you are unsure of what concentrations you used, at least guess (ie "Approx 3% ruby red, 2% blueberry"). Please wipe down the ink mixing area with a towel. Ensure that there are no blobs of ink on the outside of containers, the scale, etc., wherever some unsuspecting colleague could mash their hand into it.

Safety Alert: please cross out any references to food on the yogurt container!

Printing

Printing Setup

I work left to right, using the following setup. I keep a couple of towels within reach.

 

Printing Workflow:

  1. Clamp the screen to the table using Jiffy Clamps.
  2. Have a stack of newsprint and printmaking paper (Somerset Velvet or Arches 88) torn down to correct size.
  3. Mark on the table WITH A PENCIL paper guides to aid in placement of the first color.
  4. Place small bits of Letraset tape (double-sided) to keep paper in place.
  5. Open the ink and put a generous amount of ink in a line at one end of the screen. You need more than you might think to facilitate complete coverage. Stop an inch or two past the stencil, though, as there is no benefit to squeegeeing where there is no artwork.
  6. Immediately do a flood coat:

    A flood coat is simply dragging the squeegee back over your stencil; once you have printed with the squeegee, lift the screen up slightly and drag the squeegee lightly across the surface. If you do not get complete coverage, you can either squeegee again (large dry area) or take a dollop of ink (small area) on your finger and dab it in the bare spot. Flood coating is vital to the quality of the print when using waterbased inks, as we do.
  7. Remove printed paper and set aside. Place a new piece of paper under screen and repeat until finished with the color. Immediately clean up the screen!

Helpful Hints:

The Mylar Registration Method

When using more than one color, you will need to formulate some sort of registration method. If you printed crop or registration marks, these can aid in mylar registration, but are not necessary for fairly straightforward separations.Once you have printed your first color, you need to know where to place your paper under the screen for the next color.

You can accomplish this by the following:

You can use Sprayway glass cleaner to clean off mylar in between colors, allowing you to use it again and again. This should work even after the ink has been allowed to dry.

Cleanup

Once you finish a color, you’ll want to:

Once you’re finished printing for the day, you’ll want to:

Reusing Stencils

Stenicls are pretty hardy, so long as you treat them kindly. This includes not exposing them to hot or warm water. If you would like to use the screen again, simply let it dry after you’ve cleaned out the ink using Wash-Away and water. Once it’s dry, you can use it again.

Reclaiming Screens

To reclaim a screen, do the following: