Shellac

Part of Rubber and Polymers

Harvesting and processing shellac — a natural polymer resin produced by lac insects — for use as a coating, adhesive, and sealant.

Why This Matters

Shellac is one of nature’s most remarkable polymers. It is the only commercial natural resin of animal origin, secreted by the lac insect (Kerria lacca) as a protective coating on tree branches. Unlike most natural polymers, shellac is thermoplastic — it softens with heat and hardens when cooled, and can be remelted and reshaped repeatedly. It also dissolves readily in alcohol, making it easy to apply as a coating.

For a rebuilding civilization, shellac fills roles that are otherwise difficult to achieve without petroleum-based plastics. It creates a hard, glossy, waterproof, food-safe coating for wood. It serves as an electrical insulator. It bonds materials as a thermoplastic adhesive. It can be molded into small rigid objects (the first phonograph records were shellac). It seals surfaces against moisture and creates a smooth, paintable primer on porous materials.

Shellac production requires lac insects, which are found in tropical and subtropical Asia. If your rebuilding community is in a region where these insects exist (or where they can be introduced to suitable host trees), shellac becomes an invaluable resource. Even if you lack the insects, understanding shellac’s properties helps you identify substitute resins from other sources.

The Lac Insect Life Cycle

Biology

The female lac insect (Kerria lacca) settles on a tree branch, inserts her mouthparts into the bark to feed on sap, and secretes a resinous coating (lac) that eventually encases her completely. Thousands of insects settle together, creating a continuous resinous crust over entire branches. This crust is “sticklac” — the raw material for shellac.

Host Trees

Lac insects thrive on specific tree species:

Tree	Region	Suitability
Kusum (Schleichera oleosa)	South/Southeast Asia	Excellent — produces high-quality lac
Palas (Butea monosperma)	India, Myanmar	Very good
Ber (Ziziphus mauritiana)	Tropical Asia, Africa	Good
Fig species (Ficus)	Pantropical	Moderate
Acacia species	Tropical worldwide	Moderate

Cultivation Cycle

1. Inoculation: Tie small branches bearing live lac insects (“broodlac”) onto a suitable host tree in spring or early monsoon
2. Growth: Insects settle, feed, and begin secreting lac within days
3. Maturation: Over 4-6 months, the resin crust builds up to 3-6 mm thick
4. Harvest: Scrape or cut the encrusted branches before the next generation of insects emerges (timing is critical — harvest too late and you lose the insects)
5. Reserve broodlac: Always leave some encrusted branches unharvested to provide insects for the next generation

Sustainable harvest

Never harvest more than two-thirds of the lac from a tree in one cycle. The remaining third provides broodlac for the next generation. Overharvesting collapses the insect population.

Processing Raw Lac

Step 1: Sticklac Preparation

1. Scrape the resin crust from branches using a blunt knife or wooden scraper
2. Crush the scraped material into small pieces
3. Soak in water for several hours — this dissolves the reddish dye (lac dye, a valuable byproduct)
4. Agitate and wash repeatedly until the water runs clear
5. The remaining material is cleaned sticklac — a mix of resin, insect residue, and wood fragments

Step 2: Seedlac Production

1. Dry the washed sticklac thoroughly in shade
2. Winnow or sieve to remove large wood fragments and insect parts
3. The cleaned, dried granular material is “seedlac”
4. Seedlac can be used directly for some applications (mixed into alcohol as a rough shellac solution)

Step 3: Shellac Production

To produce refined shellac from seedlac:

Heat Method (Traditional):

1. Place seedlac in a long, narrow cotton cloth bag
2. Hold one end of the bag near a charcoal fire, warming the resin until it softens
3. Twist the bag to squeeze molten resin through the cloth, filtering out impurities
4. Scrape the extruded resin onto a smooth, cool surface (a polished stone or wet ceramic)
5. While still warm and pliable, stretch the resin into thin sheets
6. The sheets cool into hard, brittle flakes — this is shellac

Alcohol Dissolution Method:

1. Dissolve seedlac in ethanol (grain alcohol, at least 90% concentration)
2. Use approximately 200 grams of seedlac per liter of alcohol
3. Stir or shake daily for 2-3 days until fully dissolved
4. Filter through fine cloth to remove undissolved impurities
5. The resulting solution is ready to use as a coating
6. Alternatively, pour onto a flat surface and let the alcohol evaporate to recover solid shellac

Applications

Wood Finishing

Shellac produces a beautiful, food-safe, water-resistant finish on wood.

French Polish Technique:

1. Make a “rubber” pad by wrapping cotton or wool in a smooth linen cloth
2. Charge the pad with shellac solution (dissolved in alcohol)
3. Add a single drop of oil (linseed or olive) to the pad surface as a lubricant
4. Rub the pad over the wood surface in small circular motions
5. The shellac builds up in thin layers, each melting slightly into the previous one
6. Continue building coats until the desired gloss is achieved (typically 20-40 passes)
7. Finish with straight strokes along the wood grain
8. The result is a deep, lustrous finish that was the standard for fine furniture for centuries

Adhesive and Sealant

Shellac’s thermoplastic property makes it an excellent adhesive:

1. Heat shellac flakes until they soften and become sticky
2. Apply to the joint surfaces while hot
3. Press together and hold until cooled
4. The bond is strong for rigid joints but brittle under impact
5. Reheating allows repositioning or disassembly

Sealing applications:

• Sealing cork stoppers in bottles
• Waterproofing knots and nail holes in wood
• Filling small cracks and gaps
• Sealing the ends of cut rope to prevent fraying

Electrical Insulation

Before modern plastics, shellac was the primary electrical insulator:

• Coat wire with shellac solution to prevent short circuits
• Shellac-soaked paper or cloth becomes rigid insulating board
• Impregnate coil windings with shellac to prevent wire movement and arcing
• Breakdown voltage: approximately 30 kV/mm (comparable to many modern plastics)

Molding and Casting

Shellac can be molded into rigid objects:

1. Grind shellac into powder
2. Mix with fillers (wood flour, chalk, cotton fiber) at approximately 50% filler by weight
3. Heat the mixture until the shellac melts and binds the filler
4. Press into molds under firm hand pressure
5. Allow to cool — the result is a hard, machinable material
6. Can be drilled, filed, sanded, and polished

Early plastic

Shellac mixed with wood flour was one of the first “plastics” — used for buttons, boxes, electrical fittings, and even denture bases before synthetic plastics were invented.

Lac Dye

The red-purple dye washed from sticklac is a valuable secondary product:

• One of the oldest known dyes — used in India for over 3,000 years
• Excellent colorfastness on wool and silk
• Can also be used as a wood stain when dissolved in alcohol
• The dye contains laccaic acid — mordant with alum for bright red on textiles

Shellac Properties Reference

Property	Value
Melting point	75-80C (softens at 65C)
Soluble in	Ethanol, methanol, alkaline water
Insoluble in	Water (once cured), oils, turpentine
Food safety	Safe — used on candy, fruit coatings, and pharmaceutical tablets
Shelf life (dry)	Indefinite if kept dry and cool
Shelf life (dissolved)	6-12 months — degrades in solution
Color range	Blonde (lightest) to dark garnet (darkest)

Substitutes When Lac Insects Are Unavailable

If you cannot obtain lac insects, similar (though inferior) results can be achieved with:

• Pine rosin: Dissolved in alcohol, creates a serviceable coating but less durable and not food-safe
• Dammar resin: From dipterocarp trees in Southeast Asia, similar clarity to shellac
• Beeswax-rosin blend: Melted together, creates a waterproof coating for wood
• Birch bark tar: Dark but effective waterproof sealant for rough applications
• Casein (milk protein) finish: Mix dried milk curite with lime for a water-resistant paint/sealant

None of these fully replaces shellac’s unique combination of properties — thermoplastic behavior, alcohol solubility, food safety, and high-gloss finish. If your region supports lac insect cultivation, it is worth the effort to establish and maintain a colony.