Dyeing Scarlet with Lac — India's Ancient Insect Dye and the Source of Shellac

Use 30-50% WOF of seed lac for a deep scarlet. For 100 g of wool, weigh out 30-50 g. Lac is sold in two main forms: stick lac (raw lac scraped from branches, containing twigs and insect debris) and seed lac (stick lac washed and filtered into clean granules). Seed lac is easier to work with for dyeing. The granules are dark reddish-brown and brittle. Higher quality seed lac is darker — pale or yellowish lac has had more dye already removed during shellac processing.

Place the seed lac in a pot with 4 litres of warm water and soak overnight (8-12 hours). The water dissolves the laccaic acid dye from the resin matrix — the liquid will turn a deep, murky red during soaking. The resin itself does not dissolve in water (it requires alcohol to become shellac), so the dye separates cleanly from the resin during this soak. Stir occasionally to break up any clumps.

Bring the pot to a gentle simmer (80-85°C) and hold for 60 minutes. Stir occasionally. The liquid will deepen to an intense, dark red — nearly opaque. The heat helps extract the remaining laccaic acid that the cold soak did not release. Do not boil vigorously — excessive heat can degrade the colour. After simmering, the lac granules will be pale and waxy, having surrendered their dye to the water.

Strain the dye liquor through a fine mesh strainer into a clean pot. The spent lac resin (now pale and waxy) can be saved — it still contains the shellac polymer and can be dissolved in denatured alcohol to make a usable shellac finish for woodworking. The strained dye liquor should be a deep, clear red. Add 6 g of cream of tartar to brighten the scarlet and improve dye uptake.

Pre-wet the alum-mordanted wool, squeeze out excess, and lower it into the lac dye bath at room temperature. Slowly raise to 85°C over 30 minutes, then hold for a full 60 minutes. Turn gently every 10 minutes. Lac dye bonds well to alum-mordanted protein fibres — the laccaic acid forms a stable complex with aluminium ions. The bath will gradually pale as the wool absorbs the pigment.

Turn off the heat and let the wool cool in the dye bath overnight. Remove the next day, squeeze gently, and rinse in lukewarm water until the runoff is mostly clear. The final colour is a warm, rich scarlet — distinctly warmer than cochineal crimson, with an almost coppery glow that is characteristic of lac. On silk, lac produces an even more brilliant result — the fibre's natural sheen amplifies the warm red. Lac red has good washfastness and moderate-to-good lightfastness. Dry in shade.

Lac is the only dye material that simultaneously produces two entirely different commercial products: a textile dye and a polymer finish. The lac insect secretes the resin to protect its colony — a biological varnish. Inside the resin, the red pigment laccaic acid serves as a UV protectant. When a dyer extracts the dye with water, the remaining resin can be dissolved in alcohol to make shellac — the same finish used on antique furniture, French-polished pianos, and pharmaceutical pill coatings. This dual harvest made lac one of the most economically important insect products in human history, rivalling honey and silk.