THIRTY YEARS ago today Helen Frankenthaler invented a new form of painting with color in a work called "Mountains and Sea." This landmark painting gave rise to the Washington Color School.

Although only 21 years old at the time, Frankenthaler had already come to know many of the leading artists of the abstract-expressionist generation. The rapid execution and the intense abstraction of Jackson Pollock's work was an important influence on this then virtually unknown abstract painter from New York.

Frankenthaler had just returned that fall from a painting trip to Nova Scotia. The colors and images of the trip -- the oranges and grays of the rocky landscape and the blues and greens of the Nova Scotian seacoast -- remained vivid in Frankenthaler's mind and worked their way into the abstract picture. "The landscapes were in my arms as I did it," she said in a later interview. "One of the things that struck me," she recently added, "was the unique contrast between the great wooded peaks and the horizontal ocean -- the mountains and the sea of its title."

The manner of painting "Mountains and Sea" was rapid and improvisational. Freidel Dzubas, a painter who shared Frankenthaler's Manhattan studio, remembers that day: "Helen just walked in, painted the picture, and then asked me to come over and look at it." Taking her cue from Pollock, Frankenthaler had made the picture by spreading a big canvas on the floor and pouring paint onto it. But unlike Pollock, she used raw, unsized canvas and paint of such a liquid quality that it soaked into the fabric, rather than sitting on top. To some degree, the soaking quality of her colors must have been an outgrowth of the watercolors she had painted in Nova Scotia. With "Mountains and Sea" Frankenthaler created a method of working with color without physical weight on a very large scale. This was later called "stain painting." The picture is dated 10-26-52 in large numbers. "I usually don't, but I remember wanting to do so with the picture that day," Frankenthaler said recently.

Shortly afterward, two Washington artists, Morris Louis and Kenneth Noland, learned about the painting from Clement Greenberg, a close friend of Frankenthaler's. Louis and Noland had met earlier at the Washington Workshop Center organized by Ida and Leon Berkowitz, and had quickly become good friends. On April 3, they made a special trip to New York to see "Mountains and Sea" in Frankenthaler's studio, accompanied by Greenberg, Franz Kline, and the Berkowitzes.

Louis and Noland were stunned by the painting. Noland recalled: "We were interested in Pollock, but could gain no lead. Frankenthaler showed us a way to think about and use color." Louis called "Mountains and Sea" a "revelation" and said Frankenthaler was "a bridge between Pollock and what was possible."

Returning to Washington, Louis and Noland experimented with the staining technique. Their desire to explore what Frankenthaler had done was so intense that they painted together on the same canvas, in what Noland calls "jam painting, like jam sessions with musicians." After several weeks they returned to their separate work, developing their individual styles. Noland said of the effect of "Mountains and Sea" on his colleague: "It was as if Morris had been waiting all his life for information. Once given the information, he had the ability to make pictures with it." Together with other artists in the city, Louis and Noland went on to found the Washington Color School, and with Frankenthaler and other New York painters they created Color Field painting, the movement that dominated American abstraction in the 1960s.

Morris Louis died in 1962. Helen Frankenthaler and Kenneth Noland remain among our country's most important artists. Frankenthaler continues to be inspired by the seacoast near her Connecticut home. Noland now lives nearby. Both still employ the staining technique Helen Frankenthaler invented 30 years ago today.

Still in the artist's collection, "Mountains and Sea" has been widely reproduced, less often exhibited. In 1975 I asked Helen to make the painting a long-term loan to the National Gallery. It has been on almost constant view since.