Because many people don’t know what silkscreen printing is, I’ll do a brief primer on it. I took some photos at the School of Visual Arts printshop to help illustrate some confusing passages.
Silkscreen Printing is printing an image through the use of a silk mesh stretched over a frame(called silkscreen). Unlike most printing methods (woodcuts, etching , letterpress) where you need to create an image that is mirrored (or backward), your image doesn’t need to be flipped at all. Also, most printing methods need a press to push the inked plates onto the substrate. In silkscreen, there’s no need for a press. The printed image lies on top of the substrate, which is why you’re able to print on virtually any material with silkscreen. Essentially, with silkscreen, you are creating a stencil. Open areas of the screen will allow ink to go through the screen and print onto the paper or what have you.
So assuming, you have already created an image to be silkscreened, the very first step in the process is creating separations of the image. You need to draw with a black marker on vellum or acetate…or you can also print from the computer (although you need a special printer and paper). The black areas represent the areas that will be open in the screen and allow the ink through. So although the separations are black, doesn’t mean that you’ll be printing with black ink.
To create the stencil on your silkscreen you first need to coat your silkscreen with emulsion, which is a photo-sensitive liquid. So you go into a dark room, put some emulsion into the scooper and then spread it over the silk mesh in a thin and consistent layer. It’s important that the emulsion is thin on the screen so the stencil won’t peel off later on.
Here’s a picture of a coated silkscreen.
Now you need to expose the screen with lights to the your separation. In this case, I use a massive exposure unit which contains a light table, a vacuum and a timer. You put the separation on the light table, right side up and then lay the screen on top, screen down. The separation needs to be pressed tightly against the screen or else you’ll get a stencil with fuzzy edges; which is why there’s a vacuum pump in the exposure unit.
Exposing the screen in theory is just like exposing film in a camera. In this case, the emulsion isn’t as sensitive, so you need to expose for a couple of minutes to UV bulbs. Once the screen is exposed, it needs to be sprayed with water. The idea is that the light completely dried out the emulsion on the screen, except for the areas that were covered in black by the separations. So those areas can be washed out with water and that’s how you create your stencil on the screen.
We’re one step closer to actually printing! Next, the screen needs to be secured to your working area with hinges that allow you to lift the screen up. Having the screen securely clamped in the hinges is one of the many steps you need to take to ensure proper and consistent registration (lining up) for all the copies you’ll be making.
The second step is to align the separation to the paper you’ll be printing on. And then tape the two together (you’ll be removing those later). And then line up your screen with your paper-separation.
After everything is lined up, now you know exactly where every single print needs to be relative to the screen. You can tape metal tacks to the table top, making sure they’re completely flush with the page. And you can also remove the separation from the paper.
. And now, the moment that all this preparation has been building up to: PRINTING. You need ink, and a squeegee.
Spread some ink at the bottom edge of your screen. And use the squeegee to spread the ink upward. This is called “flooding” and preps the screen with enough ink to actually print through the screen. And lift the screen up as you’re doing so. You can put a new piece of paper in the registration tacks,, lay the screen down and use the squeegee to drag the ink back down. Lift the screen up, and look at your print.
Now put this print on the drying racks and load a new piece of paper. Flood the screen back up, lay the screen down, push the ink down, lift up the screen, put print on drying rack, put new piece of paper, and repeat the process until you’ve made all the copies you’ve wanted to make.
You can now erase the stencil from your screen by soaking it in reclaimer and then using a powerwasher to wash off the dried emulsion. Start the whole process again for the next color/separation in your print. I use pretty big screens, so I can fit several separations on my screen and save time. The next passes of color is pretty much the same process, only now it becomes very obvious if you mess up registration. That’s a headache for another time.