How did Leonardo da Vinci use sfumato in the Mona Lisa?

In the Mona Lisa, Leonardo da Vinci utilized sfumato—a technique characterized by fine shading and soft, imperceptible transitions between colors and tones—to achieve a highly illusionistic effect.1

By applying oil paint in thin, translucent layers, Leonardo was able to build gradual shifts from light to dark, effectively blurring hard outlines. This approach allowed the subject’s facial features to appear gently modeled rather than sharply drawn, reflecting his deep understanding of the underlying musculature and skull structure.2

Furthermore, Leonardo used sfumato to ensure that the edges of the figure seem to blend seamlessly into the surrounding shadows and the atmospheric landscape, creating a sense of harmony where the subject appears to evaporate into the air around her. This delicate handling of tone is particularly evident in the sitter's faint smile and the soft, sculptural quality of her face, which helped establish the Mona Lisa as a standard for future portraiture.32