Baumeister's late style culminates in his famous "Montaru" series. Features of this series, made between 1953 and 1955 and characterized by the continuation, combination and integration of pictorial elements from earlier periods, can be found in some of his works made as of 1951. The black color field dominating the image's center, a typical feature of pictures from the "Montaru" series, fragmented in the sense of a tense composition, can be found in the painting "Schwarzes Phantom" (Museo Thyssen-Bornemisza, Madrid) from 1952. Just a few months later, that was in January or February 1953, Baumeister eventually began working on the painting "Montaru 1", today in possession of the Sprengel Museums in Hanover, marking the birth of the “Montaru“ series. An onomatopoetic creation by the artist is eponymous, combining the words "mons" or"mont" (mountain) and the sound "aru", which hints at the pictures impervious darkness and is derived from the name of the biblical mountain Ararat. The blackness, which seems to expand onto and hover above the image surface, is in a characteristic constellation of tension with the image carrier. Further paintings from this impressive work complex are in possession of, among others, the Nationalgalerie Berlin, the Städtische Kunsthalle Mannheim and the Karl Ernst Osthaus-Museums, Hagen.