Indigotin Content of Woad

Abstract

BEFORE the general introduction of oriental indigo into Europe in the sixteenth century, woad, the product of the woad plant (Isatis tinctoria), was the only commercial source of a blue dye, and its production was the basis of a widespread and important industry. It was the result of a lengthy process involving the crushing of the leaves in specially designed mills, air drying the pulp obtained, grinding the dried material to a fine powder, wetting this, and allowing it to undergo spontaneous fermentation, during which it was kept moist and was frequently turned over. This last process took several weeks to complete, and the material became very hot while the fermentation was active. When cool, the mass was allowed to dry and, after re-grinding and sieving, constituted ‘finished woad’ ready for the dye-vat. The agricultural operations involved in growing the crop and details of the manufacturing process have been fully described by Hurry¹ and others.