SANDRA BLOW’S large, bold collage pictures have an immediacy that belies her method of working. They are not, as one might suppose, the inspiration of a moment but the result of painstaking experimentation. Blow temporarily stapled pieces of coloured paper or other material to canvas, wood, board or paper, and altered positions, shapes and colours until the final overall composition of a picture suggested itself. “I wait for the picture to talk to me — to tell me what it wants,” was how she put it. And it was not until the picture cleared its throat that she would reach for her paintbrush to work around whichever of the appended items she retained.

Collage featured regularly in her work from the mid-1950s right into this century, with “found” articles such as sacking, plaster or grit giving extra dramatic texture and focus to her confidently asymmetric agglomerations of interrelated colours and shapes.

Blow was born in 1925 in London, but her parents owned a farm in Kent, and, when she was a child, agriculture was one of the careers that appealed to her. There was certainly no thought of art school until she was 14 and an impressed family friend raised the possibility. Clearly, this must have spoken to some unconscious inclination because it was only a few months before the 15-year-old Blow enrolled at St Martin’s School of Art in London, one of its youngest students ever, for five years of what she later called “paradise”.

She loved it all — the work, the company of other artists, going to all the wartime exhibitions and enjoying a close rapport with her tutor, the painter Ruskin Spear, whose habitual two words of encouragement for most of her efforts — “Bloody good!” — were praise indeed.

From St Martin’s, Blow went first to the Royal Academy Schools and then to the Accademia di Belle Arti, in Rome. It was in Italy that, at the age of 22, she met the artist Alberto Burri, ten years her senior. With him she travelled Italy, both of them painting pictures and seeing as much as they could of other people’s work (always to be a fascination for Blow). Burri was on the brink of breaking into abstract art himself, and introduced her gently to the subject (of which she had hitherto seen only hints at a Picasso exhibition in London), debating with her the relationship of forms and spaces in Renaissance paintings, which clearly had resonances in the world of abstract art.

Blow also met and talked at length with the American abstract artist Nicolas Carone, who had a studio next to Burri’s. A figurative artist herself up to this point, she returned to Britain in 1949 determined upon a new direction. Searching for abstract forms that would express something within herself was, however, a long process of trial and error.

She staged her first exhibitions at Gimpel Fils, in London, in 1952 and 1954, and, although her work sold right from the beginning, she was far from happy with her efforts. Trying to relate her pictures to particular ideas, themes or lines of poetry had resulted in “some rather odd paintings”, she said 50 years later, adding: “I remember the effort and, well, almost the agony of producing them. I am not sure how much I would like them now.” But, by 1956, she had borrowed the idea of collage from Burri, and, using a variety of found materials, in particular sacking, she was on surer ground.

The fixing of the found materials was a starting point from which her investigation of spatial relationships could conveniently take off, and these early collages were the first of her pictures that she was still to value years later. She included her Cornwall of 1958, for instance, in her 2001-02 exhibition Space and Matter, at Tate, St Ives, its use of sacking and plaster giving an extra, bold dimension to its evocative sandy, earthy and terracotta shades.

Soon, she was attracting glittering prizes, winning the British section of the International Guggenheim Award in 1960 and, the following year, the valuable second prize in John Moore’s Liverpool Exhibition awards.

This was a period when, after her earlier uncertainty, she was at long last confident enough in her work to consider devoting some time to marriage and parenthood. But, by 1960, she was already in her mid-thirties. “And I think I must have looked as if I wanted children and put all the men off,” she chuckled years later, retaining a sense of proportion about the disappointment.

The South Kensington studio she acquired in 1960 (unusually large for central London at 17ft high, 35ft long and 27ft wide) had an immediate influence on her work as she found it impossible to paint small pictures there. At the same time, she was finding herself thrilled by the huge abstract paintings being produced by American artists, and was beginning to regard her own larger, and sparer, pictures as being her definitive work.

Typical of these pieces was her Green and White — nearly 10ft square — which was bought by the Tate in 1969. The simplicity of its strips of white and beige against two tones of green spoke mostly of spatial relationships, but the Queen Mother’s less complicated reaction to it — “I’ve always liked green” — gave the artist as much pleasure as any.

To a convivial, good-hearted woman such as Blow, who was as interested in other people’s work as in her own, the years 1960 to 1975, spent as a tutor at the Royal College of Art, were a joy, particularly as her old friend Spear was also on the staff, and for part of the time the students included David Hockney and R. B. Kitaj. In 1983 she was made an honorary Fellow of the college.

Bouts of illness — a heart operation in 1970 and recurring heart trouble with pulmonary fibrosis in the late Nineties — lay ahead. But so did what were arguably her finest works: her majestic pieces of the late 1980s and early 1990s, collage pictures such as Vivace (1988) and Glad Ocean (1989), great washes of urgently applied colour on pale grounds, their drama punctuated by vivid, multicoloured little splinters of paint and collage.

Nature’s textures and dynamics were always an influence for Blow, and, painting in Cornwall in 1957-58, and again when she returned there to live in 1994, she ensured that the strength of her pictures lived up to the vigour of the landscape or seascape around them. Her Cornish pictures took on a fresh quality of light together with engagingly oblique references to sand and sea.

Over a career of more than half a century her works found homes as diverse as the V&A in London, the Museum of Modern Art in New York and the Middle Eastern departures lounge at Heathrow Airport. Into her mid-seventies she was producing innovative, arresting and exuberant canvases for exhibition, rising every morning with the all-important light and painting almost daily. Her model, she said, was Chagall, and she was haunted happily by a picture of his, painted when he was 94, which she had seen in an exhibition at the Royal Academy in 1985. “It was a real picture, a proper painting, not an old man’s doddery this or that. I was amazed that, at that age, he had that power,” she said.

Chagall never wanted to retire. Nor did she. At 76, she tirelessly created new work, despite ill-health and building work that kept her out of the only studio large enough for her massive canvases until three months before a major exhibition opened.

She was unmarried.

Sandra Blow, artist, was born on September 14, 1925. She died on August 22, 2006, aged 80.