Instant film cameras have the developing process of traditional film arranged inside them in chemical layers. Once exposed to light, the layers begin a chemical process that results in an instant photograph.
Instant film cameras have the same basic light-sensitive layers as traditional slide film. However, they also have layers containing the necessary chemicals for developing film. Traditional film contains a clear plastic layer, a black base layer, image layer, timing layer, acid layer and color layers. Instant film cameras contain all these plus developer layers with dye couplers, the chemicals that react with the color layers and begin the development process.
The process begins with a reagent, a mix of light-blockers, acid neutralizers and white pigments. Before a picture is taken, the reagent sits at the corners of the clear plastic film sheet to keep the film from developing. After a picture is taken, a pair of rollers inside the camera spread the reagent into the middle of the film sheet. The reagent moves downward through the rest of the layers where it reacts with the various other chemicals in the film. The acid layer reacts to the chemicals in the reagent, while the timing layer slows the reagent down, so the image has time to develop. When the photograph finally leaves the camera and is exposed to light, the light-blockers clear away, leaving the image completely visible.