Sfumato

Smoke and Shade Brought the Mona Lisa to Life

Public Domain image courtesy Wikimedia Commons
Leonardo da Vinci (Italian, 1452-1519). Mona Lisa (La Gioconda), ca. 1503-05. Oil on poplar wood. 77 x 53 cm (30 3/8 x 20 7/8 in.). Musée du Louvre, Paris

Sfumato (pronounced sfoo·mah·toe) is the word art historians use to describe a painting technique taken to dizzying heights by the Italian Renaissance polymath Leonardo da Vinci. The visual result of the technique is that there are no harsh outlines present (as in a coloring book). Instead, areas of dark and light blend into one another through miniscule brushstrokes, making for a rather hazy, albeit more realistic, depiction of light and color.

The word sfumato means shaded, and it is the past participle of the Italian verb "sfumare" or "shade." "Fumare" means "smoke" in Italian, and the combination of smoke and shade perfectly describes the barely perceptible gradation of tones and colors of the technique from light to dark, particularly used in flesh tones. An early, wonderful example of sfumato can be seen in Leonardo's Mona Lisa.

Inventing the Technique

According to the art historian Giorgio Vasari (1511–1574), the technique was first invented by the Primitive Flemish school, including perhaps Jan Van Eyck and Rogier Van Der Weyden. Da Vinci's first work incorporating sfumato is known as the Madonna of the Rocks, a triptych designed for the chapel in San Francesco Grande, painted between 1483 and 1485.

Madonna of the Rocks was commissioned by the Franciscan Confraternity of the Immaculate Conception, which at the time was still the object of some controversy.

The Franciscans believed that the Virgin Mary was conceived immaculately (without the benefit of sex); the Dominicans argued that would deny the need for Christ's universal redemption of mankind. The contracted painting needed to show Mary as "crowned in the living light" and "free from shadow," reflecting the plenitude of grace while humanity functioned "in the orbit of the shadow."

The final painting included a cave backdrop, which art historian Edward Olszewski says helped to define and signify Mary's immaculacy—expressed by the sfumato technique applied to her face as emerging from the shadow of sin.

Layers and Layers of Glazes

Art historians have suggested that the technique was created by the careful application of multiple translucent layers of paint layers. In 2008, physicists Mady Elias and Pascal Cotte used a spectral technique to (virtually) strip away the thick layer of varnish from the Mona Lisa. Using a multi-spectral camera, they found that the sfumato effect was created by layers of a single pigment combining 1 percent vermillion and 99 percent lead white.

Quantitative research was conducted by de Viguerie and colleagues (2010) using non-invasive advanced X-ray fluorescence spectrometry on nine faces painted by or attributed to da Vinci. Their results suggest that he constantly revised and improved the technique, culminating in the Mona Lisa. In his later paintings, da Vinci developed translucent glazes from an organic medium and laid them on the canvases in very thin films, some of which were only a micron (.00004 inches) in scale.

Direct optical microscopy has shown that da Vinci achieved flesh tones by superimposing four layers: a priming layer of lead white, a pink layer of mixed lead white, vermillion, and earth; a shadow layer made with a translucent glaze with some opaque paint with dark pigments, and a varnish.

 The thickness of each colored layer was found to range between 10-50 microns.

A Patient Art

The de Viguerie study identified those glazes on the faces of four of Leonardo's paintings: Mona Lisa, Saint John the Baptist, Bacchus, and Saint Anne, the Virgin, and the Child. Glaze thicknesses increase on the faces from a few micrometers in the light areas to 30–55 microns in the dark areas, which are made of up to 20–30 distinct layers. The thickness of the paint on da Vinci's canvases—not counting the varnish—is never more than 80 microns: that on St. John the Baptist is under 50.

But those layers must have been laid down in a slow and deliberate fashion. The drying time between layers may have lasted from several days to several months, depending on the amount of resin and oil that was used in the glaze.

That might well explain why da Vinci's Mona Lisa took four years, and it was still not completed at da Vinci's death in 1915.

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