[10] His first solo exhibition was at the Argus Gallery in Melbourne, Australia and four years later in 1969 he won the Manawatu Prize for Contemporary Art with Modular 10 Series 1, 1969.
[11] In 1971 Thorburn was selected to represent New Zealand at the XI International São Paulo Art Biennale in Brazil, along with Ralph Hotere and Michael Eaton.
[14] After art school Thorburn initially worked with landscape forms often adding relief elements to the surface, but around 1967, he extended these ideas to shaped canvases that could descend down the wall to the floor.
"[19] Reviewing Thorburn’s contribution to the 1971 São Paulo Biennale, art historian Patrick Hutchings wrote how his paintings had become, "aesthetic machines.
The tight modular paintings gave way to image-based work incorporating "leaves from the 1982 calendar and holographs of pages from his PhD thesis".
Art writer John Roberts put the change down to Thorburn's living in New York City with its graffiti covered trains resulting in a, "preoccupation with calligraphy.
"[23] While travelling on a Queen Elizabeth II Arts Council grant in 1971, Thorburn met Len Lye in New York City.
The interview was one of a series Thorburn conducted with New York artists[26] in preparation for his master's degree from Ohio State University.