From 1949 to 1950 he studies art history and German at Cologne university. Then he studies under Willi Baumeister and Rolf Henniger at the Kunstakademie in Stuttgart from 1950 to 1953. During these years Gaul makes, while staying in Paris for the first time, his acquaintance with Jean-Pierre Wilhelm, Pierre Restany and Julien Alvard. In 1955 Gaul moves in a studio in Dusseldorf-Kaiserswerth. Gaul also wins Manfred de la Motte and Peter Brüning as his friends. He has his first single exhibition at the Gallery Gurlitt in Munich in 1956. Apart from photograms he does together with Peter Brüning his first print graphic is created. That year Gaul becomes friends with Karl Otto Götz, Bernard Schultze and Heinz Kreutz. In 1961 it comes to a change from Informel to the 'Verkehrszeichen und Signale' (traffic signs and signals). At the motorway Milan-Monza he puts up his first traffic sign in 1962. From 1964 to 1965 he works as a guest lecturer at the Staatliche Kunstschule Bremen. From 1967 to 1972 Gaul lives in Antwerpen. During this period he makes a sketch of variable system for a geometrical environment. For the Süd-Asien Institut of Heidelberg university he creates three coloured steel sculptures from 1969 to 1972. In 1973 a big touring exhibition takes place calling at Munster, Ludwigshafen, Ulm and Bielefeld. Gaul participates at the documenta 6 with works from his series "Farbmarkierungen" in 1977. In connection with the publishing of the work index of his print graphic and objects, the Kunsthalle Kiel organizes an exhibition of the complete print graphic in 1978. The Pinacoteca Macerata shows a retrospective of the draughtswork in 1982. Apart from single pictures, drawings and water colour pictures Gaul creates after 1983 a series of pictures in several parts and a triptychon which he dedicates to Claude Monet.