[1] In the process of obtaining a degree at McMaster University in Hamilton which he finished in 1973, he took courses in fine art from instructor George Wallace who was enthusiastic about German Expressionism.
[2] Hartman has said that the artists who inspired him include figures from art history such as J. M. W. Turner, Albrecht Altdorfer, Chaïm Soutine, Oskar Kokoschka and in Canada, David Milne and the Group of Seven, among others.
[2] In 2007, he said: One of the things which astonished me was realizing the ways in which my Western civilization tended to regard itself as separate from the land, when it would have been much healthier to have conceived of the world as the Aboriginals do – as a huge and constantly changing organism and ourselves as part of it.
He has been called an artist who, in the "true tradition of Canadian painters, is not afraid of visiting the far-flung edges of this country, pursuing subjects, painting them in his edgy style".
Although Hartman has a lengthy exhibition history beginning with a solo exhibition at Trinity College, University of Toronto, in 1972, and with many shows nationally and internationally, largely in the 1980s,[5] it took Painting the Bay: Recent Work by John Hartman at the McMichael Canadian Art Collection in 1993, large-scale paintings of Georgian Bay, aerial views of thickly-painted landscape, to bring him to critical attention.