Oil painting by Alfred Balding of Wisbech, showing the inside of the roller house of the mill at Parson Drove, near Wisbech, Cambridgeshire. Three crushing wheels are drawn by horses around a circular pan containing the woad leaves, while workers knead the crushed leaves into balls and carry these to the drying ranges outside. The mill was demolished in 1914. Woad is a cruciferous (formed from four equal petals, arranged croswide) plant yielding a blue dye which was widely cultivated until the end of the Middle Ages. Now rare, it has been superseded by the use of indigo dye.
© Science Museum / Science & Society Picture Library