148 DTE 3. 



phere green ; but substances dipped into this deoxidized in- 

 digo, though at first they show a green color, become blue 

 when exposed to the air. 



Indigo, it is well known, may be dissolved in sulphuric 

 acid without changing color. Blues dyed with this solution 

 are known as Saxon-blues ; they are less permanent than 

 those derived from the green liquor. 



Indigo requires no mordant or basis to assist its combina- 

 tion with cloth. 



In calico-printing, indigo is ground with some deoxidizing 

 agent, wet with starch or gum to proper consistency, and 

 applied to the blocks which form the pattern ; the calico then 

 receives alternate baths of lime-water and a solution of sul- 

 phate of iron, until the indigo is sufficiently dissolved to give 

 a fixed color. 



RED DYES. 



Most of the substances used as red dyes require mordants 

 before they can be fixed on cloth. Logwood, safflower, archil, 

 Brazil-wood, cochineal, and madder, are substances largely 

 employed for red dyes, and are all adjective colors. 



Logwood is the wood of the Hcematoxylon Campeachianum, 

 which is found in Tropical America. A decoction of logwood 

 yields a fine red, with a violet or purple tint, which, if not 

 arrested by some agent, becomes in time yellowish, and final- 

 ly subsides into black. The violet color may be fixed by 

 alum, and a blue may be obtained by verdigris. But it is 

 for blacks that logwood is principally valued ; it imparts to 

 them great softness and depth of tone. 



Safflower is obtained from the leaves of the Carthamus 

 iinclorius. The coloring matter has little permanency. It 

 is familiarly known as a pink dye, spread on saucers. " The 

 fine rose-color of safflower," says Dr. Bancroft, " extracted 

 by crystallized soda, and precipitated by citric acid, and then 

 slowly dried in the shade, being afterwards finely ground 



