DYEING. 185 



In dyeing, the water employed should be as 

 pure as possible, and the exact temperature in each 

 process should be attended to. The dye-houses 

 should be spacious, light, and airy, and cleanness is 

 essentially necessary, The stuffs are supported in 

 the cauldrons, or baths, by proper apparatus, and 

 are drawn through them by a winch, or reel, 



Of Dyeing Red. 



The colouring matters employed for dyeing red 

 are cochineal, kermes, madder, lac, Brazil-wood, 

 logwood, and carthamus. Cochineal is a species 

 of insect (the coccus cacti, Lin.) brought from 

 America. The decoction of it affords a very bright 

 crimson colour, inclining to violet. When alum 

 is added to this decoction, it combines with its 

 colouring matter, and forms a red precipitate. 

 Muriate of tin gives a still more beautiful colour. 



Kermes is also an insect found in several parts 

 of Asia, and the south of Europe, which furnishes 

 a red dye, by some thought not inferior to cochi- 

 neal, but which has not been so much used since 

 the introduction of the latter. 



Madder is the root of a plant (rubia tinctorium, 

 Lin.) The colouring matter of madder is extracted 

 by water, either cold or hot, and precipitates of 

 various shades of red may be obtained by alum, 

 chalk, acetate of lead, and muriate of tin. 



Lac is a colouring matter of animal origin, pro- 

 duced in the East Indies, from the coccus lacca, a 

 small winged insect. This insect forms cells for 

 its young, as regular as the honey-comb, but diffe- 

 rently arranged ; and the lac is procured from the 

 substance of which these cells are made. The whole 

 matter of thesq cells is called stick lac ; when the 



