Painter, born in Edinburgh, where he studied at the College of Art, 1966–71. Onwin while still a student became interested in salt as a medium to create images, and in 1973 discovered a large salt-marsh near Dunbar which inspired him to create works charting the evolution of nature. Salt was seen as a life-giver and as a destroyer, and Onwin went on to use it and other natural substances to make works which warned of the dangers of industrial pollution. Scottish National Gallery of Modern Art has his three-panel work Salt Room Crystal, of 1977. Onwin’s show Saltmarsh appeared in 1975 at Scottish Arts Council Gallery, Edinburgh, and Serpentine Gallery; other shows included Revenges of Nature, at Fruitmarket Gallery, Edinburgh, and Third Eye Centre, Glasgow, 1988–9, and in 1997 The Quality of Light, The Tate at St Ives.