Painter and graphic artist, one of the most important Austrian artists of the 20th century; 1906-1909 attended the Vienna Academy of Fine Art and was one of the founders of the group of artists known as "Neukunstgruppe" in 1909; from 1909 he took part in numerous Austrian and international exhibitions.
More widespread recognition only shortly before his death through a group exhibition in the Secession gallery. S. developed a unique style which was mainly due to the influence of Gustav Klimt (friendship from 1907) and East Asian art.
He blended ornamental surface outlines with an expressive language of often vivid colours. The self-portraits, portraits, nudes and figures which constitute the main part of his works apart from landscapes, often express suffering, pain and loneliness and frequently depict the conflict of Death and Eros.
The erotic directness of his nudes seemed to pose less of a problem than S.´s interest in and depiction of minors, which resulted in his being sentenced and imprisoned for a short time (in Neulengbach and St. Pölten).
In contrast to the landscapes and figure paintings of the time before 1915, which are often characterised by an unusual perspective, the later works tend to be more calm and harmonious. S.´s works are found in many internationally important collections. The Albertina Graphic Collection in Vienna houses a major part of his drawings and the largest collection of S. documents in special S. archives. S. museum in Tulln.