Tempera is a fast-drying, water-based paint that produces a distinctive matte finish with luminous color. In its traditional form, known as egg tempera, it consists of powdered pigment mixed with egg yolk and water. The egg yolk acts as a natural emulsifier, binding pigment particles together into a thin, workable paste. These simple ingredients give tempera a set of physical and visual qualities unlike any other painting medium.
What Tempera Is Made Of
True egg tempera has only three ingredients: ground pigment, egg yolk, and water. The yolk is the key. It contains both oily and water-soluble components, making it a natural emulsion that suspends pigment evenly and bonds it to a surface as the paint dries. Water thins the mixture into a paste that can be applied with a brush, but the yolk is what holds everything together once the water evaporates. Manufactured versions of egg tempera sometimes add plant-based gums as dispersants to keep the pigment from clumping in the tube.
It’s worth noting that the “tempera paint” sold in craft stores and used in school art classes is a completely different product. Modern poster tempera replaces the egg yolk with starch, cellulose, or other glue-based binders. It’s non-toxic and easy to use, but it lacks the permanence, color depth, and handling qualities of egg tempera. When art historians and professional painters talk about tempera, they mean the egg-based version, which dates back to at least the 3rd century and dominated European panel painting until oil paints overtook it in the 1500s.
Rapid Drying, Slow Curing
Speed is one of tempera’s most defining traits. A thin brushstroke applied to a prepared panel dries in seconds. This happens because tempera is an oil-in-water emulsion: water makes up the continuous phase, and once that water evaporates, the surface feels dry almost immediately. That rapid set time is why tempera painters traditionally work in small, precise strokes rather than blending large areas of wet paint together.
But “dry to the touch” isn’t the same as fully cured. After the water evaporates, the oily components of the egg yolk undergo a much slower chemical process. Over days and weeks, fatty acids in the yolk oxidize and polymerize, gradually forming a harder, more durable film. This two-stage process, fast physical drying followed by slow chemical hardening, gives tempera paintings their long-term stability. Centuries-old tempera panels in museum collections remain in remarkable condition partly because that cured egg film is extremely tough.
Matte Finish and Luminous Color
Tempera dries to a soft, matte surface that looks nothing like the glossy sheen of oil paint or acrylic. The egg yolk binder has a low refractive index (around 1.35), meaning it doesn’t bend light the way an oil binder does. Instead of creating a glassy layer over the pigment, the dried egg film lets pigment particles scatter light more diffusely. The result is a chalky, velvety surface with colors that appear bright and almost opaque, but without shine.
This matte quality also means tempera colors don’t shift much between wet and dry states. Oil paint often looks darker once it dries because the binder changes how light passes through the pigment layer. Tempera stays closer to what you see on the brush. For painters, this predictability is a major advantage when building up precise color work, which is one reason tempera was the preferred medium for the detailed icon paintings and altarpieces of the Middle Ages and early Renaissance.
Thin Layers and Building Technique
Tempera cannot be applied in thick, buttery strokes the way oil paint can. The medium works best in thin, semi-transparent layers built up gradually. Each stroke dries so quickly that blending on the surface is nearly impossible, so painters create tonal transitions by crosshatching or layering many fine strokes of slightly different values on top of one another. This technique produces a distinctive visual texture: up close, you can often see individual brushstrokes, but from a normal viewing distance, the colors merge smoothly.
The thinness of each layer also contributes to tempera’s luminosity. When applied over a bright white ground, light passes through the semi-transparent paint, bounces off the white surface beneath, and travels back through the color layer to your eye. This gives tempera paintings an inner glow that thicker, more opaque media don’t achieve as easily.
Rigid Supports and Gesso Ground
Tempera demands a rigid, properly prepared surface. Wood panels have been the standard support for centuries because they don’t flex the way stretched canvas does. This matters because dried tempera film, while hard, is also brittle. Even small movements in the support can cause the paint layer to crack.
Before any paint goes on, the panel is coated with gesso, a preparatory ground traditionally made from gypsum (a calcium sulfate mineral) mixed with animal-hide glue. This gesso layer serves two purposes: it provides a smooth, absorbent white surface for the paint to grip, and it acts as an intermediary between the wood and the paint. Traditional gesso formulations are themselves quite stiff and brittle, with very low flexibility. That brittleness, combined with the rigid nature of the paint layers above, makes the entire structure sensitive to environmental changes. Fluctuations in humidity and temperature cause wood to expand and contract, and the mechanical mismatch between a moving wooden support and the stiff gesso and paint layers above it is the primary reason conservators find cracks in historical tempera paintings.
This vulnerability is the trade-off for tempera’s other strengths. The medium is chemically stable and resistant to yellowing, but it needs a controlled environment to survive long term. Museum climate systems exist in part because of how tempera (and similarly rigid paint systems) respond to environmental stress.
How Tempera Compares to Oil Paint
Understanding tempera’s qualities becomes easier when you contrast them with oil paint, the medium that largely replaced it. Oil paint uses a drying oil (typically linseed) as its binder instead of egg yolk. That oil binder dries far more slowly, giving painters minutes or even hours to blend colors directly on the surface. Oil also allows thick application, creating visible texture and impasto effects that tempera simply can’t achieve.
On the other hand, oil paint yellows over time, dries with a glossy finish that may require varnishing to control, and shifts noticeably in value between wet and dry. Tempera avoids all three of those issues. Its colors remain stable for centuries, its matte surface needs no varnish (though some painters choose to apply one), and its wet-to-dry color shift is minimal.
The choice between the two has always been about trade-offs. Oil offers flexibility, blendability, and textural range. Tempera offers speed, color accuracy, permanence, and a distinctive luminous surface. Many Renaissance painters, including Botticelli, used egg tempera for its precision and then applied thin oil glazes on top to get the best of both worlds.