Dyeing with Logwood — The Colonial-Era Route to Natural Black and Purple

Use 50-100% WOF of logwood chips for a deep colour. For 100 g of wool: 50 g gives a medium purple or grey; 100 g gives deep purple or near-black depending on the mordant. Logwood is sold as small chips or shavings of the dark reddish-brown heartwood. The chips should smell faintly sweet and woody. Higher quality chips are darker — pale or whitish chips come from the sapwood, which contains much less haematoxylin.

Place the logwood chips in a pot with about 4 litres of warm water and soak overnight (8-12 hours). The chips swell and begin releasing haematoxylin — the water will turn a deep, inky purple-red. This cold extraction draws out the dye gently and completely. Logwood that is simmered without pre-soaking releases less colour and wastes material. The soaking liquid will darken dramatically overnight — by morning it looks like dark grape juice.

Bring the pot to a gentle simmer (80-85°C — logwood should not be boiled vigorously) and hold for 60 minutes. Stir occasionally. The liquid will deepen to an intensely dark purple, nearly opaque. After simmering, the chips will be pale and spent. Logwood releases haematoxylin in waves — the first extraction is the strongest, but a second simmer of the same chips in fresh water yields a useful paler bath.

Strain the dye liquor through a fine mesh strainer or muslin cloth into a clean pot. The strained liquid is an intensely dark purple-black — one of the most concentrated natural dye baths you will encounter. Logwood chips left in contact with the wool during dyeing can cause dark spots, so strain thoroughly. Save the spent chips for a second, weaker extraction if desired.

For violet-purple: use alum-mordanted wool. Pre-wet the wool, lower it into the logwood bath at room temperature, and slowly raise to 80°C over 30 minutes. Hold at 80°C for 45 minutes, turning gently. The wool absorbs the haematein-aluminium complex, producing a rich violet-purple — the colour of amethyst. This is the classic logwood purple that was used for ecclesiastical vestments, academic robes, and luxury fabrics.

For natural black: after dyeing with logwood on alum-mordanted wool, give the purple-dyed wool a brief iron afterbath. Dissolve 2 g of ferrous sulfate in 2 litres of warm water. Submerge the logwood-purple wool for 10-15 minutes. The iron reacts with the haematein, darkening the purple to deep charcoal grey and ultimately to near-black. Rinse immediately when the desired depth is reached. This logwood + iron combination was the standard method for achieving natural black in European and American textiles from the 1600s through the 1800s.

Cool the dyed wool in the bath for several hours (or overnight for the richest colour), then rinse in lukewarm water until the runoff is mostly clear. Logwood purple and black have good washfastness but only moderate lightfastness — they will fade slowly in prolonged direct sunlight. For items that will see sun exposure, overdye with a second dip after several months to refresh the colour. Dry in shade. The final result is one of the most satisfying achievements in natural dyeing: true black from wood, water, and iron.