ON WOAD AS A PREHISTOETC PIGMENT. 



85 



in giving accounts of Woad manufacture, and stating that this plant was 

 formerly used for dyeing cloth blue, but has now been superseded by 

 indigo. Indigo was introduced into Europe as a commercial article in 

 the sixteenth century, but Woad is still grown and manufactured in the 

 above-named districts, so that although superseded by indigo as a dye, 

 the manufacture of it is an industry which dies hard. Just one hundred 

 years ago, when Arthur Young * visited Lincolnshire, its use was declining, 

 and he speaks of it as if a few more growers would even then hopelessly 

 swamp the market. In the tenacity with which this industry clings to 

 life it resembles the moribund flint- knapping still carried on at Brandon, 

 where one may even to-day watch the manufacture of gun flints. It is 

 clear, then, that Woad still has a use in dyeing, but that use is iiot the 

 yielding of a blue dye ; in fact, it is its peculiar use which has caused its 

 coerulescent property to be lost sight of so completely. It is used for the 

 purpose of setting up a fermentation in the indigo vat, whereby the indigo 

 is rendered soluble. Curiously enough, this cumbersome and expensive 

 mode of dyeing yields such excellent results that a " woaded cloth " has 

 come to mean any particularly " fast cloth," whether it be dyed by Woad 

 or not. These W^oad vats are difficult to manage, but the articles dyed in 

 them will stand rain and sunshine, salt spray and sea air better than any 

 others. The Woad grower's aim is to produce an article containing the 

 maximum amount of fermentable material, regardless of the quantity of 

 colouring matter. But it was not always so. During the early part of the 

 nineteenth century there still survived a proverbial saying in East Anglia 

 which can yet be remembered by the older generation, based on the 

 colouring property of Woad, viz. to speak of an object being " As blue 

 as Wad." In France, during the long war which terminated at the 

 battle of Waterloo, so great was the difficulty experienced in getting indigo 

 into the country that the Government offered a substantial reward for 

 the discovery of any blue dye capable of being produced in the climate of 

 Europe, and which would prove an effective substitute for indigo. Atten- 

 tion was naturally directed to Woad, and various treatises upon its culture 

 and the best methods of extracting indigo from it appeared. In one of 

 these Giobert,t a professor of chemistry at Turin, gives several methods 

 for its extraction. From the tone in which he writes one would conclude 

 this to be a very simple matter. However satisfactory these processes 

 may have been in France and Italy, they have not proved so in my hands. 

 Indeed, after many trials, I came to the conclusion that indigo was now 

 absent from our Woad. In 1855 Dr. E. Schunck showed that indigo 

 does not exist as such in Woad, neither as the soluble indigo-white 

 (C16H12N2O2), nor the insoluble indigo-blue (Ci6H,4N20.2), but that it 

 was produced by the oxidation of a peculiar body to which he applied the 

 name of indican (C26H3,NO- 7). Indican can be extracted from Woad 

 by various more or less complicated processes, of which the details are 

 given in Dr. Schunck's paper.J It is a very unstable body, which by the 

 action of acids passes into indigo-blue. 



* Young, Arthur, A General Vieio of tlic Agriculture of Lincolnshire, 8vo. 1799. 



t Giobert, M., TraiU sur le Pastel, Paris, 1813 ; De Puymaurin Sur l<: Pastel, sa 

 Culture, ct les Moijens d'en retirer V Indigo, 1810. 



X Schunck, Dr., "On the Formation of Indigo-Blue," Philosophical Maga::i)u\ 

 Aug. 1855, vol. X. p. 73. 



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