 By 1905, he was developing some experimental techniques, including drawing with a needle on a blackened pane of glass, resulting in fifty-seven works including his "Portrait of My Father" (1906).In the years 1903–05 he also completed a cycle of eleven zinc-plate etchings called "Inventions", his first exhibited works, in which he illustrated several grotesque characters.He commented, "though I'm fairly satisfied with my etchings I can't go on like this.