the complementary dye below it, reproducing the original color. For example, a photo of a blue sky would expose the blue emulsion, blocking all the yellow dye beneath it and allowing the magenta and cyan dye layers to migrate to the positive to form blue. Integral film This process is similar to subtractive color instant film with added timing and receiving layers. Land's solution was to incorporate an opacifier, which would darken when ejected from the camera, and then become clear to reveal the photograph. The film itself integrates all the layers to expose, develop, and fix the photo into a plastic envelope and frame commonly associated with a Polaroid photo. There are two kinds of integral instant photographic film: one where the side that is exposed to light, is opposite to that used to view the photograph, and another where the same side is used for exposing the photograph and viewing it, developed by Kodak. Again to develop the film a pod with a reagent on one side of the film is broken and the contents are spread within the integral film. For films with the same view/expose side the reagent had white pigment, opacifying dyes, potassium hydroxide, and a thickener, which would be spread on top of a stack of (from top to bottom) cyan dye developer, red-sensitive silver halide emulsion, an interlayer, magenta dye developer, green-sensitive silver halide emulsion, an interlayer, a yellow dye developer, a blue-sensitive silver halide emulsion, and an anti-abrasive layer. This stack would be on top of an opaque polyester back. Above the reagent would be an image-receiving mordant layer, a timing layer, an acid layer and a clear polyester layer. The pigment would be white titania in a suspension, and the opacifying dyes would be opaque at high PH levels but mostly transparent at low PH levels. The developers would contain metals such as copper for cyan, and chromium for magenta and yellow. These would form metal-containing dyes, with better lightfastness. Eventually this type of film from Polaroid received a silver-ion catalyzed process for dye release for the magenta and yellow dye layers. The reagent is highly alkaline and when spread across the top of the stack, it solubilizes or dissolves and moves the chemicals in the stack, which starts the photographic developing process. The silver halide that is exposed to light undergoes redox reactions with developer, and leaves free, undeveloped silver