Guide to Screen Printing

I love to screen print, so I thought I'd write a little bit about how to do it. It's really easy to get great results, but you have to know a few tricks.

First of all, NEVER buy screens or ink from an art store. For Whatever reason, there is a monopoly on ink and screen that is available from art stores. The company that holds the monopoly is Speedball, and they make screen printing equipment that is so bad it is almost unusable. The screens are impossible to tighten, the screens clog up easily, the ink washes out of the things you want it to stay on and stays on the things you want to wash it out of. I will list the phone numbers of a professional screen supply place at the bottom.

Choosing a screen: You can buy and re-use pre-stretched screens, and I would recommend it, they cost around $20 and save you a lot of hassle. There are two things to think about when buying a screen: mesh count and size. To determine the size of the screen, figure out the size of the image you want to print, and leave yourself at least 3 inches on every side of the image. If your image is 8 x 10, you need a 14 x 16 screen. Screen mesh depends on the kind of ink you are using and what you are printing on. There are recommendations that the screen printing people make, and you can follow them, but I have had pretty good luck using the following: If you're printing with white ink, use 110 mesh, colored ink on shirts or patches, use 156 mesh, colored ink on paper, 190 + mesh. The mesh refers to how many threads there are per inch.

In order to make an image, you need some photo sensitive emulsion. I use Ulano TZ emulsion, which costs around $20 for 20 ounces, which should be good enough for 20 - 40 screens. I mix it as I need it, and keep the unmixed parts in the refrigerator so that they will keep longer. I use a squeegee to spread the mixed emulsion on the screen, scraping off excess until only a thin layer is left. I then leave the screen somewhere clean, cool and absolutely dark for a day until the emulsion is dry. I take the image I want, and photocopy it on to transparencies. I use two layers of transparency and line them up very carefully, using scotch tape to hold them together, so that the blacks are darker. I then use a little bit of tape to keep it from sliding, and place it on the inside of the screen. I cover the transparency with a piece of glass so that it is pressed firmly against the screen. Then I wrap the whole works in something that will keep out light, like a towel. As long as you are not in direct sunlight, you can work at a normal pace and not worry about the screen being exposed.

I expose my screens for a minute and a half in direct sunlight. It means that you have to wait for a day when the sun is shining, but using a light bulb produces really unpredictable results, unless you have the money for a professional strobe, which you don't, or you wouldn't be reading this. After the screen has been exposed, I wash it out with a hose or shower, any hard spray of water, hot or cold.

I really like a water-based ink called Aerotex, which is made by Union ink and available at the stores listed below. It is easy to clean up, since you only have to use water, and it stays forever on fabric, without heating, due to a system in which you add a tiny bit of catalyst to the ink. White ink is really really hard to work with, since it is as thick as paste and hard to squeeze through the screen. For white on black, I use Plastisol inks just like everyone else. The problem with plastisol is that it has to be heat set, the whole surface of the ink has to reach 300 degrees. I use my oven to heat shirts, but I haven't worked out an accurate temperature or time which works yet, and plastisol has a habit of catching on fire, so be careful.

Midwest Sign and Screen Printing Supply: Hayward CA: 510-632-5800 Kansas City MO: 816-333-5224 Portland OR: 503-224-1400 Seattle WA: 206-433-8080 Denver CO: 303-373-9800 Omaha NE: 402-592-7555 Salt Lake City UT: 801-974-9449 Milwaukee WI: 414-423-1200. The Hayward branch, and maybe the others, have free shipping via UPS.

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