Dyeing Purple with Alkanet Root — The Mediterranean Pigment of Antiquity

Use 100-150% WOF of dried alkanet root. For 100 g of wool, weigh out 100-150 g of dried root. Alkanet root is sold as dried, chopped root pieces that are dark reddish-brown to almost black on the outside. Cut or break any large pieces into 1-2 cm fragments to increase surface area for extraction. The root will stain your fingers purple-red on handling — wear gloves if this is a concern.

Place the chopped roots in a dye pot with 4 litres of warm water. Add 5 g of sodium carbonate (soda ash) and stir to dissolve. The soda ash raises the pH to approximately 9-10, which is necessary because alkannin is poorly soluble in neutral or acidic water. In alkaline solution, the pigment dissolves and the water will turn a deep reddish-purple within hours. Soak for 8-12 hours. By morning, the liquid should be a dark, opaque purple-red.

Bring the alkaline root bath to a gentle simmer (75-80°C) and hold for 60 minutes. Do not boil — high temperatures degrade alkannin and shift the colour toward muddy brown. Stir occasionally. The liquid will deepen to an intensely dark purple-red. Alkanet roots extract slowly compared to flower or leaf dyes — the full 60 minutes of simmering is needed to draw out the pigment from the dense root tissue.

Strain the dye liquor through a fine mesh strainer into a clean pot. Press the roots to extract all remaining purple liquid. Root fragments can stain wool unevenly if left in contact — strain thoroughly. The strained liquid should be a deep, clear purple-red. At this stage, the alkaline pH means the colour appears very red. When the wool enters and the pH shifts slightly during dyeing, the colour will lean more toward purple and mauve on the fibre.

Pre-wet the alum-mordanted wool in lukewarm water for 15 minutes. Lower it into the alkanet dye bath at room temperature and slowly raise to 75-80°C. Hold for 60 minutes, turning gently every 10 minutes. The alum mordant interacts with alkannin to produce the characteristic purple-grey to mauve shades. The colour develops slowly — do not rush this step. Alkanet colours are inherently muted and complex rather than vivid. Expect a soft, dusky purple-mauve rather than a bright violet.

Turn off the heat and leave the wool in the dye bath overnight. The extended cooling allows the alkannin-alum complex to stabilise fully on the fibre. Remove, squeeze gently, and rinse in lukewarm water. The rinse water will be faintly pink — some washoff is normal with alkanet. The final colour is a soft, dusky mauve to purple-grey — one of the most subtle and sophisticated colours in the natural dyer's palette. Lightfastness is moderate. Dry in shade.