Chapter 3 – Screen Printing Basics (part 1)
In January 2008, I went to my first screen printing class and, as they say, the rest is history. I met what would become my primary medium for creating art. I found a tool that would allow me to get words onto fabric, regardless of the final outcome of that fabric. So, how does this work? Elsewhere on my website, under News, dated October 30, 2013, is a link to a video that shows me screen printing. That video shows the outcome part of screen printing, which is getting the image from the screen to the fabric. There is a lot more that has to occur for that outcome to manifest. This chapter (in two parts) is about that process.
One begins with a screen. You can create your own screen, using mesh screen fabric and a wooden frame; however, I choose to let others do that for me, so that I have a nice taut screen. I have 40-50 screens, ranging in size from 8 x 10 inches to 24 x 36 inches. The image on the left shows a blank screen. If you look closely, you can see the ghosts of old images that were on this screen. A nice property of screens is that once you are done with the image, you can reclaim the screen by subjecting it to a chemical and scrubbing it clean. Given you can reclaim screens, why do I have so many of them? I keep screens that I know I will use again and again. All of the screens in my studio have an image (or multiple images) on them that I use enough in my work that it would not make sense to have to create a new screen every time I needed that image. I keep about ten blank screens at home, for use with new and temporary images.
Creating a screen is a labor of love and patience. In my first screen printing class, I had more failed attempts than successes when it came to creating a screen. There is science involved and the slightest miscalculation can lead to a failed attempt at creating a screen. I will first explain the process, then discuss some of what can go wrong with that process.
The process I use is a photo emulsion process. By using a photo emulsion process, I use light to “burn” an image onto the screen. First, I have to have an image. The easiest way to begin is with a piece of transparency paper, 8 x 10 inches. Using a permanent marker, such as Sharpie, I draw an image onto the transparency sheet. I create both bold and fine lines in the drawing, where possible, in order to create variable images on the screen. I usually create the image first, as this will dictate the size of screen I will need.
Once I have an image, I can now turn my attention to the screen. I coat the screen (both sides) with a photo emulsion. Given this is photo emulsion, it is light sensitive. So, I have to work with darkroom lights so as to not expose the emulsion prematurely. My darkroom lights are amber (some are red), as amber does not create the type of reaction of regular light bulbs, which include blue and green light. Some of the photos for this chapter have a yellow tone to them because I had to photograph them with the amber light, which is the only light in my darkroom. To get the emulsion onto the screen, you use an emulsion spreader, which is the long trough looking item in the top image. You want to get just the bare minimum of emulsion onto the screen. People use different techniques here; I do one coat on each side of the screen. You want to use emulsion that is not too old, as it will deteriorate, leading to poor results.
Once the screen is coated, it must dry for at least eight hours, though I prefer to let it sit overnight, to account for humidity. The screen must dry in a darkroom setting or a drying (light-free) cabinet. Once the screen is dry, it is ready to be exposed to light and, if all goes well, become a screen that can be used for printing.
I now have an image on a transparency and a coated screen. Now I need an exposure unit. When I first learned to do this, I used an exposure unit at the local Art Institute. However, when that unit broke and went months without repair, I opted to purchase an exposure unit for my own use (the image to the left). This is a table top exposure unit, that can handle screens up to 25 x 36 inches in size. With eight fluorescent bulbs, it provides strong, uniform light for exposing screens. Each exposure unit, coupled with different emulsion (both type and degree of coat), means different exposure times. After much experimentation (read failed screens), I was able to determine just what I needed to “burn” my own screens.
This takes us to the next step – “burning” the image onto a screen. I take my transparency with the image I want and place that on the exposure unit. I then place a coated screen on top of that image, centering the image as best I can. I then place thick foam into the opening of the screen, place a heavy board (melamine shelves work great here), a giant towel to cover the entire unit, and then press the light button. I expose each screen for three minutes (this could change with different emulsion). This is where the magic happens. Imagine seeing this screen sitting on its edge, coated with emulsion (my emulsion is pink). Lay a transparency against the screen. Now you can see only some of the emulsion. When the light hits the screen, it hardens the emulsion. Where the transparency is dark (opaque), the light does not get to the emulsion and the emulsion does not harden. Given the permanent marker does not create a perfect light barrier, some light will get through, but if you time the exposure correctly, there should not be hardened emulsion where you want the design/image to be on the screen.
Now comes the last step and one that can take a great deal of time, especially if one does not have a power washer. You take the exposed screen and scrub off the emulsion that did not harden. You use a soft brush, such as the one in the top image, and a soft touch, as it is all too easy to scrub off more than you want. A power washer on a low setting can be very helpful in cleaning out the emulsion that did not harden. I use a sink spray nozzle, which takes a lot more time, but gets the job done.
Things that can go wrong in this process include the following: (1) too much emulsion, which makes it difficult to wash off what you want; (2) too little emulsion, which usually results in the whole screen washing out with no resulting image; (3) too little light exposure, which impacts how the emulsion sets and whether it will stay hardened around the image; (4) too much light exposure, which causes all of the emulsion to harden; or (5) the wrong size mesh on the screen. Given I work with fabric, I have to use screens that have less of a tight weave (e.g., rather than 220 threads per inch, I work mostly with 60-130 threads per inch). When the weave is not right, it can be difficult to transfer the image to fabric.
By the way, you do not have to use a transparency to create an image. You can use other things, as long as there is an opaque factor. For example, I have used children’s halloween costumes, such as wings, to create an image. An example is to the left.
Stay tuned for part 2 of this chapter, where I discuss the process of using screens to get images onto fabric.