Kurt Rudolf Hoffmann was born in Sonderborg, Denmark on April 5, 1923.

Sonderborg went to school in Hamburg, Germany and completed a merchant's apprenticeship in 1939. He became a private student of the painter Ewald Becker-Carus in Hamburg in 1946. From 1947 to 1949 he studied painting, graphic art and textile design at the State Art School in Hamburg under Willem Grimm and Maria May.

In 1951 artist Kurt Rudolf Hoffmann began calling himself K.R.H. Sonderborg, after the town he was born in. Starting in 1953, he became a member of the group “Zen 49” and he went to Paris the same year where he learned engraving from Stanley William Hayter in the Atelier 17. Paris is also the place where he first encountered Tachism. In the years following the artist continued his travel and worked for some time in London, Cornwall, New York, Ascona, Rome and Paris again. While in New York, Sonderborg came into contact with Action Painting and Abstract Expressionism.

His own style is became more abstract, painting using swift, gestural strokes that reveal the painting process, with spontaneous color application. Black and white contrasts are an important feature, later he added colors such as cadmium red.

K.R.H. Sonderborg exhibited in the 1958 Biennale in Venice. He was awarded the Prize for Graphic Art at the Biennale in Tokyo in 1960 as well as the Great International Prize for Drawing at the 1963 Biennale in Sao Paulo, Brazil.

From 1965 to 1990 Sonderborg held a post as professor of painting at the Stuttgart Art Academy. In 1969/70 he was a guest lecturer at the Minneapolis College of Art and Design, as well as at the Art Institute of Chicago in 1986.

K.R.H. Sonderborg died in Hamburg, Germany on February 18, 2008.