Dyeing with Henna — The Lawsone Pigment That Colours Fibre, Skin, and Hair

Use 50-100% WOF of henna leaf powder. For 100 g of wool, weigh out 50-100 g of powder. Use body-art quality (BAQ) henna powder — this is finely ground from fresh leaves with high lawsone content. Avoid compound hennas or henna products marketed for hair that contain metallic salts or synthetic dyes. True henna powder is a fine, green-brown powder that smells earthy and herbaceous. The fresher the powder, the higher the lawsone content and the stronger the dye.

Mix the henna powder with enough warm water (40°C) to form a thick paste — roughly the consistency of yoghurt. Add 2 tablespoons of white vinegar or lemon juice to lower the pH to around 5.0-5.5. Stir until smooth and cover with plastic wrap. Let the paste rest at room temperature for 8-12 hours. This rest period is critical — lawsone releases slowly from the cell walls of the powdered leaves. The paste will darken from green-brown to a deep reddish-brown as lawsone oxidises, indicating dye release is complete.

After the overnight rest, add the henna paste to 4 litres of warm water in the dye pot and stir vigorously until the paste is fully dissolved. The water will turn a dark brownish-red. Some fine sediment is normal — henna powder does not dissolve completely. For the cleanest results, strain through muslin cloth to remove the coarsest plant particles, though many dyers leave the sediment in and strain after dyeing instead.

Bring the dye bath to 80°C and hold for 30 minutes. Do not boil — lawsone degrades above 90°C. This simmering step completes the extraction of any remaining lawsone from the plant particles and activates the dye. The liquid will darken further to a deep reddish-brown. Stir occasionally to prevent the sediment from settling and scorching on the bottom of the pot.

Pre-wet the alum-mordanted wool in lukewarm water for 15 minutes. Lower the wool into the henna dye bath at 60°C and raise slowly to 80°C. Hold for 60 minutes, turning the wool gently every 10 minutes. Henna dyes protein fibres through a Michael addition reaction — the lawsone molecule bonds covalently to the amino acids in wool. This makes the colour extremely permanent once set. The wool will turn a warm golden-brown to cinnamon, darker at higher concentrations. Without a mordant, the colour is slightly duller; alum produces the warmest, most vibrant tones.

Turn off the heat and let the wool cool in the dye bath overnight. The colour will continue to develop and deepen during cooling — henna needs time for the lawsone-fibre bond to fully mature. Remove, squeeze gently, and rinse in lukewarm water. Some plant sediment may cling to the yarn — rinse thoroughly until the water runs clear. The final colour is a warm golden-brown to rich cinnamon. Henna-dyed wool has exceptional washfastness — the colour is essentially permanent on protein fibres. Lightfastness is moderate to good. Dry in shade.