How Instant Photographs Work

The world of photography has changed since Edwin Land introduced a remarkable new invention to the world in 1947 - instant photography. Ever since the invention of the Polaroid camera, we could not imagine a world without it anymore.

I assume that nearly everyone knows how a Polaroid camera looks like and what needs to be done in order to take a picture, but do you actually know how the film is developed inside the camera? After pressing the shutter release button on the top of the device, the picture appears in a matter of minutes. In order to be able to fully understand the physics behind a Polaroid camera, it is essential to first be familiar with the basics of traditional photographic film.

Normal film is composed of plastic base coated with particles of light-sensitive silver compound. A black-and-white film has one layer of silver compound. When the film is exposed, the sensitive particles react to the light by changing their structure. To create an actual photograph, the film would then have to be treated with several chemicals. The instant film, however, already provides the developing chemicals in the different layers itself.  

The light-sensitive layer lies on top of the black base layer, which is under the image layer, the timing layer and the acid layer. This specific arrangement of the layers contributes a great deal to the quick developing, as it creates the environment for a chemical chain reaction. This reaction is triggered by the reagent, which is situated just above the light-sensitive layers. The reagent is composed of a mix of opacifiers, alkali, white pigments and other elements. As soon as the image is captured, the film sheet is ejected out of the camera through a pair of rollers, which spread the reagent material onto the sheet. As the reagent chemicals move through the individual layers, the exposed particles are changed into metallic silver. At the same time the developer dye is dissolved by chemicals and diffused up into the image layer. However, only the dyes from the unexposed layers will reach the image layer. The opacifiers and alkali in the reagent then react with the acid layer, making the opacifiers clear so that a visible image is created.

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