Woad (colorant)

A natural dark blue dye obtained from the leaves of the biennial Isatis tinctoria plant. It was cultivated since early times as a textile dye in England, France, Greece, Italy, Egypt, and China, and was used as a painting pigment in the Middle Ages. It is chemically and in color similar to indigo. To produce the colorant, the plant leaves were cut, dried, and rolled into balls (woad balls) to age for about one month. Then the balls were crushed to a fine powder, sprinkled with water, and piled in heaps for fermentation. The blue color deepened with the age of the plant, ranging from a light blue in young leaves to a dark bluish black in fully ripe leaves.