He was a flatterer and he knew it, and after a spectacularly successful and lucrative career as a society portraitist, he decided to step away from this bread-and-butter business and try to make his mark in a genre that he thought would bring him a more elevated kind of fame.

Accordingly, in 1890 he accepted a commission to create a mural at the top of the main staircase of the newly built Boston Public Library (BPL). The subject was to be Sargent's own choice. His original idea was to depict scenes from Spanish literature, but after giving the matter further thought, he decided to create a series of scenes called The Triumph of Religion that he based largely on the Bible.

Sargent worked on the mural for the next 30 years and never quite finished it. A key panel depicting the "Sermon on the Mount" was never completed. But the bulk of this monumental work, which was painted in Sargent's studio in London then shipped across the Atlantic and mounted in its final location, can still be seen today.

It is looking better these days after being given a surface cleaning by Harvard's Straus Center for Conservation. The Center has also examined the work in preparation for possible further restoration.

For a behind-the-scenes look into the making of this ambitious work and others visit "Sargent in the Studio: Drawings, Sketchbooks, and Oil Sketches" at the Fogg Museum, June 10-Sept. 5.

"Harvard has a huge collection of Sargent's drawings and oil sketches," said Miriam Stewart, assistant curator of drawings. Stewart organized the exhibition along with research assistant Kerry Schauber.

"After Sargent died, his two sisters instructed the executor of his estate to distribute these less-finished pieces to university museums in the Northeast. Harvard ended up with the biggest batch of them."

In the Straus Gallery, where the Sargent show is installed, materials relating to the BPL mural occupy the entire back wall. There are portraits of men in biblical headdress, drawings of architectural details, and oil studies for such subjects as The Fall of Gog and Magog, and Frieze of the Prophets.

Though much smaller than their final size, these are still large paintings, full of drama and movement. Sargent actually built a one-third scale model of the BPL gallery in his London studio so he could plan the relationship of one panel to another and see the effect of the whole.

Hanging over the entrance to the exhibition is a mock-up for one of the mural's most impressive sections, a large lunette connected to a rectangular frieze, both painted on wood, and a plaster crucifix that overlays the two. Getting it ready for exhibition drew upon the full resources of the Conservation Center. "It's sort of a homely object," Stewart said, "but very interesting."

Also in the exhibition are preparatory sketches for other mural projects: a series of murals on mythological subjects which adorn the rotunda of the Boston Museum of Fine Arts and have recently undergone extensive conservation, restoring their neoclassic charms to pristine condition; and the two Widener Library murals, Death and Victory and The Coming of the Americans, commissioned by President Abbott Lawrence Lowell to memorialize Harvard's sacrifices in World War I. Lowell and Sargent collaborated on the verses that appear below the murals.

Although Widener Library is not open to the general public, visitors to the Fogg Museum will be able to obtain a special pass that will enable them to view the Widener murals.

In addition to providing a fascinating glimpse into the thinking and planning that went into Sargent's murals, the Fogg exhibition also provides an equally intriguing look at the artist's approach to portraiture, figure painting, and landscape. In this respect, it is the perfect complement to the Museum of Fine Arts' show of Sargent's easel paintings, "John Singer Sargent" (June 27-Sept. 26), and "Sargent: The Late Landscapes" at the Isabella Stewart Gardner Museum (May 21-Sept. 26).

The son of wealthy, peripatetic, expatriate Americans, Sargent spent his youth traveling around Europe with his parents and recording his observations in a series of sketchbooks.

"You can trace the family's movements through Sargent's early sketchbooks," Stewart said. "It's clear that they were following Baedeker and other popular guidebooks of the time and stopping to gaze at the views that were recommended as being particularly picturesque."

Sargent's mother, an amateur artist, was his first teacher, and it was clear early on that the young Sargent possessed great natural facility. Pencil sketches of cows, goats, chickens, rocks, vegetation, and human figures done at the age of 14 show an extraordinary ability to portray form and movement, light and shadow in a naturalistic style. An early watercolor of an Alpine scene shows his mastery of the difficult subject of ice and snow.

"He had a never tiring eye," Stewart said. "His sketches show an almost obsessive concern with detail. Many of the things he observes on his travels will turn up in his later paintings."

Sargent's oil portrait of Madame Gautreau, titled Madame X, is one of the world's best known visual images. In the Fogg show there are two sketches of the famous French beauty (actually born in New Orleans), focusing like the painting on her imperious profile and bare shoulders.

"Sargent made more sketches of her than anyone else," said Schauber. "He was hung up on her visually. He even drew her profile from memory decades later."

A group of nudes and portraits in charcoal show Sargent's ability to draw the human figure powerfully and dramatically and to fully exploit the expressive properties of this simple medium.

To enhance the sense of bringing the viewer into the intimacy of the artist's studio, the exhibition even includes Sargent's actual paints and brushes. A palette, still thickly encrusted with dried paint, hangs on the wall next to a photograph of the artist in his studio.

During the next few months, an unprecedented number of finished works by this versatile artist will be on display in the Boston area. The Fogg exhibition of the artist's less polished productions adds a further dimension to this unique "Summer of Sargent."