“Iridescent Interpenetration No.7”, from around 1912, in a frame shaped by the artist with elements that reflect the compositional theme of the work, depicts the shading of colours from purple to blue, green and yellow in a series of mirrored triangles, as if broken down by passing through a prism. The work is directly linked to a number of studies in his German notepad and follows one of the most commonly used motifs for portraying “irides”. The term was introduced by Balla himself in some letters sent from Germany: on 21 November 1912, the artist sent his pupil Gino Galli a postcard in which he speaks of a “type of iris” to be perfected and given “an even better fusion” by painting an abstract composition with equilateral triangles in watercolours. In a second letter to his family, on 5 December 1912, he paints a triangular pattern, speaking of “this little iris... resulting from... endless trial and error and finally finding the goal of delight in its simplicity”. On the other hand, the diffusion of light and the representation of the ranges of colour derived from the rainbow is what attracts him most during his stay in Germany, starting from his journey there across the Alps: “Before reaching Gotthard, the lakes, with the huge mountains reflected in the water with iridescent colours, produce such effects that it is better to consider them unpaintable...”. In Dusseldorf station, he admired the “beautiful stained glass windows with yellow and blue triangles and squares”, and was fascinated by the “tall, coloured windows with the vaguest shades of colour” in the city’s cathedral. Neither does he fail to mention the modern artificial lighting, with “phosphorescent and fantastic effects” that animated the great city on the Rhine (letter reproduced in Fagiolo dell’Arco, 1968, p. 18). Balla’s studies on the iris, which he had perhaps already begun in Italy in his involvement with the nascent Futurism, were cultivated more intensively in Germany, where he could concretise his research through the formal models commonly found in the German culture of that time. The process towards a new representation of movement and light occurred in this period, with the discovery of the propulsive motion expressed through the triangle, which was of decisive importance for the abstraction of the speed of cars in years that followed.