How Does Polaroid Film Work?

Introduction

With digital cameras taking over the photography market, it's sometimes fun to reminisce of the old days of the Polaroid camera. Polaroids have long been famous for being able to take a picture and have it be developed right in front of your eyes. Though mostly nostalgic now, Polaroid cameras are still used in some applications even today.

Film Layers

Instant Polaroid film is made up of three different layers, each with a dye coupler layer between them. On top of these layers is an image layer, a timing layer and an acid layer.

Re-Agent

Polaroid film is essentially one big chemical reaction. This reaction is started by a product called the re-agent. The re-agent is a mixture of white pigments, opacifiers and alkali. The opacifier and alkali are especially important since the opacifier works as a light blocker and the alkali as an acid neutralizer. This combination of products is spread across the entire frame of the film. This is why Polaroids have a white frame around the outside of the film, as if the re-agent were to be on the film itself, it would start the chemical reaction before the film is ready to be developed.

Process

When you take a picture with a Polaroid camera, the camera automatically pushes out the film using rollers inside the camera. As the film exits the camera the reagent is spread across the film. This starts a large chain of chemical reactions. The colors from the dye layers are brought up from the lower layers as the chemical reaction continues. At the same time, the acid layer is working its way up to the top while the re-agent is working from above. Once the two chemicals meet each other, the alkali and opacifier react to make the re-agent turn clear. As the re-agent turns clear the image slowly appears until you have a piece of developed film.