Woad

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{{Taxobox | color = lightgreen | name = Woad | image = Isatis tinctoria02.JPG | image_width = 240px | image_caption = Woad flowers | regnum = Plantae | divisio = Magnoliophyta | classis = Magnoliopsida | ordo = Brassicales | familia = Brassicaceae | genus = Isatis | species = I. tinctoria | binomial = Isatis tinctoria | binomial_authority = L. }}

Woad (or glastum) is the common name of the flowering plant Isatis tinctoria in the family Brassicaceae. It is occasionally known as Asp of Jerusalem. Woad is also the name of a blue dye produced from the plant. As for pronunciation, Woad rhymes with road.

Woad is native to the steppe and desert zones of the Caucasus, Central Asia to eastern Siberia and Western Asia (Hegi), but is now found in southeastern and some parts of Central Europe as well. It has been cultivated throughout Europe, especially in Western and southern Europe since ancient times.

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History of woad cultivation

Until the 19th century woad, together with indigo (Indigofera tinctoria, the source of indigo dye), dyer's knotweed (Polygonum tinctorium, from Japan and Korea) and Strobilanthes flaccidofolius from mainland Southeast Asia were the only blue dyes available in Europe and Asia.

The first archaeological finds of woad seeds date to the Neolithic and have been found in the French cave of l'Audoste, Bouches du Rhone (France). In the Iron Age settlement of the Heuneburg, Germany, impressions of the seeds have been found on pottery. The Hallstatt burials of Hochdorf and Hohmichele contained textiles dyed with woad. Julius Caesar tells us (de Bello Gallico) that the Britanni used to dye their bodies with woad (vitrum), which made them look terrible in battle. The Picts got their name (Latin Picti which means painted folk or possibly tattooed folk) from their practice of going into battle naked except for decorations made with woad war paint. (This has been commemorated in the humorous (modern) British song The Woad Ode.)

In addition to its use as a tattooing ink, it is believed that woad was used as an astringent. It produces quite a bit of scar tissue, but heals very quickly, and no blue is left behind. It may have been used specifically for closing battle wounds.

In Viking age levels at York, a dye shop with remains of both woad and madder dating from the 10th century have been excavated. In Medieval times, centres of woad–cultivation lay in Lincolnshire and Somerset in England, Gascogne, Normandy, the Somme, Toulouse and Britanny in France, Jülich, the Erfurt area in Thuringia in Germany and Piedmont and Tuscany in Italy. The citizens of the five Thuringian woad-towns of Erfurt, Gotha, Tennstedt, Arnstadt and Langensalza had their own charters. In Erfurt, the woad-traders gave the funds to found University Erfurt.

Medieval uses of the dye were not limited to textiles. For example, the illustrator of the Lindisfarne Gospels used a woad-based pigment for blue paint.

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Woad and indigo

Image:Waidklein.jpg The blue pigment in woad is the same as in indigo dye, but the concentration of the pigment is greater in indigo. With the European discovery of the seaway to India, great amounts of Indigo were imported. Laws were passed in some parts of Europe to protect the woad industry from the competition of the indigo trade, indigo was proclaimed to rot the yarns as well. With the development of a chemical process to synthesize the pigment, both the woad and natural indigo industries collapsed in the first years of the twentieth century. The last commercial harvest of woad until recent times occurred in 1932, in Lincolnshire, Britain.

In Germany, there are attempts to use woad to protect wood against decay without dangerous chemicals. Production is also increasing again in the UK for use in inks, particularly for inkjet printers, and dyes, as woad is biodegradable and safe in the environment, unlike many synthetic inks. Isatis tinctoria is viewed as an invasive species in parts of the United States.

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