Cooking Paste

Part of Adhesives

Making simple starch-based adhesive pastes.

Why This Matters

Starch paste is the most accessible adhesive a rebuilding community can produce. If you can grow grain, dig tubers, or collect acorns, you can make paste. The process requires nothing more than a starchy material, water, and heat. No specialized chemistry, no rare ingredients, no complex equipment. A child can make functional paste on their first attempt.

While starch paste lacks the strength of bone glue or the water resistance of birch tar, it excels in applications where those properties are unnecessary. Paper and fiber bonding, label attachment, bookbinding, wallpapering, papier-mache construction, light woodworking, and sealing envelopes and packages all work brilliantly with starch paste. These may sound like luxuries, but in a rebuilding community, the ability to bind paper into books preserves knowledge. The ability to seal packages enables trade. The ability to laminate fiber layers creates lightweight structural materials.

Starch paste is also the gateway adhesive, the first one a new community should master because it teaches the fundamental principles of adhesive preparation (heating, consistency control, application) with zero risk and minimal resource investment.

Starch Sources and Their Properties

Any plant material containing starch can produce paste. The concentration and quality vary significantly.

Source	Starch Content	Paste Quality	Availability	Notes
Wheat flour	70-75%	Excellent	Cultivated grain	The classic paste flour
Rice	75-80%	Excellent	Cultivated grain	Produces very smooth, clear paste
Corn/maize	65-72%	Very good	Cultivated grain	Produces slightly yellow paste
Potato	15-20% (fresh tuber)	Good	Cultivated/wild	Must extract starch or use raw
Tapioca/cassava	30-35% (fresh root)	Very good	Tropical cultivation	Strong, flexible paste
Acorns	40-50%	Fair	Wild foraged	Requires tannin removal first
Cattail roots	25-30%	Fair	Wild foraged	Seasonally available
Arrowroot	25-30% (fresh root)	Excellent	Wild/cultivated	Very fine, smooth paste

Best Choice

If available, rice starch or wheat flour produce the best general-purpose paste. Rice paste dries clear and smooth, making it ideal for paper and fabric work. Wheat paste has slightly better tack and is easier to prepare.

Basic Wheat Paste Recipe

This is the standard recipe used by bookbinders, papermakers, and craftspeople for centuries.

Ingredients

• 1 part white wheat flour (sifted to remove bran if using whole grain)
• 4-5 parts water
• Optional: pinch of salt (preservative), few drops of vinegar (mold inhibitor)

Process

1. Place flour in a mixing vessel
2. Add cold water gradually, about one-quarter of the total, stirring constantly to form a smooth slurry with no lumps
3. Continue stirring and bring the remaining water to a boil separately
4. Pour the hot water into the flour slurry in a thin stream, stirring vigorously and continuously
5. Transfer the mixture to a cooking vessel over gentle heat
6. Stir constantly as the mixture heats. At around 65-70 degrees Celsius, the paste will suddenly thicken dramatically as the starch granules swell and burst (gelatinization)
7. Continue cooking for 5-10 minutes after thickening, stirring throughout. This ensures complete gelatinization and develops maximum adhesive strength
8. Remove from heat and allow to cool, stirring occasionally to prevent a skin from forming

The finished paste should be smooth, translucent, and about the consistency of thick yogurt when cool. It should coat a brush evenly and spread without lumps.

The Lump Problem

Lumps are the enemy of good paste. They create uneven bonding and visible bumps under paper. If lumps form, press the paste through a straining cloth before use. Prevention is better: always add hot water to cold slurry, never the reverse, and never stop stirring during the heating phase.

Rice Paste

Rice paste is prized for fine paper work because it dries almost completely clear and produces a very smooth bond.

Process

1. Soak raw rice in water overnight until soft
2. Pound the soaked rice to a smooth pulp using a mortar and pestle
3. Add water to make a thin slurry (about 1 part rice pulp to 3 parts water)
4. Cook over gentle heat, stirring constantly, until the mixture thickens and becomes translucent
5. Strain through cloth to remove any remaining grain fragments
6. The resulting paste is exceptionally smooth and strong for its weight

Alternative quick method: Use rice flour if available. Follow the wheat paste recipe above, substituting rice flour. Rice flour gelatinizes at a slightly lower temperature than wheat, so watch carefully during heating.

Root Starch Paste

Potatoes, cassava, arrowroot, and other starchy roots produce excellent paste but require an extraction step to separate starch from fiber.

Starch Extraction

1. Wash and peel the root vegetable
2. Grate or pound into a fine pulp
3. Place the pulp in a cloth and knead it in a bowl of cold water. Starch particles wash out through the cloth into the water
4. Let the starchy water settle for 2-3 hours. Pure white starch settles to the bottom
5. Carefully pour off the water, retaining the starch sediment
6. Repeat the washing once more for purer starch
7. Dry the starch in a thin layer if storing for later use, or use wet starch immediately

Making Paste from Extracted Starch

1. Mix 1 part starch with 5-6 parts cold water, stirring until dissolved
2. Heat gently while stirring constantly
3. The mixture will thicken suddenly at gelatinization temperature (varies by source: potato at 60 degrees, cassava at 65 degrees, arrowroot at 70 degrees)
4. Continue cooking 3-5 minutes past thickening
5. Root starch pastes tend to be more translucent and elastic than grain pastes

Modifying Paste Properties

Basic starch paste can be adjusted for specific applications.

Increasing Tack (Stickiness)

• Add a small amount of honey or sugar syrup (5-10% by volume) to the warm paste
• Mix in a small quantity of warm bone glue solution (10-15% by volume) for significantly increased tack and bond strength

Improving Water Resistance

• Add alum (potassium aluminum sulfate) at about 2% by weight. Alum cross-links starch molecules, moderately improving moisture resistance
• Mix in a small amount of drying oil (linseed oil) at about 5% by volume. Shake or stir vigorously to emulsify. The oil component provides a water-resistant film as the paste dries

Extending Shelf Life

Plain starch paste spoils within 2-3 days at room temperature as mold and bacteria colonize the moist starch.

• Salt: Add 2-3% by weight. Effective for a few extra days
• Vinegar: Add 5% by volume. Acidity inhibits mold growth for up to a week
• Clove oil or camphor: A few drops per liter of paste. Traditional preservative used by bookbinders. If clove trees or camphor trees are available in your region
• Refrigeration/cold storage: Paste stored in a cool cellar lasts significantly longer, up to 1-2 weeks

Make Fresh

The best practice is to make only as much paste as you need for the day’s work. Starch and flour keep indefinitely when dry, so there is no advantage to making paste in advance and every disadvantage as it spoils.

Application Techniques

Paper and Fiber Bonding

Apply paste thinly and evenly with a flat brush. For paper, apply paste to one surface only, press together, and smooth from center outward to push air bubbles to the edges. Place under flat weights until dry (several hours to overnight). Paper bonded with starch paste will cockle (wrinkle) if paste is applied too thickly or unevenly.

Papier-Mache Construction

Starch paste is the traditional adhesive for papier-mache, a technique for building lightweight structures from layers of paper or cloth soaked in paste.

1. Tear paper or cloth into strips about 3-5 cm wide
2. Dip strips into thin paste, pulling between two fingers to remove excess
3. Layer strips over a form (clay, wood, or inflated animal bladder), overlapping edges
4. Apply 4-6 layers for a thin shell, 10-15 for a rigid structure
5. Allow to dry completely between every 3-4 layers to prevent mold
6. Once fully dry, the result is a lightweight, surprisingly strong shell

Light Woodworking

Starch paste can bond wood veneers, thin wood strips, and decorative inlays. Apply paste to both surfaces, press together firmly, and clamp for 24 hours. The bond is adequate for decorative work but should not be used for structural joints where bone glue or casein glue would be more appropriate.

Sealing and Sizing

Thin starch paste (diluted to watery consistency) applied to fabric or paper fills the pores and creates a smoother, less absorbent surface. This process, called “sizing,” is essential for preparing paper for writing with ink and for stiffening fabric for construction use.