George Claessen gained his highest accolades for his poetic abstract expressionistic style typified in Prismatic Testament and Le Sourie. Claessen began experimenting with abstraction as early as the 1940s, however it was not until he moved to London in 1949, that he fully embraced abstraction. He describes an almost spiritual experience that acted as an epiphany and catalyst towards this abstraction. "I did try to make another dimension - another dimension which I thought had been overlooked and not known in a mathematical sense. I could not however substantiate this as I had quickly forgotten it, in what was a sort of revelatory understanding. But it came in many aspects of my work." (Artist statement, S. Wanigaratne, George Claessen; Artist, Sculptor and Poet 1909-99, London, 2000, p. 24)
"The mind of a true artist is only concerned with abstraction. He is born blind. Artists follow the movement of their own and the world's destiny. Their best work is a manifestation of an outer force which seeks expression through the assembled logic and sensitivity of their minds." (Artist statement, George Claessen; Artist, Sculptor and Poet, p. 29 )
Claessen joined the New Vision Gallery in the 1960s, a group of London based artist committed to abstraction in its many iterations. During this period Claessen developed a unique lyrical language based on the idea of nonrepresentational pre-perception and the sensory experience of the retina.
Ivan Peries said of Claessen, "He is a truly universal artist, a man of vision, of musical harmonies; of temperament so rare and tender: rarely tragic; full of hope and a 'fool' who in persisting in his folly has become a wise man." (I. Peries quoted, George Claessen; Artist, Sculptor and Poet, p. 29)