Born in 1909 Claessen spent his first thirty eight years of his life in Ceylon (Sri Lanka). He belonged to a family who had a strong inclination towards visual arts. He began to paint only at the age of 29 after he joined the Port Commission in Colombo as a Draughtsman.
A founding member of the 43 group, Claessen, came to public notice through the publication in 1946 ‘Jataka’ a little book of drawings by him, which was edited by Ian Goonetileke. Arther van Langenberd provided the Foreword in which he stated ‘The appreciation of a drawing after the first sensation is past, creates a longing for serener, more lasting qualities which the artist is called upon to satisfy. The drawings of George Claessen possess these qualities” (Weereratne, 1993,59).