Now after exposing it to the sun, the screen is then washed out with water using a water hose. The black or red image on the film positive did not let any sun get to the photo emulsion, therefor the unexposed photo emulsion can then be washed out, the other has been hardened by the sun light and can not be washed out. now after the screen has dried. you can use it to print your image with over and over as many times as you like.