OF ALL the works in the Museum of Fine Arts's excellent show last spring, "Abstractionists of the Seventies," the two or three most striking canvases were those of Jules Olitski. Olitski's particular combination of richness and control has given him an attraction which blander formalists or more effusive color-fielders both possess only half-way. He is at the height of prominence now, and the show of some 60 works at the MFA shows how and why he got there.

Returning from last spring's show to the current exhibit, a painting called Eighth Loosha typifies the best in Olitski's work. The canvas is a large rectangle, slightly higher than it is wide. In its center is an area of rich purple, built up from layers of sprayed acrylic. Where the surface is thin, the painting opens out around the separate flecks of paint; where the surface is thick, it fuses into a shiny surface priced by bubbles. Toward the edges, the color field lightens and meets a series of linear strokes of color that bound and direct it. On the right the general tone of the painting grows green; there the bordering strokes are green on white. On the left, a plunging red streak ignites the entire canvas like a flare thrown across the night. (I describe the painting in such detail because it is impossible to convey any good idea of the painting in black and white reproduction -- that is the cost of successfully merging color and form.)

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TO PAINT a picture like this required Olitski to paint his way through years of difficulty. The earliest paintings included in the show are a whole room full of small works which look like abstract expressionist paintings, but were executed by building up the surface as much as three inches with spackle. The effect is that of stale cake frosting, limited to three colors -- charcoal, sickly pink, and dirty white -- knifed or squeezed onto the canvas. The paintings suggest parody of the rough, sculptural brush work of De Kooning, at the same time evidencing an interest in the ease with which forms advance from the canvas as well as recede into it. Considered alone, the paintings are hardly promising.

These works, executed during the fifties are followed by a totally different type of canvases, stained with multiple circles and enclosing arcs. The colors are simple, usually those of unmixed acrylics on raw canvas. Resemblances to the work of Gottlieb and Louis are clear.

Olitski's "break-through" -- the sudden leap from mediocre early work so characteristic of modern painting -- occurs in 1964 with paintings like Deep Drag. Here Olitski turns to a rectilinear ordering of the forms: the circles are still there, but they have been driven to the edges where they interact with long, brushed forms to shape out a composition clearly accepting the limits of the frame. (Eventually those circles will be reduced to thumbprints on the smooth field, and finally can be observed as mere drops.) Olitski's characteristic banishment of all drawing to the edges of the canvas appears soon afterward, in paintings like Tin Lizzy Green, but comes into its real success only in 1965 after Olitski begins to apply the paint with spray guns.

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IN THE "MATURE" works -- from the late sixties to date -- Olitski creates paintings that are models of what a good abstract painting should be. The problem of uniting form and content, honesty and illusion is made almost symbolically explicit by the use of the inner color field and its surrounding borders. Each of those elements, in turn, has both a formal and a sensual function. The formal solution of drawing at the edge of the canvas satisfies a felt need to reflect the frame in the structure of the painting, but also allows old style, "painterly" handling to survive. (The styles of some of Olitski's edges can be read as homages to the paint handling of Hans Hofmann or Clyfford Still.)

The color field emphasizes the flatness which is a formal condition of painting, but does so while at the same time allowing itself to be interpreted as infinite depth in the same way as Pollock's canvases, and employing the most romantic and expressive of colors.

The sign that Olitski preserves "sensuousness" in painting is the feeling that we are free to like or dislike the paintings on subjective grounds: the paintings are about color combinations which, with all their attendant moods and meanings, we either enjoy or don't.

When Olitski fails, it is by slipping off into one of the surrounding extremes. Pink Alert, the painting that stands at the entrance to the exhibit, demonstrates the original ideas executed at their best, with the edging strokes well defined, scaled and composed, and the gradation of the color field maintaining a lush, breathing "all-over-ness." But when the borders are reduced to chalk lines in the outer inch of the painting, they tend to slide down into the narrow recess between canvas and metal frame, and let the color field dissipate back into a flat canvas flatly painted instead of the ambiguous thing we recognize as a painting.

At the other extreme, the danger is more complex: that the color surface will grow streaky or wavy and start asserting forms of its own in defiance of the edges. This occurs particularly in the earlier sprayed canvases, when the field begins to look like a random set of tones instead of a unified surface in controlled transition. Danger here also takes the form of boring all-over-ness in a few paintings where Olitski attempts to place one plane of color on top of another, binding the second plane into the picture by making it recede on one side and advance on the other. And then there is the tendency of the paintings to turn into portraits of deep space, flecked with stars (the science fiction-y titles don't help with this) or into late Turner sunsets.

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THE OUTSTANDING thing is that, treading his course between all these dangers, Olitski manages to avoid most of them in about a third of the paintings. In an art of such delicacy, that is many more than it seems.

In addition, he conquers many of the problems of scale which have bothered some other abstractionists, particularly Kenneth Noland. Abstract pictures have usually been able to be successful only on enormous canvases; Olitski works equally well in room-sized paintings and in small ones. His spray technique has a finer grain, so to speak, than staining or brushing, and it creates surfaces which because they cover the canvas completely are not immediately scaled by the weave of the cloth. And in his paintings of this year and last, particularly the Other Flesh series, he employs rollers and sponges with a syrupy acrylic, using the edges built up by rolled paint to create a repeated width across the canvas. These paintings use the rolled edge as internal drawing, uniting form and field, or establish a new kind of painterliness in a surface teased into roughness with sponge or cloth.

At 51, Olitski is clearly still exploring the ideas with which he has had such success so far, and his work promises further advances in a form -- the easel painting -- which since the century began has continually been being saved from the edge of apparent extinction.