Tempera Paint

Part of Pigments and Paint

Making tempera paint using various emulsion binders beyond egg yolk.

Why This Matters

Tempera is not a single paint but a family of paints based on emulsion binders — any mixture of water and oil or fat held in stable suspension by an emulsifying agent. While egg yolk tempera is the most famous, tempera paints can be made from dozens of different emulsions: casein (milk protein), hide glue with oil, gum arabic, starch paste, and even plant sap. This versatility is critical for a rebuilding community because it means you can make high-quality paint regardless of which specific materials your environment provides.

Tempera paints share important advantages over oil paints: they dry quickly (minutes rather than days), they do not yellow with age, they produce a bright matte finish, and they can be made and applied in the same day. For signage, diagrams, instructional murals, and interior decoration, tempera is often the better choice. Oil paint’s advantages — weather resistance and flexibility — only matter for exterior applications.

Understanding tempera formulation also teaches emulsion chemistry, a concept that applies to many other technologies: soap-making, leather processing, food preparation, and pharmaceutical compounding all rely on creating stable mixtures of oil and water phases.

Emulsion Fundamentals

An emulsion is a stable mixture of two immiscible liquids — typically oil and water. In tempera paint, the emulsion serves as the binder that holds pigment particles together and adheres them to the painting surface.

Components of a tempera emulsion:

• Water phase: Carries the paint, allows flow, evaporates during drying
• Oil/fat phase: Remains after drying, provides film toughness and water resistance
• Emulsifier: Keeps oil and water mixed — without it, they separate

Natural emulsifiers:

Emulsifier	Source	How It Works
Lecithin	Egg yolk, soybeans	Phospholipid with water-loving and oil-loving ends
Casein	Milk protein	Forms micelles around oil droplets
Saponin	Various plants (soapwort, yucca)	Natural surfactant
Gum arabic	Acacia tree sap	Polysaccharide that stabilizes oil-water interfaces
Starch	Grains, roots	Thickens water phase to prevent separation

Casein Tempera (Milk Paint)

Casein — the protein in milk — makes an excellent paint binder that dries to a hard, durable finish. Casein paint was used on furniture and interior surfaces for centuries before commercial paints became available.

Extracting Casein

1. Start with skim milk (or whole milk — the cream adds useful oil)
2. Warm to about 40C (body temperature)
3. Add vinegar or lemon juice — approximately 2 tablespoons per liter of milk
4. Stir gently. The milk curdles — white curds (casein) separate from the clear whey
5. Strain through cloth to collect the curds
6. Rinse the curds with clean water to remove residual whey
7. Press out excess water — you now have fresh casein

Making Casein Paint

Method 1 — Quick mix:

1. Crumble fresh casein into a bowl
2. Add a small amount of lime water (clear liquid above settled slaked lime) or borax solution — this dissolves the casein into a smooth, paint-like consistency
3. Stir until smooth and uniform
4. Add finely ground pigment
5. Mix thoroughly and thin with water to painting consistency

Method 2 — Casein-oil emulsion (more durable):

1. Dissolve casein in lime water as above
2. Add a small amount of linseed oil (10-15% of total volume)
3. Stir vigorously to emulsify — the casein acts as the emulsifier
4. Add pigment and mix
5. This produces a tougher, more water-resistant film than pure casein paint

Properties of Casein Paint

• Dries in 1-2 hours to a hard, matte finish
• Very strong adhesion to wood, plaster, and paper
• Moderate water resistance (good enough for interior use, not for exterior)
• Does not yellow with age
• Can be polished to a soft sheen when dry
• Shelf life of mixed paint: 2-3 days (casein spoils quickly)

Casein Powder

For longer storage, dry the fresh casein curds completely and grind to powder. Store in a sealed container. Reconstitute by dissolving in lime water when needed. Dried casein keeps for months.

Glue Tempera (Distemper)

Hide glue or gelatin makes a simple, effective binder for interior paints — traditionally called “distemper.”

Making Glue Tempera

1. Prepare hide glue solution: soak dried hide glue pieces in cold water for 2 hours, then warm gently (do not boil) until dissolved. Standard concentration: 1 part glue to 10 parts water
2. Add pigment to the warm glue solution, stirring until uniform
3. Adjust consistency with water
4. Apply while warm — glue paint gels as it cools

Properties

• Very economical — hide glue is easily produced from animal skins, bones, and hooves
• Soft, velvety matte finish
• No water resistance — re-soluble when wet
• Easy to recoat — new paint dissolves and bonds with old layers
• Historically the standard interior wall paint across Europe and Asia
• Cannot be used on exterior surfaces

Glue-Oil Tempera (Enhanced Distemper)

For improved durability:

1. Prepare standard glue solution as above
2. While warm, add linseed oil at 10-20% of total volume
3. Stir vigorously to emulsify — the gelatin acts as the emulsifier
4. Add pigment
5. Apply while warm
6. The oil component adds water resistance and flexibility

Gum Tempera

Gum arabic and similar tree gums produce watercolor-type paints.

Preparation

1. Dissolve gum arabic in warm water — 1 part gum to 2 parts water. Stir until fully dissolved (may take several hours)
2. Strain through fine cloth to remove bark fragments
3. Add pigment to the gum solution
4. Mix until smooth

Properties

• Very transparent — best for layered, luminous effects
• Dries in minutes
• Re-soluble in water (can be re-wet and reworked)
• Excellent for manuscript work, maps, and fine detail
• Not durable enough for wall painting or signage

Gum-Honey Addition

Adding honey to gum tempera modifies its properties:

• Mix 1 part honey to 10 parts gum solution
• The honey prevents the paint from becoming brittle
• Paint remains slightly tacky — cover finished work to prevent dust adhesion
• Produces smoother brushwork

Starch Tempera

For communities without access to eggs, milk, or tree gums, starch paste from grains or roots provides a serviceable binder.

Making Starch Binder

1. Mix wheat flour, rice flour, or arrowroot powder with cold water at 1:4 ratio
2. Heat slowly while stirring constantly
3. The mixture thickens into a smooth paste at about 70C
4. Continue heating gently for 5 minutes to fully cook the starch
5. Cool to room temperature
6. Thin with additional water to desired consistency

Using Starch Tempera

1. Mix pigment into the cooled starch paste
2. Apply with brush to paper, wood, or plaster
3. Dries in 30-60 minutes
4. Produces a flat, matte finish
5. Moderate adhesion — better on absorbent surfaces
6. No water resistance — interior use only

Biological Instability

Starch binders are susceptible to mold and insect attack. Add a few drops of vinegar or essential oil (clove, thyme) as a preservative. Mix only what you need for one day.

Comparing Tempera Binders

Binder	Durability	Water Resistance	Drying Time	Availability	Best For
Egg yolk	Excellent	Moderate	5-15 min	Requires poultry	Fine painting, durable signs
Casein (milk)	Very good	Moderate	1-2 hours	Requires dairy animals	Furniture, interior wood
Hide glue	Moderate	None	30-60 min	Animal processing	Interior walls
Gum arabic	Good	None	5-10 min	Acacia trees	Manuscripts, maps
Starch	Low-moderate	None	30-60 min	Any grain/root crop	Temporary work, paper
Egg-oil emulsion	Excellent	Good	15-30 min	Poultry + oil crop	Durable panels, semi-exterior
Casein-oil emulsion	Very good	Good	1-2 hours	Dairy + oil crop	Furniture, interior walls

Working with Tempera

General Techniques

All tempera paints share certain working characteristics:

1. Thin layers: Apply in multiple thin coats rather than one thick coat. Thick tempera cracks
2. Quick drying: Work quickly — tempera dries fast and cannot be blended on the surface
3. Build opacity gradually: Each coat adds coverage. Allow full drying between coats
4. Cross-hatching: Alternate brush stroke direction between layers for uniform coverage
5. Do not overwork: Once paint begins to set (within seconds for egg and gum, minutes for casein and glue), do not go back over it — the brush will lift the paint

Surface Preparation

Tempera adheres best to absorbent surfaces:

• Wood: Sand smooth, apply gesso (chalk + glue size) for best results
• Plaster: Light sanding, no treatment needed if plaster is in good condition
• Paper: No preparation for most paper; sizing with dilute glue helps on very absorbent paper
• Canvas: Size with dilute glue solution, apply gesso

Varnishing Tempera

Tempera paintings can be varnished for protection after thorough drying (minimum 1 month for egg, 1 week for others):

1. Dissolve dammar or mastic resin in turpentine
2. Apply a thin, even coat with a soft brush
3. Allow to dry for 24 hours
4. Apply a second coat if desired
5. Varnish adds gloss, depth, and water resistance

Varnish Changes Appearance

Unvarnished tempera has a distinctive chalky, luminous matte quality. Varnishing darkens colors and adds gloss, changing the character significantly. Test on a sample before varnishing an important piece.

Storage

• Mixed paint: Use within 24 hours for egg tempera; 2-3 days for casein; glue paint can be reheated for weeks; gum paint stores for months in sealed containers
• Dry pigment-binder mixtures: Some tempera paints can be dried into cakes and reconstituted — gum tempera especially. This is how watercolor paint cakes work
• Binder solutions: Gum solution stores for months sealed. Glue solution stores for weeks (remelt before use). Casein solution must be used within days