John the Painter, a psychiatric patient, has been painting on bed sheets and cardboard for years. Now IMMA is mounting a show of his work. Kathy Scott reports on John's story and on 'outsider' art

There was a sense of ceremony and ritual about the unwrapping last week of the art of John the Painter, on the floor of the chapel at the Royal Hospital Kilmainham, the Irish Museum of Modern Art's Dublin headquarters. The stained-glass windows cast shafts of winter sunshine across the vivid canvases - although canvas is not an accurate word, as this vibrant work is mainly brought to life on cardboard, bed sheets, print paper and any recycled material that John could get access to in the psychiatric hospital where he lives.

Catherine Marshall, senior curator and head of collections at IMMA, who decided to exhibit John's work, points out that his confident approach to composition and colour is envied by mainstream artists who have seen his work. IMMA would have been hungry to exhibit John's work regardless of his outsider status. "In my opinion, John is one of the most important artists to emerge from this country in the last century," she says.

John was a patient in psychiatric care at Our Lady's Hospital in Shanakiel, Cork, when his work was discovered and encouraged by Sheila Holland, a therapist at the hospital, and by Cork Community Art Link, under William Frode de la Foret. It is a reflection of the shift in attitudes that such an artist should have an exhibition at IMMA.

Outsider art has sparked controversy and debate because of its anticultural stance and refusal to be categorised. It is essentially spontaneous, outside of tradition and removed from social and cultural conditioning.

The approach has been described as the underbelly of modern art and a key ingredient in understanding creativity outside of the gallery system.

The exhibition at IMMA pays tribute to John the Painter as one of Ireland's most important outsider artists, celebrating the story of a man who, after 30 years in psychiatric care, may be regarded as a significant painter.

He became known as John the Painter partly for reasons of privacy and partly, and more importantly, because of his ability to express himself so skilfully and individually through painting.

Now in his 50s, John has been painting for the past 10 years, always with gusto and vitality. He is willing to comment on his work when drawn but is more at home with the process than with its interpretation.

When you see his work for the first time it is extremely uplifting, especially as it comes from a patient who had been living in psychiatric care for such a long time. Although John is aware of the exhibition, it is his friends at Cork Community Art Link and the staff of the gallery who seem most excited.

Marshall says: "People have been worrying that, throughout the second half of the 20th century, painting was dead and new-media photography and performance have relegated painting to the scrap heap.

"When you see this work, you realise that painting is as vital as ever. What is also remarkable is that without being familiar with any of the great movements of the 20th century and without any training at all, John uses techniques that have been used already by other big figures in 20th-century art.

"He did a few drip paintings like Jackson Pollock, he spreads dots around in a style similar to Penke, I see bits of Irish expressionist artists that I know here, such as Mick Cullen, that John that might have affinities with, but he has never seen anything by Mick Cullen in his life."

It is this ability of the outsider to draw on the subconscious with immediacy and individuality that presents such a challenge to critics, collectors and commentators. John approaches painting simply, reassembling his experiences of growing up in Cork.

There are images and visual motifs from the 1950s and 1960s, from Elvis and Johnny Cash to Catholic iconography. A sense of Cork city is also prevalent, from the Father Mathew statueand Father Manley clock to St Fin Barre's Cathedral, Murphy's and the Savoy (where he saw The Rolling Stones). Much of his work is autobiographical; his late work is also celebratory, as his self-expression takes a more abstract form, vividly concentrating on colour.

Marshall is keen to point out the uplifting nature of his work. "John has a strong instinctive sense of what will work, an unerring sense of colour, whether working figuratively or abstractly. Some outsider work is very sombre and deeply depressing. John's work is always very exultant and exuberant.

"I think John the Painter is a real artist in his own right and, given the chance at all, he would do this all the time. He has a remarkable drive and his work has a very strong sense of a unique and individual personality."

IMMA is no stranger to outsider art, having brought the Musgrave Kinley Outsider Art Collection to Ireland in 1998; it has since been donated permanently.

The term outsider art was coined in 1972 by the art critic Roger Cardinal as an indirect translation of art brut, the name given to the work collected by the French artist Jean Dubuffet in the 1940s.

Dubuffet found creative expression on the streets, among the dispossessed, in the asylums and from those who considered themselves to be outside the mainstream of society.

He attacked bourgeois culture by highlighting the spontaneous drive and aesthetically isolated approach to art found among children, the self-taught and the psychotic. The compulsive freedom of expression apparent in the work prompted debate and attracted the attention of surrealist artists and writers.

In the wake of Dubuffet's ideas, the poet and filmmaker Victor Musgrave and his partner, the curator and art dealer Monika Kinley, began to assemble their own collection. In 1979, they launched the Outsiders exhibition at the Hayward Gallery in London. The controversial show split the art world in two. Critics hated it but the public queued for hours to see a collection that embraces individuality, from the visionary to the art of the insane.

When this international collection opened at IMMA, the search to document and collect Irish outsider art was already afoot. It is difficult to find and catalogue, as it usually comes from outside established art circles, made in secret or within the confines of institutions. It is often spotted by artists who act as catalysts and encourage the work.

Art produced by the institutionalised has always held a fascination for both connoisseurs and psychiatrists. The art therapy embraced in the 1960s by psychiatrics such as RD Laing was regarded as both therapeutic for the patient and resourceful material for psychoanalysis, but it did not put a huge aesthetic value on the art produced in the process.

There is a striking difference between art therapy and the art created by Dubuffet's outsiders. In the more relaxed art studio or workshop, which concentrates on the artistic process rather than the therapeutic outcome, the artist is able to shine. In the Artists' House in Gugging, Austria, for example, patients are stimulated to make imagery not for therapy but to enhance their lives.

This progressive approach is mirrored at La Tinaia, in Florence, and at the Living Museum in New York, where abandoned hospital units have been transformed into internationally recognised art institutions.

Cork Community Art Link initiated a similar approach at Our Lady's in the early 1990s. Frode de la Foret, a French artist who works for the group, is dedicated to building the self-confidence and social skills of the patients with the vision and support of Holland.

The art programme led by Frode de la Foret has always been interactive, with patients encouraged to develop their own studio space; he built an atmospheric workspace with beach pebbles, sand and a thatched cottage.

Unfortunately, the workspace has been abandoned and the project discontinued because the hospital unit was closed and the patients relocated. John the Painter has therefore had no facilities to paint for the past two years.

He stresses that the social nature of the art programme provides an outlet for creative energy regardless of the end product. "This was the first point of contact with the outside that some of the patients had experienced for years," he says. "Initially, the programme was about resocialisation and communication, interaction between previously separated men and women and lots of cups of tea."

This is the environment from which John the Painter emerged. Although his first paintings were inhibited, as John grew more confident he began to paint on large canvases, measuring 14ft by 6ft, with an eye for colour and confident brush strokes.

"We worked in a bare room with little materials and equipment, but on one particular morning I introduced John to painting on a larger scale and he has never looked back," says Frode de la Foret.

"He does not stop to wipe or clean his brushes, and mixes one colour into the other continually, but he works on this scale with complete fluidity. There is a definite symmetry to his work, where every gesture is calling for another one afterwards. He has developed a system where everything has its place, a distinct sense of order."

The role of the facilitator is crucial. With John the Painter, Frode de la Foret was a driving force, and the men have become friends. But he is disappointed by the level of access to and participation in the arts in Ireland. Since the space at Our Lady's closed, Cork Community Art Link has been in urgent need of premises. Although it is still committed to access and participation, it is surviving on basic project funding, with no ongoing commitment, from the Arts Council.

It is ironic that as IMMA celebrates the work of John the Painter and honours him as an outsider, the framework that has supported his creativity has come to a standstill due to lack of funding for Cork Community Art Link and the closure of the hospital unit. IMMA's decision to straddle the worlds of mainstream artists and outsiders reflects a progressiveness absent elsewhere.

• John the Painter's work is at the Irish Museum of Modern Art, Kilmainham, Dublin, until June 8th. The gallery is open 10 a.m.-5.30 p.m., Tuesday-Saturday, and noon-5.30 p.m. on Sundays and bank holidays

• Kathy Scott is making a documentary about outsider art in Ireland