Tempera Grassa
Egg and oil, emulsified. The paint dries tomorrow, stays flexible for centuries, and holds brushmarks that neither medium alone can carry.
Tempera grassa—"fat tempera"—is an emulsion medium combining egg yolk (the traditional tempera binder) with drying oil (linseed, walnut, or poppy) and water, sometimes with a small addition of dammar or copal resin. The resulting paint dries faster than oil, carries crisper brushmarks than oil, is more flexible than pure egg tempera, and can be built up in layers on the day of application rather than requiring weeks of drying between coats. The medium sits on a spectrum: pure egg tempera at one end, pure oil paint at the other, tempera grassa in the middle with variable proportions that let the painter tune toward either end depending on the painting's needs.
The medium has deep historical roots. The northern Renaissance used various egg-oil emulsions as the paint moved from pure egg tempera toward oil through the fifteenth century—van Eyck's medium has been analyzed as a form of tempera grassa, and many early Netherlandish panels show emulsion-medium layers under the translucent oil glazes they are famous for. Andrew Wyeth's late tempera practice used a grassa-adjacent medium for the more flexible passages. The modern revival—the Society of Tempera Painters, Koo Schadler, Fred Wessel—has codified recipes and documented the medium's specific behavior. The paint is not a compromise between tempera and oil; it is a distinct medium with its own handling and its own rightful uses.
The practice is less forgiving than oil. Tempera grassa dries quickly—passages set within hours, not days—which means the painter cannot work back into a passage the way oil allows. The handling is more like egg tempera: build the painting in thin, disciplined layers, with each layer planned to contribute a specific tonal or chromatic note to the stack. When the method is used well, the finished painting has a luminosity and a surface quality that neither pure tempera nor pure oil produces. When it is used poorly—thick passages, muddled layers, no planning—it produces a surface that fails in specific, diagnosable ways: cracking if too fat, chalky if too lean, sticky if the proportions are wrong.
Mix the medium fresh
Tempera grassa is mixed fresh daily or every few days. The egg yolk spoils; the emulsion separates if held too long. A painter working in this medium accepts a standing morning ritual—separate the egg, mix the medium, test the behavior—as part of the practice. The shortcut of using pre-mixed medium jars has no place here; the medium is part of what the painter makes.
Build in thin disciplined layers
The medium does not support thick impasto. Every layer is thin, considered, and contributes one note—a tonal shift, a chromatic glaze, a hatched passage of cool over warm. A painter treating tempera grassa like oil, loading the brush and laying in thick marks, has misused the medium; the paint will crack or fail over time. The discipline is layering discipline.
Tune the fat-lean ratio to the layer
The proportion of oil to egg can be varied between layers. Early layers lean toward egg (leaner, faster drying, matte). Later layers can move toward oil (fatter, slower drying, glossier) to honor the fat-over-lean rule that keeps the paint film stable. A painter who keeps the ratio fixed across every layer loses the medium's central advantage—the ability to tune behavior layer by layer.
Work on a rigid support
Tempera grassa is less flexible than oil. On canvas, it can crack over time as the canvas moves. The medium's natural support is a rigid panel—traditionally gesso on wood, in modern practice acrylic gesso on hardboard or aluminum. A painter committing to this medium commits to the support as well; working on stretched canvas is inviting long-term conservation problems.
Andrew Wyeth1917–2009
The twentieth-century most-visible revivalist—tempera-adjacent medium used across the Kuerner Farm and Chadds Ford tempera output.
Painter process →botticelli
The Italian Renaissance transitional case—Botticelli's panels are predominantly tempera with oil-adjacent upper layers, a proto-grassa practice.
Gustav Klimt1862–1918
The Vienna Secession mixed-media practice—gold leaf, egg tempera, and oil coexisting on single panels, with grassa-adjacent emulsion layers mediating.
Painter process →The Cracked Canvas
A painter applies tempera grassa on stretched canvas and years later finds the paint cracking along the stretcher bars and wherever the canvas flexes. The medium was mismatched to the support. The fix is to accept the support constraint: serious tempera grassa work goes on rigid panels, not canvas. The fix for an already-painted canvas is conservation work by a specialist—no at-studio remedy will hold.
The Wrong Ratio
A painter mixes the medium once and uses the same ratio for every layer. Either the early layers are too fat and later layers fail to bond, or the later layers are too lean and the surface cracks. The fix is layer-by-layer thinking: each layer gets a medium tuned to its job, leaner early, fatter late.
The Oil Handling
A painter adopts tempera grassa and works it like oil—thick passages, loading the brush, painting back into wet passages for hours. The paint dries faster than the handling assumes; passages set up muddy and the layer stack fails. The fix is to learn the medium as itself, not as a variant of oil. Spend the first ten paintings mastering the layering logic before attempting anything ambitious.
Prepare three rigid panels—nine-by-twelve hardboard or aluminum, primed with acrylic gesso or traditional gesso. Mix tempera grassa fresh daily from a documented recipe. Paint nothing ambitious; practice the medium's handling through thin monochrome studies.
A small still life in tempera grassa at nine-by-twelve. Build in deliberate layers: grisaille stage first, then color glazes, then small opaque highlights. The finished painting is a demonstration of the layering logic.
A larger piece at sixteen-by-twenty on panel. Figure study or interior. Push the layer count—eight to fifteen layers—with tuned fat-lean ratios across the stack.
Paint the same subject twice—once in tempera grassa on panel, once in oil on canvas, same scale, same session length. Compare the surfaces. The tempera grassa version will have a different luminosity and a different brushmark quality than the oil; the point is to feel where each medium is strongest and to know when each is the right choice.
Tempera grassa is not a shortcut to oil-like behavior or to tempera-like behavior—it is its own medium, mixed fresh, built in thin disciplined layers on a rigid panel, with the fat-lean ratio tuned layer by layer. Master it as itself, or do not use it.
- Cennino Cennini. Il libro dell'arte, 1400 (Italian). The earliest surviving description of tempera-oil emulsion practice in the Italian workshop tradition.
- Daniel V. Thompson. The Practice of Tempera Painting, 1936. The twentieth-century technical consolidation of tempera and tempera-grassa practice—the modern reference for recipes and handling.
- Koo Schadler. Egg Tempera Painting: A Comprehensive Guide, 2005. The contemporary revival documentation—tempera and tempera-grassa practice in modern studios, with tested recipes and failure analysis.
Last researched: 2026-04-19