IT'S COLOUR SHE LOVES

THERE ARE two ways to get to Room 38 at the Tate Gallery, a small, corner chamber where, over the summer and for the next fortnight, four of Gillian Ayres's abstract paintings hang alone, filling the walls with splendid majesty.

Each of the two routes to the Ayres exhibition takes you through a long hall of paintings. The pictures are utterly different, yet each has been carefully chosen to hang beside its neighbour, linked by a coolness that is tonal, reflective, understated. Rothko's dark, magnificent squares, originally designed for the Seagram building in New York, are to be found along one route; works by Paula Rego and Stephen McKenna line the other.

Walking through these galleries, your first thought is one of relief that these paintings have been separated from Ayres's pictures, for although they form a fine selection of English and American painting of the last 40 years, there is something about Gillian Ayres's canvases that obliterates everything that hangs beside them.

The four paintings in Room 38 range from Disintegration, a Pollock-like explosion of fireworks against a blue background that dates back to 1959, to the richly iridescent, almost three-dimensional, Antony and Cleopatra that was painted in 1982, at the start of Ayres's finest period. Out of long habit, Ayres links up with two or three friends, including IoS art critic Tim Hilton, to name her paintings once they're finished. "It's like christening them," she says. The connection between subject and title is not always immediately obvious, as was evident to the buyer who changed the title of one picture from Ariadne on Naxos to Fiesta without telling Ayres. "Cheeky, wasn't it?" she says.

Each painting celebrates the physical act of applying paint -no one can fail to see how painting for Ayres is "action", an intense love affair with the smell, feel and effort of working the pigment. Purple lozenges, orange sticks of barley sugar, yellow Polo mints, bright pink croissants and apricot whirls overflow in an incandescent motion that is so intense John Ruskin might have been thinking of Ayres when he wrote in The Stones of Venice: "The purest and most thoughtful minds are those which love colour the most."

Now 65, Ayres is among our foremost abstract painters. The Royal Academy is planning a retrospective of four decades of her work in early 1997, one of the greatest accolades the British art establishment can offer a living painter.

Ayres is a woman of acute contemporary consciousness, but her preference is, and has been ever since she first went to Camberwell School of Art in 1946 at the age of 16, for the abstract. She never paints portraits or sketches landscapes, not even for relaxation. "Shapes. Spaces. It's the way I see the world," she says. Shapes. Spaces. And, of course, colour.

"TO ME, art - colour in art - is wonderfully indulging," Ayres told me a few days after my visit to the Tate, when I went to see her in her cottage in north Devon. "I don't see why you shouldn't be filling yourself up, making yourself happy. Enjoying yourself. Feasting on beauty. I want an art that's going to make me feel heady, in a high-flown way. I love the idea of that. I'd use the word spiritual. I'm not frightened of all that."

Ayres is not a tall woman, though generously built. When I visited, she was dressed in a rust blouse, black jersey, and trousers that were blue until they were put into an over-exuberant drier and came out with brown streaks. She is also, it would be fair to say, a bit batty. One curator recalls visiting her to choose pictures for an exhibition. As he was making his choice, carrying the canvases out on to the lawn, she would go on working on the paintings. "But then that's often how you do exhibitions when you have a mad artist," he says today.

For all that, Ayres is also beautiful, and unusually, for an English artist, has always revelled in the life of beauty within disorder. Her hair is thick and blonde; her eyes light and full of laughter. And her fingers are covered in rings; a mountain of moonstones, a flat dark oval, a large green square mounted in silver.

She never stops talking. Partly she does it to hide a certain shyness, partly out of exuberance at the sheer joy of it. And she isn't afraid of expressing unfashionable sentiments, proclaiming a love of beauty and a search through it for truth and life. "I like Matisse very much, and all Venetian painting. I remember the books at school of Van Gogh and Gauguin, and I remember thinking, `Wow, this is what painting can do'.

"All the painting I've liked has always been colour painting. I've found that I respond to colour more than anything. Do you know that every artist has their own colour? If I name artists, I start spinning out their colour in my mind. If I think of Matisse, I'm going to think of red or emerald green. I'm going to think of those pinks and lemon yellows. But if you said Kandinsky, I'm going to think of more beetroot red and yellows. And if you said Pollock, I'd say black and white. Black and white can certainly be colour too."

Just getting to Ayres's cottage is a journey through a feast of colour. A mile or so before we arrive, we reach a land that begins to snake its way to the sea. The foliage, even in early autumn, is so thick it forms a canopy above us, a tunnel of green that spills over in a blend of apple, sage, mint, and a pine green that is nearly black with splashes of white where the sun peeks through. Cross a stream, open a gate and we are there.

Pink flowers spill out over a small car park. There are lines of white on the concrete where Ayres has laid out her enormous canvases for priming. Smoke rises from the chimney. Hens peck at the flower beds, and her four collies spill through the garden in splashes of white, black and red.

Ayres's husband, the painter Henry Mundy, whom she divorced in 1976 yet lives with once more, comes out to greet us. In the early Sixties, Mundy was one of the best known painters in Britain. Today, only the older generation remembers him. Just how this reversal of roles affects the pair is something Ayres doesn't want to go into. "We are friends. Old, close friends," she says. They both paint every day, in adjoining studios: Mundy's at the back of the house and Ayres's large, airy one at the front, overlooking the garden.

Their two sons, Jimmy, 37, and Sammy, 29 and also a painter, are there too. I feel perhaps that they have come to make sure I am fed and given a towel and fresh sheets. "I'm a terrible housekeeper," Ayres proclaims, with only a touch of embarrassment. "I'm terribly untidy and I never clean up." That evening, the sons and a friend serve dinner in a tiny kitchen that spills out into a conservatory filled with Mundy's splendid tomato and basil plants. A cheque for nearly pounds 30,000 from Gimpel Fils, Ayres's dealer since last May, sits atop a pile of mail. Her paintings cost twice that and sell regularly, proof that after years of financing her work by teaching, Ayres is now free to live only by and for her painting.

Her work is displayed all over the house. Painted plates inhabit the loo, painted tiles hang in the conservatory. Painting is an obsession with Ayres, and she orders her colours not in tubes but in half-litre tins which she leaves, lid off, strewn around her studio in a sluttish array of colour.

Virtually everything we eat that evening has been made, grown at or collected around the cottage. A mushroom pate, a freshly baked loaf of bread nearly as big as a lorry-wheel, bronzed duck with two sauces, spinach, runner beans, parsnips and potatoes cooked together with zest of lime, herbs and olive oil, and a pie of apples and blackberries, all washed down with two bottles of champagne and many more of red Rhone Valley wine. The sons call their parents Gillian and Harry. And even though they have clearly inherited their mother's appetite for life, they worry over her diabetes injections and her incessant smoking of Players Navy Cut. Unfiltered, of course. "Nobody smokes these anymore," she says wistfully. "You're all too young."

IF AYRES'S life today is exactly how she may have chosen it when she first went to art school, it wasn't always so. She was born in south London, and grew up in Barnes, the youngest by far of three sisters. Her father had a factory making expensive hats, and her mother came from a Suffolk farming factory. She went first to the progressive Froebel School in Roehampton, and remembers her parents driving her to Woodstock where she was to be evacuated at the start of the Second World War. "As we went up the drive, my mother, who always gave orders, told my father, who always obeyed, `Drive on, I'm not leaving her here'." Ayres was taken home, and eventually joined a class of five- to 18-year-olds for lessons in an air-raid shelter. Shirley Williams was one of her classmates. Shirley Conran, who bought 15 of Ayres's canvases from her Serpentine Gallery show in 1983, joined them later.

At the end of the war, Ayres went to Camberwell, which was, she says, "totally disappointing" although she made some great friends, including Howard Hodgkin, William Johnstone and Victor Pasmore, whose sister taught her. "Teachers in those days were vote-collectors. It was Euston Road and they formed a school. They were after conversion. I was only 16. But I didn't like it then and I wouldn't like it now."

She left after four years without taking a degree. But she knew right from the start that painting would be her life. "When you're a born artist, it's almost like you're trying to breathe. You can't do anything else."

For a short time, Ayres moved to the West Country in the vague belief that she could be a charlady and a painter at the same time. When that proved too exhausting, she moved back to London where she shared a pounds 5- a-week- job at the AIA Gallery in Lisle Street, then one of the few spaces that would exhibit abstract art. Her partner in the job was Henry Mundy, whom she later married.

In 1957, the architect Michael Greenwood commissioned her to paint an 80ft mural for the dining hall at South Hampstead High School. Without knowing much about American painting, she took inspiration from a celebrated photograph by Hans Namuth of Jackson Pollock painting on the floor. Working on her hands and knees, she produced a lyrical abstraction of monumental scale. The builders were aghast, though impressed by her energy. The same could not be said of the school governors, who eventually had the mural papered over. When finally it was uncovered in 1983, the headmistress wrote to Ayres asking if she minded whether it was sold. Ayres replied: "I was paid pounds 100 for doing the job. You covered it over. Frankly, I don't care what you do with it."

Art-school teaching - at Corsham, St Martin's and Winchester School of Art, where Ayres was head of painting -was her livelihood for more than 20 years from 1959. Throughout the years when expressionist abstraction, and eventually easel painting itself, went out of fashion, she stuck by her work.

One important influence was the abstract painter Roger Hilton, who died in 1975 and whom Ayres met in 1951. Hilton's conviction about abstract expressionism was similar to her own, and he had been the first person to "really" talk to her about painting. During my visit, she showed me something he'd written in 1953. She'd marked it then in pencil, and still refers to it now, four decades later. "The abstract painter submits himself entirely to the unknown ... his only props his colours, his shapes and their space-creating powers. Can he construct with these means a barque capable of carrying not only himself to some further shore, but with the aid of others, a whole flotilla which may be seen eventually as having been carrying humanity forward?"

That belief notwithstanding, Ayres's work for many years retained a cramped quality. Was it the cumu-lative effect of raising children, ill health and so much teaching? Whatever the answer, it wasn't until 1981, when Ayres was sacked from Winchester as a result of cuts in funding, and moved to Wales to a bigger house so she could paint without distraction. Thus began her most creative period. "They heaved me out at a good time. Now I'd say, `Thank you'."

Tim Hilton, who spent three weeks cataloguing and selecting work for Ayres's retrospective at the Serpentine in 1983, remembers visiting her just before the move to Wales. "Her house was totally neglected. You'd have to scrape the kitchen floor. But upstairs there were all these paintings draped all over the furniture. They were free. They were extravagant. That's when she hit her best period."

Ayres moved from Wales in the late 1980s, spurred into action by the growing Welsh nationalism, which offended her sense of individual freedom, and the economic necessity of having to find a smaller house to heat.

Hardly a year has passed since 1956 when she hasn't exhibited somewhere in Britain (an invitation by the British Council in the mid-1980s to paint and exhibit in India led to a rare occasion on which she has worked outside Britain). Later this year, her new dealer, Rene Gimpel will take her work to the Paris Art Fair. He has promised her a solo show next year. And then there's the RA show in 1997.

This support is welcome, and hardly surprising when you realise that, although she proclaims herself disorganised, Ayres still works every day. "I could never start off at a set time, like some artists, then work for three hours, have lunch and then teach in the afternoon. I start whenever. But then I go on until I absolutely can't paint anymore. And sometimes that's for hours and hours."

Painting, for Ayres, is not a job. "She gets twitchy if she can't put pigment on canvas," says Tim Hilton. "And if she can't put it on canvas, she'll put it on something else." As Ayres herself said about her very first paintings way back in 1953, "I was obsessed". She still is.

! Tate, SW1 (0171 887 8727) to 10 Oct.