Sheets of clear plastic, containing the images of the characters, which are placed over a background, and then photographed in succession to give the illusion of movement in the completed film. The outline of the image, whether hand-inked or xerographed, is applied to the front of the cel. The colours are painted by hand onto the back of the cel to eliminate brushstrokes. Large areas of black paint were sometimes applied to the front of the cel to reduce glare.