The Films
Photo by Felix

I took the paste up to the graphic supply place and they made a film positive for me. You could easily do this yourself if your laser printer can print on transparencies or you can photocopy onto transperancies. If you photocopy you will probably have to layer two or three because the ink isn't very solid and light passes through it.

The basic principle is that the screen is coated with a light sensitive chemical emulsion. The film is laid over the screed and exposed to a powerful light long enough to cure the emulsion. Then the screen is powerwashed and in the areas covered by the film the uncured emulsion washes out.

You can do this yourself with a floodlight and a home made "exposure unit" but I was rushed for time and didn't want to buy a bunch of chemicals so I just had the screen shop do it.