Each color requires a separate screen. The design is then “burnt” into each screen. Screens consist of fabric stretched across a frame. Each screen is then coated with a light sensitive emulsion that hardens when exposed to bright light. The print out of the design is placed on top of the screen and the screen is placed on the exposure unit. When the exposure unit is turned on it directs a bright light at the screen.
The emulsion that was hit by the bright light embeds in the fabric of the screen. The emulsion remains soft where the design blocked the light. That soft emulsion is then rinsed out, leaving behind a perfect duplicate of the design.