HOW TIRESOME plastic has become - the safe and shiny sameness that is the look of commerce. The developers of White Flint, the North Bethesda shopping mall which opens Monday, may have found an antidote. It took less cash than courage. They took a chance on art.

White Flint cost $50 million, and one-twentieth of 1 percent of that huge investment was given to a painter, Washington's Gay Glading. "We wanted something special," says developer Ted Lerner of the Lerner Corp. That is what they got. Glading has transformed that shopping center in the suburbs with eye-delighting, spirit-lifting works of public art.

"Sky Light" is their title, and the universe their subject. Glading's towering paintings of the stars, the sun, the heavens, are four stories tall, and there is no gallery in town high enough to hold them.

White Flint is enormous - its 800,000 square feet hold two full-size department stores (Bloomingdales, Lord & Taylor), movie theaters, restaurants, fast food stops, boutiques. And White Flint is ambitious. "No expense was spared."

But almost everywhere one looks one sees the familiar - gleaming chrome, gleaming glass, formica, tile, copper - surfaces produced by machines and not by hand. You have seen that shine before, that hard harsh light of commerce; but the banners of Gay Glading cast a different sort of glow.

They humanize, they soften the hardness that surrounds them. They do so much so well that one begins to wonder: In developments so costly why in the hand so seldom seen? In surroundings so familiar why are works of art so rare?

To blame the absence of art on the philistines, on cost-conscious businessmen, is to miss the point. Developers spend millions on "visual amenities" - birdcages and fountains, elevators sheathed in glass, decorator colors. That high gloss can be purchased in every city of the country. Art strong enough to fight it is in short supply.

Most painters and most sculptors are content to serve a tiny knowing audience of show their work in tiny white-walled galleries. They will not take the risk of showing in the market place.

There are, of course, exceptions. One is Rockne Krebs, whose sunlight-powered rainbows and laser sculptures drift through the Omni in Atlanta. Another is Glading.

Though she rarely shows in small commercial galleries - where exhibits that draw as many as a hundred viewers a day are considered his attractions - her work is seen by millions. More than 5 million viewers have seen Glading's "Venus" at the Air and Space Museum. Before the year is out, more than 10 million more will look upon the banners she has painted for White Flint.

Glading is 37. Like other Washington color painters, she used to place her work within the confines of the art world. Then she broke its bounds, and started making works of art that could be used and worn. You may have seen her shoulder bags of embroidered and hand-painted canvas. Each one was assembled of small paintings, a painting on the front, another on the back, a third upon the strap. Then she painted visors, she must have made a thousand, each one with a painting of a landscape or a monument, an abstraction or a still life. She used to be an abstract painter, but then she studied Leonardo, the Chinese and Cezanne, and taught herself to draw. She painted and she painted. All Gladings look like Gladings. No artist in this city has made so many paintings in so many different styles for an audience so wide.

Six of her huge banners are hanging at White Flint. Though unified by theme - they have a kind of space-age plot - all of them are different. Their imagery is drawn from photographs of spectra, from portraits of the sun, from the hexagrams contained in the Chinese Book of Changes, and from the sky at twilight. Suspended there, in sequence, from the sky lights at White Flint, her paintings lead the strolling shopper who exits Lord & Taylor from the fringes of the universe, through the milky way, past the glowing sun, through earthly clouds at twilight, into Bloomingdale's door.

Glading's White Flint banners were painted in a basement on Columbia Road NW. Because they are large - four are 42 feet long, two are slightly shorter, all are painted on both sides - Glading did not see them in entirety before they were installed. Like color painter Morris Louis, whose infuried canvases were larger than the little room in which he made them, Glading made her paintings one section at a time.

She used a wooden frame with yards of canvas upon rollers, a scroll device constructed by her brother-in-law and invented by her father. At any given moment, the device presented to her spray gun a rectangle of canvas 4 feet wide and 6 feet high. When that panel had been painted, the canvas was rolled up until another 6-by-4 feet sone replaced it. Before the banners were completed, Glading painted pictures of that size more than 60 times.

"'Sky Light,'" says Gay Glading, "involved a giant jump in scale. I must have made 400 visors, each no bigger than my hand. Then suddenly I was painting canvases so large I couldn't see them. I painted 1,640 square feet of canvas for White Flint. That's like a strip of shoulder bags that runs up one side of the Washington Monument, down another side, and to the top again."

Glading, in the past, has struggled for a living. "It is really scary to be a single woman, approaching middle age, with $10 in the bank," she says. The Lerner Corp. paid her $24,000 for the banners at White Flint. With that money Glading purchased her materials, constructed her "device," rented her basement studio, and hired Dorothy Jackson, a most practical assistant, "I couldn't have done it without Dorothy," she say.

It was her public works of art, those in real life, that earned Glading her commission for the banners at White Flint.

"Luis Lastra of the Pyramid Galleries suggested Glading's name," says Sam Morrow, the Washington designer who did the interiors at the shopping mall. "I'd never heard her name. So I went down to the Air and Space Museum and spent an afternoon watching how the public reacted to her Venus. That picture is amazing. It has a mesmeric quality. You should see how people young and old react to that space painting. They try to reach into it. I figured Glading was the painter we should hire for White Flint."

Four of the banners, the long ones, the ones in softer blues and greens, hang from skylights in the light wells that connect the shopping mall's three floors. The other two, perhaps the most beautiful, "Pathway" and the "Sun," hang from opaque ceilings. "Where I had the sun to work with, I used the light it gave me. Where I had no daylight, I tried to paint two pictures that cast light by themselves."