In his paintings, Leonardo da Vinci used the oil paints of his time to explore qualities of light. In his notebooks, which included inventions such as the ornithopter, which enabled a person to operate two wings, da Vinci meticulously detailed his fascination with the quality of light, and he employed black and white pigments to study how light and shade blend and coexist. He developed foundational techniques such as sfumato, or a blurring of colors that generates soft outlines and which influenced generations of artists, including Rembrandt.
Sfumato was put to use in his touchstone masterpiece, the Mona Lisa, which was created not spontaneously but over a period of five years and in two stages. Da Vinci applied in excess of 40 layers of thin, translucent lacquer, with each layer only 10 to 50 micrometers thick. These layers cumulatively provided a realistic illusion of depth while mimicking the translucency of natural skin and were also applied to paintings such as the “Virgin of the Rocks.”
Da Vinci’s own description of sfumato is edifying, as he called it an approach “without lines or borders, in the manner of smoke or beyond the picture plane.” It complemented other efforts to create dimension and depth of space through the then-novel use of linear perspective. According to art scholars, da Vinci was seeking to transcend the limitations of the two-dimensional canvas, and he referred to astronomic studies of the sky and light, as well as an understanding of the elements in this.
Leonardo moved deftly from areas of soft and indeterminate clouds and mountains to intricate, fine details. In areas such as eyes, eyelids, and cheeks, one can also glimpse Leonardo’s fascination with the way light interacts with curved surfaces. He created this seamlessly, as a gauzy veil, in such a way that even the casual observer feels that real flesh and blood lies underneath. Notably, whether in the fingers or folds of cloth, the artist avoided outlines. He employed a chiaroscuro technique that involves the gradual application of contrasting colors and creates a sense of dimensionality and realism through the interplay of lightness and darkness.
Applying these theories to painting required a specific methodology grounded in the practices of da Vinci’s time. During his era, painters commonly painted on toned grounds known as imprimatura. His preference was for a white ground, such that light passed through the transparent layers of colors and reflected what appeared to the viewer an inner illumination.
Da Vinci created his brilliant white gesso through the use of lavender spike oil, a solvent that thinned his oil-based paints. This contravened the normal practice of the day, which was to dilute oil with more oil. For Leonardo, this had the unacceptable effect of limiting the number of layers that could be painted over each other, as well as causing unwanted yellowing (from the 17th century onward, painters often used turpentine as a solvent instead of lavender spike oil).
Another novel aspect of his oils was that da Vinci ground colors into walnut oil and then added a minute drop of amber resin that had been cooked in oil. The artist was a friend of a violin maker, and they were known to use such resin as a varnish for sealing their instruments. It was here that Leonardo likely found inspiration.
In a painting, the amber resin served to protect the colors from easy removal and damage, which ensured that the unparalleled depth and saturation of colors achieved would last many centuries. Precision characterized da Vinci’s technique, and he applied color with a small round brush, dipped in egg tempera before the paint, and worked meticulously, with a long-term perspective. Ultimately, having lived with the Mona Lisa for so many years during its creation, the artist decided to keep it for himself.
