Screen-printing is an extremely versatile process, and lends it's self to experimentation and alternative processes. One of my favorites is printing with watercolor inks. This easy process lets you create artwork that mixes the control of the screen with the loose, painterly qualities of watercolor inks.
The important thing here is that you need to use watercolors. They can be any type of watercolor, I've used watercolor crayons, tube watercolors, tray watercolors, and my personal favorite concentrated watercolors such as Dr. Ph. Martins. Watercolors will reconstitute when they get wet, paints such as acrylic or tempera do not reconstitute in the same way and can permanently dry in your screen.
You can use either an open screen with no stencil or a screen with a a traditional stencil. For this print I am using a screen with a stencil, in this case it is some artwork made by my friend Alison Tharp.
I'm using concentrated watercolors because I want this print to have vibrant colors, the process is the same for all types of watercolor paints. Using a wet brush, paint the watercolors on the inside (non-squeegee side) of the screen. You can be as precise or loose as you would like, here I'm being very loose. If I was using an open screen then the entire watercolor painting would print. Here, the stencil will control where the ink will print. Once you are done painting the the screen, let it dry completely.
I use transparent screen-printing base is to reconstitute the watercolors, and to push them through the screen and onto the page. Print the transparent base as you would normally print with ink. Run a nice line of base at the end of the screen, and with the screen propped up off of your paper flood the screen. Drop the screen down and print the clear base, using a lot of pressure. It takes some pressure to push the dry paint out of the stencil.
I can usually get about 4 good prints from each watercolored screen. As the watercolors are printed out the final image will print lighter and lighter. Once you are done printing, be sure and wash the screen out thoroughly, if the clear base dries in the screen it will wreck it.
I really enjoy this process as it can bring a softer, more painterly touch to the rigidity of screen-printing. The results can be unpredictable, that's what makes it so exciting.