Egg Tempera

Part of Pigments and Paint

Making egg tempera paint using egg yolk as a binder for ground pigments.

Why This Matters

Egg tempera is one of the oldest and most durable paint formulations in human history, predating oil paint by centuries. In a rebuilding scenario, eggs are among the first animal products available once poultry flocks are established, making egg tempera one of the earliest high-quality paints you can produce. Unlike oil paints that require months of drying oil preparation, egg tempera can be mixed and applied the same day.

The durability of egg tempera is remarkable. Paintings from the 14th century remain vibrant today because the egg protein cross-links as it dries, forming a tough, flexible film that resists cracking and fading. For a rebuilding community, this means signs, maps, diagrams, and instructional illustrations can last for decades without maintenance.

Beyond art, egg tempera serves critical practical functions: marking tools and equipment, creating durable labels for storage containers, painting instructional diagrams on workshop walls, and producing weather-resistant signage. The technique requires minimal equipment and ingredients that any agricultural settlement will have access to.

Understanding Egg Yolk as a Binder

Egg yolk is a natural emulsion containing roughly 50% water, 32% fats and oils, and 16% protein, along with lecithin which acts as an emulsifying agent. This combination makes it uniquely suited as a paint binder because it can hold both water-soluble and oil-soluble pigments in suspension.

When egg tempera dries, the process occurs in two stages. First, the water evaporates, leaving a soft film. Then, over days to weeks, the proteins denature and the oils oxidize, creating a hard, insoluble coating. This two-stage process is why tempera paintings become increasingly durable over time.

Yolk Separation

The quality of your tempera depends on clean yolk separation:

1. Crack the egg and pass the yolk back and forth between the shell halves, letting the white drain away
2. Place the yolk on your palm and gently roll it to remove clinging white
3. Pinch the yolk sac between your fingers and hold it over your mixing surface
4. Puncture the sac with a knife tip and let the pure yolk flow out
5. Discard the sac membrane — it creates lumps in the paint

Critical Step

Any egg white mixed into the yolk will cause the paint to crack as it dries. Egg white dries to a brittle, inflexible film, while yolk remains flexible. Take extra time on separation.

One egg yolk provides enough binder for approximately a full day’s painting on a surface the size of a large book page.

Mixing Egg Tempera

Basic Ratio

The standard ratio is approximately equal volumes of egg yolk and ground pigment, adjusted by feel:

Pigment Type	Yolk-to-Pigment Ratio	Notes
Earth pigments (ochre, umber)	1:1	Most forgiving ratio
Charcoal/lamp black	1:0.5	Very absorbent, needs less pigment
White (chalk, lime)	1:1.5	Dense pigment, needs more
Mineral pigments	1:1	Test small batch first

Mixing Process

1. Place a small mound of finely ground pigment on a flat, non-porous surface (glass, polished stone, or glazed ceramic)
2. Create a well in the center of the pigment mound
3. Add egg yolk in small amounts — start with half the volume of pigment
4. Use a palette knife or flat stick to fold the pigment into the yolk
5. Work the mixture in circular motions, pressing and spreading to eliminate lumps
6. Add small amounts of water to adjust consistency — the paint should flow like cream
7. Test on a scrap surface: it should cover evenly without being transparent or gloppy

Shelf Life

Mixed egg tempera begins to spoil within 24 hours at room temperature. Mix only what you need for a single session. In cool weather (below 10C), mixed paint may last 2-3 days. Adding a drop of vinegar or a clove of crushed garlic can extend working life by a few hours.

Water Addition

Egg tempera is thinned with water, not with more yolk. Add water drop by drop while mixing. The paint should flow off a brush smoothly but not run down a vertical surface. Too much water makes the paint transparent and weakly bound. Too little makes it thick and prone to cracking.

Application Techniques

Egg tempera behaves differently from other paints. It dries very quickly — within minutes — and cannot be blended on the surface the way oil paint can. This demands a specific working method.

Building Up Layers

Tempera is applied in thin, semi-transparent layers called glazes. Each layer should be thin enough to partially see through:

1. First coat (underpainting): Apply a thin wash of the base color, diluted heavily with water. Let dry completely (15-30 minutes)
2. Second coat: Apply a slightly thicker layer. Brush strokes should be visible but even
3. Subsequent coats: Build up color intensity gradually. Each coat adds depth and richness
4. Final details: Use the paint at full concentration for fine lines and highlights

Brush Technique

• Use short, parallel strokes rather than long sweeping motions
• Work in one direction per layer, alternating direction between layers (cross-hatching)
• Do not go back over partially dried areas — this lifts the paint
• Clean brushes frequently in water; dried tempera is very difficult to remove

Surface Preparation

Egg tempera adheres best to absorbent surfaces:

• Wood panels: Sand smooth, apply a coat of diluted hide glue, then apply gesso (chalk mixed with hide glue)
• Plaster walls: Apply to fresh or lightly dampened lime plaster
• Paper/parchment: No preparation needed for thin applications
• Canvas: Size with hide glue, then apply gesso

Gesso Recipe

Traditional gesso is made by mixing fine chalk powder (calcium carbonate) with warm hide glue solution at roughly 1:1 ratio by volume. Apply 3-5 thin coats, sanding lightly between coats. The result is a smooth, brilliant white surface ideal for tempera.

Variations and Enhancements

Egg-Oil Emulsion

For slightly more flexible and water-resistant paint, add a small amount of drying oil to the yolk:

1. Separate one egg yolk as described above
2. Add approximately half a teaspoon of linseed oil (or walnut oil)
3. Mix thoroughly until the oil is fully incorporated
4. Use as normal egg tempera

This “tempera grassa” dries slightly slower, giving more working time, and produces a tougher final film.

Preserving Egg Yolk

In situations where eggs are seasonally available, you can extend their usefulness:

• Salted yolk: Mix yolk with an equal volume of salt. Stores for weeks in a cool place. Rinse salt off before use
• Vinegar preservation: Add a few drops of vinegar to separated yolks stored in a sealed container. Extends life to 3-5 days refrigerated or in a cool root cellar
• Dried yolk: Spread yolk thinly on a smooth surface and let dry completely. Reconstitute with water when needed. Quality is reduced but serviceable

Color Mixing

Because tempera dries quickly, premix all the colors you need before starting:

• Warm white: Chalk + tiny amount of yellow ochre + yolk
• Skin tones: White + yellow ochre + trace of red ochre + yolk
• Green: Mix blue (azurite or woad extract) with yellow ochre
• Brown: Raw umber + yolk
• Black: Charcoal or lamp black + yolk

Troubleshooting

Problem	Cause	Solution
Paint cracks after drying	Too thick application or egg white contamination	Apply thinner layers; improve yolk separation
Paint flakes off surface	Surface too smooth or oily	Sand surface, apply gesso, ensure no grease
Colors look chalky	Too much pigment relative to yolk	Add more yolk to the mixture
Paint won’t flow	Insufficient water	Add water drop by drop
Paint yellows over time	Normal for thick applications	Apply thinner layers; most yellowing fades
Mold growth on stored paint	Bacterial contamination	Add vinegar; mix fresh batches daily

Long-Term Durability

Properly applied egg tempera on a well-prepared surface will last for centuries. The key factors are:

• Surface preparation: Gesso or absorbent ground is essential
• Thin layers: Multiple thin coats outperform single thick ones
• Complete drying: Allow each layer to fully dry before adding the next
• Protection: A final coat of natural varnish (dammar or mastic resin dissolved in turpentine) adds water resistance and depth to colors

For practical applications like signage and workshop diagrams, egg tempera on wood panels provides years of service even without varnish. For surfaces exposed to weather, a varnish topcoat is essential.