Pastels are only rarely exhibited due to the fragility of the powdery pigment and the light sensitivity of the paper on which it rests. Drawn primarily from the MFA’s holdings, with select loans from a private collection, “French Pastels: Treasures from the Vault” provides an exceptional opportunity to see firsthand nearly 40 seldom-shown masterworks by artists including Mary Cassatt, Edgar Degas, Edouard Manet, Jean-François Millet, Claude Monet, Camille Pissarro, Odilon Redon, and Pierre-Auguste Renoir.

The medium of pastel is deceptive; the colorful sticks seem so simple to use, but the powdery surface can be difficult to layer and fix. Pastel is immediate and, potentially, ephemeral. During the late 19th century, avant-garde artists in France and beyond took up pastels to capture the here and now, fleeting facial expressions, passing effects of light or weather, delicate blossoms that might soon wither. Pastels were perfectly suited to this aim: an evanescent medium for an evanescent subject. “That’s the triumph of this technique,” noted a French critic at the time, “it must capture what is most elusive.”

Notable works in the exhibition include Camille Pissarro’s Poultry Market at Gisors (1885) and Jean-François Millet’s Dandelions (1867–68), in which the artist exploits the chalky medium to describe the downy texture of dandelions gone to seed. Another of pastel’s foremost innovators was Edgar Degas, whose processes and fixatives still elude explanation. In Dancers Resting (1881–85), pictured above, Degas employs the powdery medium to dazzling effect, conveying the gossamer quality of the ballerina’s puffy tutu. The exhibition also features a pastel box that once belonged to Mary Cassatt.