Exploring Egg Tempera and Tempera Grassa: Mastering Historical Painting Techniques

Egg Tempera and Tempera Grassa Techniques for Modern Artists

For centuries, the art world has been captivated by the luminous and enduring beauty of works by the Old Masters. At the heart of many historic masterpieces lies a choice of materials that has shaped the aesthetic and durability of these works: egg tempera and tempera grassa techniques. Understanding these mediums provides invaluable insights for contemporary artists striving to achieve similar effects in their work.

A new study offers important insights into egg tempera and tempera grassa techniques by recreating paint samples and highlighting how these are identified in a few 15th-century paintings. The authors published their findings in “Tempera and Tempera Grassa─From Wet Paints to Solid Films,” published in Applied Polymer Materials.

The drying process of egg tempera is rapid, occurring within mere seconds to minutes due to water evaporation. This swift drying time necessitates a unique approach to achieving color transitions. Instead of blending paints of different hues directly in the painting, artists layer them in numerous thin, translucent strokes. This technique, known as hatching, allows for the modulation of a paint’s hiding power through the density of the applied layers, facilitating the gradual transition of colors. For instance, the nuanced flesh tones in historical paintings are accomplished by layering brownish, pink, and white hues over a greenish underlayer, which subtly emerges in select areas, contributing to the depth and realism of the depiction.

Conversely, the drying process of oil paints unfolds over several days through chemical cross-linking, enabling artists to blend colors. This wet-in-wet technique permits the seamless merging of hues, facilitating smooth transitions and gradients that are characteristic of oil paintings.

Historical artworks sometimes reveal an intermediary stage between tempera and oil painting, where the paints exhibit hybrid properties. An illustrative example can be found in Jacopo del Sellaio’s Martyrdom of Saint Sebastian, where certain paints unexpectedly demonstrate a uniformity in thickness and color regardless of the number of brushstrokes applied. This suggests that the paints remained fluid enough to merge and level post-application, diverging from the quick-drying nature of egg tempera. Additionally, the texture of the white paint on the crossbow is reminiscent of oil paint rather than tempera, indicating a blend of mediums.

The practice of adding oil to tempera, presumed to slow the drying time, gives rise to the concept of “tempera grassa” or “fatty tempera”—a fusion of egg yolk with drying oils. Although “tempera grassa” is not extensively documented in historical technical treatises, its identification in artworks often relies on the detection of both egg and oil in a paint layer through chemical analysis. However, such detailed analysis is not always feasible. Consequently, paints exhibiting characteristics akin to oil but identified as tempera are sometimes classified as tempera grassa based on visual inspection and the comparative experience of their properties rather than through empirical analysis.