one encounters in 19th century dyers' books. The main purpose of these 

 ingredients was to combine them with indigo to reduce it and make it 

 soluble in alkali solutions; in this dissolved state indigo could be absorbed 

 by textile material. 



Bran and madder, by inducing fermentation, act as reducing agents. 

 Other chemical compounds (such as copperas) which also act as reducing 

 agents were frequently used. Indigo, in its reduced state, then is dissolved 

 in an alkali solution — usually made up of lime, potash, or soda in water. 



A typical and comparatively uncomplicated vat that Thomas Cooper 

 said was used by wool dyers of Pennsylvania and American back-country 

 dyers (1815, p. 45) is basically similar to the "Blue-Pot" recipe given in 

 the Dye Recipe section. Another dyer of the same period commented that 

 urine used as a fermentation-inducing ingredient in indigo dyeing had 

 been used with great success. Each individual dyer's procedures were 

 adapted to the amount of cloth dyed, frequency of dyeing, and the available 

 ingredients. Thus though the blue vat was often worked under primitive 

 conditions, 18th and 19th century professionals and home dyers alike 

 considered the complicated indigo-dyeing process as the basic method of 

 coloring textiles. 



Other Blue Dyes 



Although indigo was by far the most important dyestuff used throughout 

 18th- and 19th-century America, a few other blue dyestuflfs were employed 

 by professional clothiers and dyers. Among these were woad, chemic, and 

 Prussian blue. 



WOAD (Isatis tinctoria) 



Also known as pastel (Fr.); der (Farber) Waid (Ger.) 



Woad was well known long before the Dutch introduced East Indian 

 indigo into Europe late in the 16th century. During the 17th century, 

 indigo's value became more and more recognized in spite of determined 

 efforts by the guilds of the woad processors to limit its use. Woad was 

 probably the first blue dyestuff used in America, carried from their mother 

 country by the earliest colonizers. By 1700, however, indigo could be 

 obtained from the West Indies, and from that time woad's importance 

 diminished as indigo became more and more widely used. 



The woad vat was basically similar to the indigo vat, requiring care in 

 controlling the fermentation process by which the coloring agent was 

 reduced to its soluble form. According to many 19th-century American 

 dyers, great skill was required to develop the correct degree of fermentation 

 in the woad vat due to great quality differences in the raw material. Often 

 the experienced woad dyer's most valuable asset was his sensitive nose, 



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