Editing Isatis tinctoria (section)

==Woad and indigo==
[[File:Isatis tinctoria 003.JPG|thumb|upright=0.8|Indigo extracted from woad]]
{{Infobox color
| title=Celtic Blue
| hex=246bce
| spelling=colour
| source=[https://www.google.co.uk/search?q=celtic+blue&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi95M2Hz6bWAhXFvBoKHTzlDOQQ_AUICigB&biw=1024&bih=679#imgrc=u9QI8GmuiEZTzM: Internet]}}

The dye chemical extracted from woad is [[indigo dye|indigo]], the same dye extracted from "true indigo", ''[[Indigofera tinctoria]]'', but in a lower concentration.  Following the [[Portuguese discovery of the sea route to India]] by the navigator [[Vasco da Gama]] in 1498, great amounts of indigo were imported from Asia. Laws were passed in some parts of Europe to protect the woad industry from the competition of the indigo trade. It was proclaimed that indigo caused yarns to rot.<ref>{{cite magazine |url=http://www.gutenberg.org/files/13242/13242-8.txt |magazine=Lippincott's Magazine of Popular Literature and Science |volume=17 |issue=100 |date=April 1876 |title=Sketches of India |via=Project Gutenberg}}</ref> This prohibition was repeated in 1594 and again in 1603.<ref>D G Schreber, ''Historische, physische und economische Beschreibung des Waidtes'', 1752, the appendix; Thorpe JF and Ingold CK, 1923, ''Synthetic colouring matters - vat colours'' (London: Longmans, Green), p. 23</ref> In France, [[Henry IV of France|Henry IV]], in an edict of 1609, forbade under pain of death the use of "the false and pernicious Indian drug".<ref>{{cite book |first=Édouard |last=Foucaud |editor-last=Frost |editor-first=John |title=The book of illustrious mechanics |publisher=D. Appleton |year=1846 |page=[https://archive.org/details/bookillustrious00foucgoog/page/n246 236] |url=https://archive.org/details/bookillustrious00foucgoog}}</ref>

With the development of a chemical process to [[Indigo dye#Era of synthetic indigo|synthesize]] the pigment, both the woad and natural indigo industries collapsed in the first years of the 20th century. The last commercial harvest of woad until recent times occurred in 1932, in [[Lincolnshire]], Britain. Small amounts of woad are now grown in the UK and France to supply craft dyers.<ref>{{cite web|first=Chris|last=Cooksey |url-status=dead |url=http://www.chriscooksey.demon.co.uk/indigo/woad.html |title=Indigo - woad |publisher=Chris Cooksey |access-date=2012-10-09 |archive-date=2012-02-19 |archive-url=https://web.archive.org/web/20120219063526/http://www.chriscooksey.demon.co.uk/indigo/woad.html }}</ref> The classic book about woad is ''The Woad Plant and its Dye''<ref>{{cite book|last=Hurry|first=Jamieson Boyd|editor-last= Milford|editor-first=Humphrey Sumner|editor-link=Humphrey Sumner Milford |title=The Woad Plant and its Dye|year=1930|publisher=[[Oxford University Press]] |location=London|isbn=9780678007792|quote=isbn 1973 reprint |oclc=702743|via=[[Archive.org]] |url=https://archive.org/details/woadplantitsdye0000unse/page/n7/mode/2up |url-access=registration }}</ref> by J. B. Hurry, Oxford University Press of 1930, which contains an extensive bibliography.<ref>{{cite web |url=http://www.chriscooksey.demon.co.uk/indigo/jbhurry.html |title=J B Hurry's woad bibliography |publisher=Chris Cooksey |access-date=2012-10-09 |archive-date=2012-04-16 |url-status=dead |archive-url=https://web.archive.org/web/20120416121530/http://www.chriscooksey.demon.co.uk/indigo/jbhurry.html }}</ref>

A method for producing blue dye from woad is described in ''The History of Woad and the Medieval Woad Vat'' (1998) {{ISBN|0-9534133-0-6}}.<ref>{{cite web
| url         = http://www.imperial-purple.com/dyes1.html
| title         = Historic Dyes Series No. 1 - The History of Woad and the Medieval Woad Vat by John Edmonds
| access-date         = 28 January 2011
| publisher         = unknown
| archive-url         = https://web.archive.org/web/20100825034609/http://www.imperial-purple.com/dyes1.html
| archive-date         = 25 August 2010
| url-status         = usurped
}}</ref>

Woad is biodegradable and safe in the environment. In Germany, there have been attempts to use it to protect wood against decay without applying dangerous chemicals.<ref>{{Cite patent |status=patent |country=EP |number=1223198A1 |fdate=2001-12-11 |invent1=Hans-Martin Dr. Dahse |invent2=Klausjürgen Dr. Dornberger |invent3=Albrecht Feige |invent4=Dr. Matthias Hilliger, Prof. Waldemar Künkel, Prof. Axel Stelzner |title=Process for the development of an environmentally desirable raw material based on woad (isatis tinctoria L.) |url=https://patents.google.com/patent/EP1223198A1/en |pridate=2000-12-13 |gdate=2004-02-25}}</ref> Production of woad is increasing in the UK for use in [[ink]]s, particularly for [[inkjet printer]]s, and dyes.