Saying an image consists of many layers sounds obvious, but i do believe intstant photography has one extra layer, which is the physical one. Even more than film in general, polaroids are objects that you can hold.
As a polaroid photographer once said, when you see a polaroid you know the photographer, and most likely everyone appearing on it, touched it. They passed it around and looked at it and reacted to it. It's a fetish in the animistic sense of the word.
The power of instant photography lays in the delivery of a full object where all layers are crushed together: the subject photographed, the emotional state and assotiations of the photographer that lead him/her to choose it, the light hitting on the sensitive surface, the chemical layers that conform the image, the emotional state and emotional experiences of the viewer... All together crushed into an entity, that is so true, so real that you're actually holding it. The idea behind the series 'Kuleshov' is blending realities by trying to intervene all of those layers at the same time.
In his experiment, Lev Kuleshov edited together a short film in which a shot of the expressionless face of an actor was alternated with various other shots (a plate of soup, a girl in a coffin, a woman on a divan). The film was shown to an audience who believed that the expression on the actor's face (always the same) was different each time he appeared, depending on whether he was looking at the plate of soup, the girl in the coffin, or the woman on the divan. The viewer projects him/herself and his/her own feelings on the image. He/She makes half of the work in constructing the image. To reach the viewer, ideally, a polaroid should be meant not to build an image but a perception.