Egg tempera was the primary painting medium for European panel paintings before oil paint became dominant in the 15th century. Many Botticelli works use egg tempera.
For roughly five centuries, from the early medieval period through the late 1400s, egg tempera was the primary medium for panel painting in Europe. Every significant work of European painting from that period, from the gold-ground icons of the Byzantine tradition to the early Renaissance panels of Florentine masters including Sandro Botticelli, was made with paint bound by egg yolk. The switch to oil paint in the 15th and 16th centuries was one of the most significant technical transitions in art history, and it did not happen because egg tempera was inadequate. It happened because oil offered specific capabilities that egg could not match.
## How Egg Tempera Works
Egg tempera is made by combining dry pigment with egg yolk, sometimes diluted with water and occasionally with a small amount of vinegar or wine to retard spoilage. The yolk contains both water and lipids, which allows it to bind pigment in a way that adheres firmly to prepared surfaces, typically gesso-covered wood panels. As the paint dries, the water evaporates and the lipid components begin a slow oxidative polymerization that eventually produces an extremely hard, stable film.
The technical properties of egg tempera determine the visual character of the works made with it. The paint dries rapidly, typically within minutes, which prevents the kind of wet-into-wet blending that is possible with oil. Instead, tempera painters built up form through hatching: layers of fine parallel strokes that optically mix on the viewer's eye. This technique is visible in detail photographs of Botticelli's Birth of Venus and Primavera, both painted in egg tempera in the 1480s. The flesh tones in these works are built from dozens of translucent hatched layers, not from blended gradients.
## The Transition to Oil
The shift from tempera to oil paint began in the Netherlands in the early 15th century and is traditionally associated with Jan van Eyck, though the specific technical innovations involved remain debated by art historians. Oil paint dries more slowly, allowing extensive blending and correction. It can be applied in thick impasto passages or in thin glazes. It accommodates a wider range of surface textures and can simulate atmospheric effects, particularly the soft transitions of light through air, that are difficult or impossible to achieve in tempera.
Italian painters adopted oil techniques gradually through the second half of the 15th century. Leonardo da Vinci used oil extensively. By the early 16th century, tempera had been largely displaced for large-scale panel and canvas painting in Italy, though it continued in use for underdrawing and in some regional traditions.
Egg tempera was revived deliberately by 19th-century artists interested in pre-Renaissance techniques and again in the 20th century, most notably by American painter Andrew Wyeth, who made it the primary medium of his career. The medium's durability has been confirmed by the survival of tempera panels from the 13th century in better condition than many oil paintings from the 17th century. The egg yolk that bound Botticelli's paint has outlasted most of the buildings that have stood since his lifetime.