Castellani made his first “Surface in Relief” (“Black Surface in Relief”) in 1959, exploring a creative process that was to become the starting point for all his subsequent research. It consists in placing the surface of the canvas, strictly monochromatic, in tension by means of alternating indentations and protrusions, created by two levels of nails placed against the canvas. This research dimension, which goes beyond the picture and painting, draws inspiration from the work of Fontana, an essential reference point for young artists working in the environment of Milan between the 1950s and 1970s. Fontana was featured in the opening article of the first edition of “Azimuth”, the magazine founded by Castellani, together with Manzoni and Agnetti, in 1959 (published in two editions in 1959 and 1960), aimed at documenting the artistic debate beyond Informalism. “The need for the absolute that stirs us, inspiring new subject matter,” wrote Castellani, in the second edition of the magazine, “prevents us from using the conventional means of pictorial language. Since we have no interest in expressing subjective reactions to facts or feelings, but desire our discourse to be continuous and total, we exclude those means of language (composition and colour) that suffice for limited discourse, metaphor and parable, and are freely revealed, considering that, as their multiformity requires a choice, they raise spurious problems that are not essential to the development of art.” Castellani revealed on that occasion that this new artistic dimension, through “the process of an elementary entity, a line, an indefinitely repeatable rhythm or a monochromatic surface”, can give the works the “concreteness of the infinite” and “bear the conjugation of time, the only conceivable dimension, the yardstick and justification of our spiritual needs”. All this is seen in “Surfaces”, in which the perceptive effects created by the indentations and protrusions dilate space and make it dynamic.