The series of works on paper produced between the late 1950s and early 1960s, explores the dialogue between shadow and light. The rhythmical modulation and variations on the theme of the grid, as well as the energy produced by the parallel lines, are clearly visible in these works.

This series was influenced by Mack’s early work on reliefs, which he created towards the end of 1950s by using pieces of embossed aluminium. These reliefs were subsequently used by Mack as a matrix for his drawings, through the use of frottage.

Mack defined these works as “graphical energy fields” as the frottage technique has the ability to give the paper a textural quality that the eye perceives as a vibrant modulation. By moving away from more traditional art and graphical practices Mack and the ZERO group were able to explore new types of art, which led to the discovery of pictorial spaces that were full of energy, where vibrations could be revealed.

"L'oeuvre est parmi les plus belles de cette série et en l'occurrence l'une des toutes premières. Elle est réalisée à la cire blanche sur papier noir, par frottage d'une plaque de métal embossée : une fois posé sur ladite plaque, le papier est frotté avec un crayon de cire, qui opère un transfert du motif de la matrice. La technique est unique. Elle caractérise les meilleures oeuvres sur papier de Mack à cette époque cruciale de sa carrière : celle des tout débuts du Groupe ZERO qu'il a fondé deux ans auparavant avec Otto Piene." - Matthieu Poirier