To understand how instant photographs work, it is
necessary to understand how a colour film works. A colour film consists of
three layers that are sensitive to different colours. The top layer is
sensitive to blue light, the next layer reacts with green light and the last
layer is responsive to red. Each layer is coated with light- sensitive silver
particles, which form into metallic silver after light is shone on them.
The component that starts the developing process is
the reagent. The reagent is a mix of opacifiers, which make an object opaque,
and alkali pigments. The reagent can be found between the image layer, which is
on top of the reagent, and the three light-sensitive layers. Before you take
the picture, which starts the chain-reaction, the reagent is collected in a
blob separated from the light-sensitive material. This prevents the film from
developing before it has been exposed.
To sum up the information so far; the polaroid picture is a film which consists
of a number of layers. Each layer contains different chemicals, which makes the
developing process a step by step process.
The first step is to take the photograph. The film sheet is pressed out
of the camera through rollers, which sets the reagent in the second layer free.
The reagent starts the reaction with the other chemicals in the different
layers. At the same time the opacifier prevents light from filtering to the
layers below, so that the film is not exposed before it is developed. The
chemicals are now moving down through the layers and turn the silver grains into
metallic silver. Simultaneously, the chemicals dissolve the developer dye and
the dye from the undissolved layers moves up to the image layer. For example,
if the magenta layer was exposed than no green dye will wander up to the image
layer.
While the chemicals work through the layers that
contain the dye, the reagent and the alkali make the opacifier become clear.
That way an image can be seen. This means that when the image appears, the last
chemical reaction can be seen. Since the photo is already developed underneath.
The last thing that happens is the opacifier clearing up, making the image
visible.
[378 Words]
