If there is any one thing that absolutely cannot be enlarged it is the sky. A photograph of a clear, cloudless day with no terrestrial references is either absurd or a paradox. So from the balcony of my home, toward sunset, I used a whole roll of film with various images of the sky, holding my camera both vertically and horizontally. The resulting sequence is rich in gradations from one photogram to another, in terms of depth, intensity. Then I chose one photogram and enlarged it as much as I could, so that you could see the grain. The third process was enlarging a tiny detail of the previous photogram as much as my studio allowed me to: from a detail measuring slightly more than three centimetres to almost three-and-a-half metres. At that point the sky disappeared and all that was left was a grainy surface. The dominant element was the clumps of silver salts, the graininess. You realise you could get the same image by photographing a wall, in other words, the image is reversible, interchangeable.