1835.] 



Calico- Printing . 



15 



cloth to the action of madder, suspended in water. In con- 

 sequence of the very sparing solubility of the colouring 

 matter of that root, and the difficulty of applying it equally 

 to all parts of the cloth, the process requires to be con- 

 ducted slowly, and the heat to be very gradually raised. The 

 purest portion of the colouring matter being first given out 

 by the madder, the degree of heat is varied, according to 

 the fineness of the colour we desire to obtain. 



After dyeing, those parts of the cloth intended to be 

 white, are always, more or less, tinged with the madder, 

 and much pains are necessary to restore their purity. For 

 this purpose, boiling with bran, or with soap, exposure to 

 light upon the grass, clearing with chloride of lime, or 

 other substances, which have the property of dissolving or 

 destroying this colouring matter, with repeated wash- 

 ings in cold water, are all resorted to according to 

 circumstances. And several of these operations have the 

 additional effect of brightening the red, by abstracting a 

 brownish matter, which always combines with the alumina, 

 at the same time with the red colouring matter. 



2. Madder Purple. — The iron mor- 

 dant thickened in the same way as 

 the alum mordant, is similarly ap- 

 plied. The cloth is then exposed to ..■ I 

 the air for a few days, and the iron | 

 fixes itself on the cloth in proportion 

 as it becomes peroxidized . The piece 

 is then cleaned and washed as described lrrxne last proc 

 dyed in madder, and cleared in the same way as in the red 

 just described. The depth of the purple depends upon the 

 strength of the iron mordant. If its specific gravity be as 

 high as 1-04, it forms a black, as appears in the three suc- 

 ceeding specimens. \i x x {-'jM 



3. This piece shows two different 

 shades of purple, or rather black 

 and purple along with red, all dyed 

 at once. The black and purple are 

 printed together by the cylinder ma- 

 chine, with two copper rollers, and 

 the purple is printed afterwards by 

 the block. 



