Windows are an invitation to look, and Wyeth’s windows are enticing. The National Gallery of Art in Washington, D.C. exploits this very human impulse to look through a window in the exhibition, “Andrew Wyeth: Looking Out, Looking In,” which opens on Monday. It explores sixty of Wyeth’s tempera paintings, watercolors and drawings.

According to his son Nicholas, Wyeth was fascinated by windows. For centuries, artists from Vermeer to Matisse and Hockney have pictured windows as sources of light, as frames, or as focal points in themselves. What is surprising is that Wyeth made more than 300 of these images, all of them windows with no human figures.

When the tempera painting, “Wind from the Sea” (1947), entered the collection of the National Gallery in 2009, curator Nancy Anderson made what she thought was a simple inquiry—whether Wyeth painted other windows. It was the beginning of her exploration of Wyeth’s painting processes. This painting was made at the Maine farm of Christina Olson, the woman pictured in Wyeth’s famous painting, “Christina’s World,” and her brother Alvaro.

“Wind from the Sea” is horizontal and almost photographic. It views the open window at an angle, cropping the right side of the window frame and putting the window sill on a diagonal. Across the top, the shade reveals its age with rips and holes allowing points of light through its dark surface. Outside, a lonely field edged by trees is cut through by a narrow dirt road. From the top, the lace curtains billow inside the room, softening the window’s sharp edges. Among the tiny threads of lace are images of flowers and flying birds. All of the carefully detailed elements describe what is unseeable—the soft summer breeze.

Most exhibitions leave one wondering how such an image came to be. This time the viewer gets to look over the artist’s shoulder. Accompanying the painting are the sketches and watercolor studies Wyeth made in preparation for the tempera composition.

The story goes that one hot August day, Wyeth was in a bedroom on the unused third floor of the Olson farmhouse near the Maine coastline. He opened a window, and when the breeze gently lifted the lace curtains, he quickly sketched the scene. In his haste to catch the movement, he accidentally grabbed a piece of paper that already had a drawing. His first impression of the window, sketched on top of a drawing of Christina Olson, is hung beside the finished painting.

He returned to the window on other days to examine the window frame and details in the lace. Nearby watercolors reveal his progress as he distilled the pictorial elements, using them as a frame for the window’s openness. This “boiling down” as he called it, is evident in all the paintings.

An entire section of the exhibition is devoted to scenes of Wyeth’s studio, a former schoolhouse, in Chadds Ford, Pennsylvania, but even they reveal little. In paintings of the studio’s exterior, the shutters are closed or only half-open. The glass in the open windows reflect nearby foliage, disclosing nothing of the inside.

Views from inside the studio focus on the wide window sill holding toy soldiers Wyeth played with as a child or frost-bitten apples. Neither the small items nor the window itself are the focal point, but the strong sunlight and the deep shadows it creates. Wyeth’s studio and the nearby Kuerner Farm, featured in many of his paintings, are now part of the Brandywine River Museum of Art and are open for tours.

Of the sixty works on paper in this exhibition, more than half are from private collections, providing a unique opportunity to see paintings usually unavailable to the public. Others, on loan from museums across the country, show the nationwide interest in Wyeth’s work. And ten works on paper are from the Marunuma Art Park Collection, Saitama, Japan, near Tokyo.

Andrew Wyeth: Looking Out, Looking In, on view May 4 through November 30, 2014. National Gallery of Art, Sixth and Constitution Avenue NW, Washington, D.C., (202) 737-4215. http://www.nga.gov/content/ngaweb.html

More information about Ann Saul’s work can be found at pissarrosplaces.com