Harvesting Lac Resin from Rain Trees — From Stick Lac to Shellac

The lac insect (Kerria lacca) is a tiny scale insect, about 1-2 mm long, that attaches itself to tree branches and secretes a protective resin coating. A single female produces approximately 300 times her body weight in resin. This resin is the raw material for shellac, lac dye, and traditional lacquerware.

Lac insects colonize many tree species in Cambodia. The most common hosts are the rain tree (Samanea saman), ber tree (Ziziphus mauritiana), and kusum tree (Schleichera oleosa). Look for branches covered in a reddish-brown crusty coating. The coating is the hardened resin secreted by thousands of lac insects.

Lac insects have two generations per year in tropical climates: the rainy season generation (June-October) and the dry season generation (October-March). Harvest when the resin is mature but before the new generation of crawlers emerges. The resin is ready when it is hard and deep reddish-brown, about 6 months after inoculation.

Before harvesting, identify branches where young insects are still emerging. Leave approximately 25-30% of encrusted branches untouched as brood lac. These will release crawlers that re-infest the tree for the next cycle. Sustainable harvesting ensures continuous production for years.

Using pruning shears or a sharp knife, cut branches that are heavily coated with lac resin. Cut at a point just below the encrusted section. The raw product at this stage is called stick lac because the resin is still attached to the sticks.

Use a blunt knife or flat scraper to chip the hardened lac resin off the branches. The resin comes off in irregular chunks and flakes. Collect into a clean container. From 5 kg of stick lac branches, expect about 1-2 kg of scraped raw lac.

Break the scraped lac into small pieces using a wooden mallet or mortar and pestle. Crush to approximately pea-sized fragments. Smaller pieces wash more effectively in the next step. Remove any large pieces of bark or wood mixed in.

Place the crushed lac in a large basin of cold water. Agitate and knead with your hands. The water turns deep red as the lac dye (laccaic acid) dissolves. This red dye was historically prized for dyeing silk and wool. Pour off the red water and save it if you want lac dye. Repeat washing 3-4 times until the water runs only faintly colored.

After washing out the dye, the remaining material contains resin mixed with insect bodies, sand, and wood fragments. Spread the wet lac on a flat surface and pick out visible debris. The resin pieces are translucent amber to dark red. Insect remains and wood are opaque.

Spread the cleaned lac in a thin layer on a mesh screen or cloth in the shade. Do not dry in direct sunlight as excessive heat can partially melt the resin. Drying takes 2-3 days. The dried product at this stage is called seed lac. It resembles small, irregular amber-colored grains.

Pass the dried seed lac through a coarse sieve to remove remaining wood splinters and large impurities. Then pass through a finer sieve to grade by particle size. Good seed lac is uniform in size and amber to garnet in color.

Weigh the final seed lac. From 5 kg of stick lac branches, expect approximately 500-800 g of seed lac. Quality seed lac is translucent, free of wood and insect debris, and dissolves readily in denatured alcohol (ethanol). The darker the color, the lower the grade. The lightest amber grades command the highest price.

Store seed lac in airtight containers in a cool, dark place. Seed lac has a long shelf life but degrades slowly over time as it polymerizes. Use within 1-2 years for best results. Seed lac dissolves in denatured alcohol to make liquid shellac for wood finishing, or can be melted and stretched into shellac sheets.