Initially he concentrated on portraits of nudes and, especially mother-and-child paintings, but moved ever closer to abstract art under the influence of Michel Stoffel and Lucien Wercollier with whom he became one of the founding members of the Nouvelle Equipe.
Thereafter, Probst was recognized as one of Luxembourg's classic artists, not just through local interest in his works but through exhibits at the Musée National d'Art Moderne in Paris and at the Universal Postal Union in Bern.
[2] His abstract style developed slowly from the early effects of his dark, subdued colours on form until his oils and guaches became ever more geometrical.
From 1955, he moved even further into complex, interwoven forms with an extended spectrum of colour, making him a true proponent of lyrical abstract art.
Representing variations on a theme, his mosaics depict visual versions of musical compositions such as Franz Schubert's Winterreise cycle.