Sadamasa Motonaga was a self-taught artist who joined the Gutai Art Association in 1955, one year after its formation. He participated in all Gutai exhibitions until 1971. Early in his career, with little money to invest in materials, he experimented with inexpensive, non-art mediums and found objects such as wood, rocks, water, plastics, and nails. In 1954 he started to depict cartoon-like forms in dense oil paint, but by 1957 he was experimenting with pouring and dripping bright pigments onto canvas, allowing the colours to mingle.
For another work with a similar application of pebbles to create a three-dimensional effect, titled Work No.501, 1963, in the collection of The National Museum of Modern Art, Kyoto, go to: http:/search.artmuseums.go.jp/search_e/records.php?sakuhin=15654