Getting the Artwork On Your Screen:

Originally, stencils were painted onto the screen by hand, which means you had to have a steady hand. You’re welcome to try that if you want, and by that I mean if you want your design to look crappy. Fortunately there is this stuff called photographic emulsion that makes it a lot easier. It’s basically some photo-chemicals mixed in with an Elmer’s glue smelling substance.  You apply a thin coating to both sides of the screen and let it dry in the dark.  If the dry screen is exposed to UV rays like the sun, the photo-chemicals react to make the already dry screen mostly impervious to water. To make a stencil you just need a sheet of clear film or transparent paper with dark artwork on it. The dark spots block the light from hardening the area beneath it. You expose the screen to light for some time and then take the artwork (called a film positive) off before you use low pressure water like a garden hose to wash out the soft areas. It’s called a positive because it is a positive image of everything that gets printed in a certain color.  You’ll need a film positive for each color present in your design.  There are other methods for making stencils, but this is the easiest.

Artwork:

You can hand draw it on film or vellum (like tracing paper) using dark liquid ink. Permanent markers don’t provide dark or even coverage and aren’t good for much  besides a small touchups.  There is also special film you can get for use on copiers that can work with varying, unpredictable results.  One of the easiest and cheapest ways to get consistently usable results is to use a laser printer to print on vellum or film. Make sure you use special film if you are using a laser printer or you will probably melt the film onto the rollers of the laser printer! Inkjets can also be used for printing on film. There’s no heat danger there, but some inks require a special film to adhere to. Office supply stores will have this. If you use a printer you can either scan hand drawn art work or use a drawing program.  Your artwork needs to be black and white, with no shades of gray. Even a crappy copying machine will make what will appear to be a gray image. For screen printing you need high contrast artwork made out of black parts and white parts with no grays. The white part stays the color of your board, and the black part will be printed in whatever color ink you use.  Each color needs it’s own film positive. If you’re new to screen printing you should start with a simple one color design. I’ll go into multiple color printing later.

Coating the Screen:

You can skip this process by taking your screen to a local screen printer and asking them if they will coat and expose your screen for you. This costs around $10-$50 a screen depending on how friendly or not busy your local screen shop is. Some won’t do it at all. I always remember it being a pain in the ass when I was in the business. All kinds of kooks would show up asking you to drop everything and do burn a screen for them. Since you are reading this I’ll assume you are the real DIY kind who is broke or not afraid to spend time learning it. 

You’ll need emulsion and a stretched screen. For starters I’d recommend buying one pre-stretched. I’ll talk more about making them yourselves later. You can order screens from a craft store, art supplies store, the internet, or better yet, your local screen printing supply company found in your phone book.  You’ll need a loose screen with a medium high mesh count, more on that later. You’ll need emulsion, too. A general purpose emulsion usually fine. They do make different emulsions for different uses. To coat the screen you’ll need a scoop coater that fits inside the shortest dimension of your screen. You’ll want a two inch plus gap on each side or you won’t be able to get a clean and even coverage. Don’t worry about the ink seeping through the edges because hopefully you won’t be that much of a slob and will use clear packing tape on the inside of the screen to cover where the screen meets the frame.  Scoop coaters are sold by the inch and custom cut to your specs. Most places will keep common sizes in stock.  If the thought of spending 20 to 30 bucks on a scoop coater bums you out, you can make your own out of thick paper or thin cardboard that will do the trick in a pinch if constructed well, but will not last long.  You’ll also get less than perfect coating which will make it hard to consistently expose screens and might even render areas of the screen unusable. You could also use aluminum angle iron or something similar as long as you cap the ends and sand the leading edge smooth to prevent it from ripping the screen.  You’ll get tired of hearing this, but I’ll discuss ideas for making your own scoop coater later.  In any case, this is one area where it pays to buy a legit coater once you’ve settled on a common screen size since they are relatively cheap and will last forever.

Before you coat the screen you need to degrease it. Degreasing a screen will clean off the oils and chemicals present on the mesh that can prevent the emulsion from adhering to the screen. Even brand new mesh has oils on it from the rollers and themachinery used to loom the fabric. Degreasing a screen is easy. Just get some purpose-made screen degreaser or even a mild laundry soap and a soft brush. Spray the mesh with a hose, dip the brush in the degreaser, and scrub both sides with light pressure. Then rinse the screen well and let it dry. If you buy screen degreaser you have the option of diluting it to make it last longer. Wear gloves. Degreaser can irritate your skin. Calgon, take me away.

Fill the scoop coater with emulsion. You don’t have to be in a pitch black room. You can use a red darkroom safelight, to coat and dry screens.  You can even a yellow bug light, or normal light bulb, just don’t do it outside in the sun. Hold the screen almost straight up and down. Place the edge of the coater against the screen a couple of inches from the top of the bottom frame, on the outside of screen.  Tilt the coater against the screen until the emulsion builds up a wall against the entire length of the screen, but doesn’t overflow the edges of the coater. In a smooth and steady movement, drag the coater up to the top of the screen, being careful to keep the emulsion covering the entire width of the coater during the whole time. Stop a couple of inches below the bottom of the top part of the frame. It’s likely that your screen will be longer on one of the dimensions. The scoop coater should fit inside the narrowest of the dimensions. Coat the outside of the screen 2-3 times before flipping the screen over and doing the same for the inside of the screen.  If for some reason your coater is really short, coat against one side of the frame first, then the opposite. You’ll have an area of double coverage in the middle which you give one last coat one last time from the middle before flipping the screen over and repeating.

Slow and steady is the way to go. If you stop mid-stroke you will leave a notch in the emulsion that will likely mess up your image. Don’t go too fast either or your coverage will be uneven. Coating the inside last will push more of the emulsion to the contact part of the screen which will help give you a crisper image and better ink coverage. Some shops will even  give the bottom of a screen a second coat after the first one dries. This can give you even more ink coverage as well as a longer lasting screen. The downside is the extra time to coat and the increased exposure time. It’s not rocket science, so don’t worry if it’s not perfect. Just try to get as smooth and consistent of a coat as you can.

Immediately after coating a screen, put it into a completely dark or safelight room. You don’t even have to use a whole room. It can be a closet or a box as long as it is cool, dry and light safe. Set the screen horizontally with the outside of the screen towards the ground. Make sure the screen is raised from the ground by placing something under or near the corners of the frame. ,Old skateboard wheels work great for this. You can stack them this way too, or build a drying rack that hold the frames by the edges.  It is important that your drying room be light safe and clean. Even a small light leak can expose the screen if it is left long enough, and a dusty room will attract particles to the screen which will mess up the image and even cause undue wear on the screen by acting like sandpaper. Ok, that’s a bit of a stretch. Keep your cats away too. One of mine has an uncanny knack for jumping on freshly coated screens.  A fan can be used to speed the process as long as there isn’t a bunch of crap floating around in the air.

Next Page: Exposing the Screen