CALICO PRINTINe. 199 



water and cow-dung ; this, also, discharges such 

 parts of the mordant as are not properly fixed, 

 enough being still left to fix the dye. The cloth 

 is then rinsed in clear water. It is then dyed in 

 the usual manner. 



The principal dye-stuffs used by calico-printers 

 are indigo, madder, quercitron bark, and weld. 



After dyeing, the cloth is well washed, exposed 

 on the grass, and bleached ; by which all the parts 

 not touched by the mordant are restored to their 

 original whiteness. 



In this manner various colours may be given by 

 one dyeing, merely by varying the mordant. Thus, 

 if one pattern be printed with alum alone, a second 

 with a mixture of alum and iron liquor, a third 

 v.'ith iron liquor alone, and a fourth with iron li- 

 quor and galls, and the piece be afterwards dyed 

 with quercitron or weld, and the ground bleached 

 in the usual manner ; the first pattern will be pure 

 yellow, the second will be olive, the third of a dark 

 drab colour, and the fourth nearly black, while 

 the ground will be white. 



As indigo does not require any mordant, it is 

 applied at once, either by a pencil or by a block 

 and paste. But, as has been mentioned under dye- 

 ing, indigo will not combine with the cloth except 

 in its disoxygenated or green state ; and, if applied 

 thus by the pencil, it would return to the blue state 

 before it had time to fix upon the stuff. The in- 

 digo is, therefore, prepared by boiling with potash, 

 made caustic by quicklime, to which is added 

 orpiment for the disoxygenation of the indigo. 

 This solution is thickened with gum. It must be 

 excluded from the air, otherwise it would attract 

 oxygen and return to the blue or insoluble state. 

 Dr. Bancroft proposed substituting brown sugar 



o 4 . . 



