The ink
Photo by Felix
Here's the ink I used. It's a general purpose ink for printing on all kinds of surfaces.
When you buy your ink make sure you get all the info on it right away. Some ink is water based and some solvent based. Solvent based inks might clean up and thin with Mineral Spirits (paint thinner) or Laquer Thinner. Also some ink is heat cured meaning you need a dryer, heat gun, etc. For most things like this you'll want an ink that air dries, unless of course you have a dryer or access to one. The main problem with printing stuff like posters and air drying them is that you run out of space really fast to lay them out to dry. With a dryer you are fully curing the ink and stacking the work as you go.
For this job I used a "retarder" in the ink. The first time I tried to print these posters the ink dried in the screen right away, it was a hot humid day and I had to wash out the screen with Laquer thinner and go buy this retarder to keep it from drying too fast. If I'd been smart and asked a few more questions when I bought the ink I would have known that an ink with a drying time of 15 minutes wasn't going to last long in my screen on a 90 degree day before it started to dry up.