Binders

Part of Pigments and Paint

Paint binder types and preparation — the substances that hold pigment particles together and attach them to surfaces.

Why This Matters

Pigment without binder is just colored dust. It sits on a surface until the first rain washes it away or the first touch smears it. The binder is the critical ingredient that transforms loose pigment into durable paint, and choosing the right binder determines whether a coating lasts weeks or decades. Every paint system in history — from Paleolithic cave paintings to Renaissance oils to industrial enamels — is defined more by its binder than by its pigments.

In a rebuilding scenario, binder selection depends on what materials are locally available and what the paint must accomplish. A waterproof coating for a boat hull needs a different binder than a decorative wall paint, which needs a different binder than a permanent ink for records. Fortunately, effective binders can be made from animal products, plant materials, and mineral sources found in virtually any environment.

Understanding binders also unlocks the ability to match paint to purpose. A community that can produce three or four different binder types can create paints for every application — from rough exterior weatherproofing to fine interior decoration to permanent document illustration. This versatility is a significant quality-of-life improvement and a practical necessity for maintaining infrastructure.

Binder Categories

Overview

Binder Type	Source	Dries By	Durability	Best For
Lime (calcium hydroxide)	Limestone + heat	Chemical reaction (carbonation)	Excellent — centuries	Walls, masonry, exteriors
Egg tempera	Chicken eggs	Evaporation + oxidation	Very good — centuries	Fine art, detailed work, signage
Hide glue	Animal skins/bones	Evaporation (reversible)	Good indoors; poor in damp	Interior walls, gesso, gilding
Casein	Milk curds + alkali	Chemical reaction	Very good — hard, waterproof	Furniture, wood, general purpose
Drying oils	Linseed, walnut, poppy	Oxidation polymerization	Excellent — flexible, waterproof	Exterior wood, metal, fine art
Plant gums	Acacia, cherry, etc.	Evaporation (reversible)	Fair — water-soluble	Watercolor, illumination, ink
Beeswax	Beehives	Cooling/solidification	Good — water-resistant	Encaustic painting, polish
Pine pitch/tar	Pine trees	Evaporation + oxidation	Very good — waterproof	Waterproofing, exterior wood

Lime Binder (Fresco)

The oldest durable binder, used since antiquity. Lime-bound paint literally becomes part of the wall.

Preparation

1. Burn limestone — heat limestone (calcium carbonate) in a kiln at 900+ C to produce quicklime (calcium oxide)
2. Slake the quicklime — carefully add water to quicklime. This reaction is violent and exothermic — add water slowly, wearing eye protection, standing upwind.

Quicklime Safety

Quicklime reacts violently with water, generating intense heat and spattering caustic material. Always add water to quicklime (never the reverse), wear eye protection, and keep skin covered. Burns from quicklime are severe.

3. Age the putty — the resulting lime putty (calcium hydroxide) improves with aging. Store submerged under water in a sealed container for at least 3 months; a year or more is better. Aged lime putty is smoother, more workable, and produces better paint.
4. Mix with pigment — combine lime putty with pigment and water to the desired consistency

Application (Fresco Technique)

True fresco painting is done on fresh, wet lime plaster:

1. Apply a coat of lime plaster to the wall
2. While the plaster is still damp, paint directly onto it with pigment mixed in lime water
3. As the plaster dries, it undergoes carbonation — the calcium hydroxide absorbs carbon dioxide from the air and converts back to calcium carbonate, permanently locking the pigment into the wall surface
4. The result is essentially colored stone — extraordinarily durable

Limitations

• Only works on fresh, wet lime plaster (secco application on dry plaster is much less durable)
• Not all pigments are compatible — lime is strongly alkaline, which destroys some organic pigments
• Must work quickly before the plaster dries (typically 4-8 hours per section)

Egg Tempera

The standard binder for fine painting from antiquity through the 15th century. Produces vivid, permanent colors.

Preparation

1. Separate the yolk — crack an egg and pass the yolk between the shell halves, letting the white drip away
2. Remove the membrane — pinch the yolk sac and roll it on your palm until clean, then puncture it over a container, letting the pure yolk flow out. Discard the membrane.
3. Mix with water — add roughly equal volume of water to the pure yolk; stir well
4. Combine with pigment — grind pigment into the yolk-water mixture on a flat stone or glass slab using a muller. Work until completely smooth.

Properties

• Drying time: 15-30 minutes per layer (very fast)
• Appearance: matte to semi-matte; colors remain vivid for centuries
• Layering: build up color in thin, translucent layers
• Durability: excellent on rigid surfaces (wood panels, plaster); poor on flexible surfaces (it cracks)
• Shelf life: must be mixed fresh daily — egg yolk spoils within hours in warm weather

Preservation Trick

Adding a drop of vinegar or a tiny pinch of salt to the egg yolk mixture slows spoilage, giving you several extra hours of working time.

Hide Glue Binder

Made from animal skins, hooves, bones, and connective tissue. The most accessible animal-derived binder.

Preparation

1. Source material — collect scraps of rawhide, skin, sinew, or bones
2. Clean — wash thoroughly, removing any flesh or fat
3. Simmer — cover with water in a pot and simmer (do not boil) for 4-8 hours until the liquid becomes thick and syrupy
4. Strain — filter through cloth to remove solid debris
5. Test concentration — let a drop cool on a flat surface. It should gel within minutes. If it remains liquid, simmer longer to concentrate.
6. Mix with pigment — combine warm glue solution with pigment to the desired consistency

Properties

• Reversible — hide glue dissolves in warm water, making it easy to repair or repaint
• Interior use only — humidity and rain soften hide glue paint
• Good adhesion — bonds well to wood, plaster, cloth, and paper
• Excellent for gesso — hide glue mixed with chalk or gypsum creates gesso, the standard ground for painting on wood panels

Drying Oils

The most durable and versatile binders, used for everything from fine art to ship paint.

Oil Sources

Oil	Drying Speed	Quality	Source
Linseed (flax)	Fast (2-5 days)	Excellent — standard artist’s oil	Flax seeds, cold-pressed
Walnut	Medium (3-7 days)	Very good — less yellowing than linseed	Walnut meats, pressed
Poppy seed	Slow (5-10 days)	Good — least yellowing	Poppy seeds, pressed
Hemp seed	Fast (2-5 days)	Good	Hemp seeds, pressed
Tung	Very fast (1-2 days)	Excellent — hardest film	Tung tree nuts

Preparing Drying Oil

Raw pressed oil dries very slowly. Processing improves it dramatically:

Sun-thickened oil:

1. Pour raw oil into a wide, shallow dish
2. Cover with a glass pane or stretched cloth to keep out debris while allowing air circulation
3. Set in direct sunlight for 2-4 weeks, stirring occasionally
4. The oil thickens, lightens in color, and dries much faster when used as a binder

Heat-bodied (stand) oil:

1. Heat raw oil in a metal vessel to 250-300 C
2. Maintain temperature for 4-8 hours, stirring occasionally
3. The oil polymerizes, becoming thick and syrupy
4. This oil produces an extremely tough, flexible paint film

Oil Heating Safety

Heating oil above its flash point causes it to burst into flame. Never heat oil over an open flame — use a double-boiler arrangement or heat in sand. Keep a metal lid nearby to smother any fire. Never use water on an oil fire.

Mixing Oil Paint

1. Grind pigment — place dry pigment on a flat stone slab
2. Add oil gradually — pour a small amount of prepared oil onto the pigment
3. Mull — use a stone muller (a flat-bottomed grinding stone) to work the oil into the pigment using circular motions with firm pressure
4. Continue grinding — add more oil as needed until the paint reaches the consistency of thick cream. Different pigments absorb different amounts of oil.
5. Test — paint a thin stripe on a test surface. It should flow smoothly without dripping and dry to a uniform film within 2-5 days.

Plant Gum Binders

Water-soluble binders from tree saps, used for watercolor painting and manuscript illumination.

Gum Arabic (Acacia Gum)

The gold standard of plant gum binders:

1. Collect — harvest hardened sap nodules from acacia, cherry, plum, or similar trees
2. Dissolve — break gum into small pieces and cover with twice the volume of warm water. Let stand 24-48 hours, stirring occasionally, until fully dissolved.
3. Strain — filter through fine cloth to remove bark and debris
4. Preserve — add a drop of clove oil or a tiny amount of vinegar to prevent mold
5. Mix with pigment — combine gum solution with pigment for watercolor or ink

Properties

• Produces brilliant, transparent colors
• Completely water-soluble (reversible)
• Excellent for fine detail work and calligraphy
• Not suitable for exterior use — rain dissolves it immediately
• Stores well as a dry gum; reconstitute with water when needed

Beeswax Binder (Encaustic)

An ancient technique using heated beeswax as the binder. Produces rich, luminous, waterproof paint.

Preparation

1. Melt beeswax — gently heat beeswax in a double boiler until liquid
2. Add pigment — stir dry pigment into the melted wax
3. Optional: add resin — mixing in 10-20% tree resin (pine, damar) by weight hardens the wax and improves adhesion
4. Apply hot — use a heated metal palette knife or stiff brush to apply the wax-pigment mixture while it is still liquid
5. Fuse — after application, pass a heat source (hot iron, heated stone) close to the surface to fuse the layers together

Properties

• Waterproof and extremely durable (Egyptian encaustic portraits survived 2,000+ years)
• Rich, saturated colors with a slight translucency
• Requires heat to apply — limits working conditions
• Excellent for outdoor signage and decoration in wet climates

Choosing the Right Binder

Application	Recommended Binder	Why
Exterior walls	Lime	Carbonation makes it permanent; breathable
Interior walls	Hide glue or lime	Easy to apply; hide glue is easy to repair
Wood furniture	Casein or drying oil	Hard, durable, water-resistant
Boat hulls	Drying oil or tar/pitch	Maximum waterproofing
Metal protection	Drying oil	Flexible film resists expansion/contraction
Fine artwork	Egg tempera or oil	Permanent, vivid colors
Signs and records	Egg tempera or casein	Durable, legible, easy to apply
Manuscripts/books	Plant gum (watercolor)	Thin application, fine detail, no warping
Outdoor signage	Encaustic (beeswax) or oil	Waterproof, weather-resistant

For detailed casein binder preparation, see Casein Binder.