REMARKS ON DYEING. 55 



in common lan2;uage. A substantive color is therefore one that 

 will act of itself ; an adjective color requires the addition of some 

 other body. Those substances used along with adjective dyes have 

 been called mort/an/s, from the idea that they 6//e in the color; 

 they are chiefly alum, and some of the metallic salts, particularly 

 those of tin, occasionally also those of mercury, lead, and iron. 

 But these, besides fixing the dye, also change its color, and hence 

 their tise in procuring different colors from the same dye-stutf, as 

 the remarks on the properties of coloring matters show, these be- 

 ing changed by the addition of the ditferent agents mentioned. 



" From what has now been said, it is evident that there are two 

 modes of dyeing, either by substantive or adjective colors. When 

 the attraction between the cloth and the color is strong, all that is 

 necessary is, to soak it in the infusion of the dye-stutf, by v.'hich 

 the color is imparted, and tixed. But when the attraction is weak, 

 it must be tirst saturated with a mord.rit, and then with the color- 

 ing matter. Of course the mordant must vary according to the 

 nature of the dye. 



" There is still another method altogether different from those 

 mentioned ; it is not by using the dye already prepared, but by 

 combining the cloth with substances which act on each other, and 

 strike the color required ; and in this way also the coloring matter 

 becomes tixed. Thus, a piece of cloth can be dyed black, by soak- 

 ing it in a mixture of infusion of nutgails and green vitriol, the 

 substances used in making ink, and which form a black color ; but 

 in this case, the color is not tixed. If, however, the cloth be pre- 

 viously imjiiersed in the infusion, and after being dried, be put into 

 the solution of green vitriol, the same black is produced, the 

 chemical action taking place on the cloth, as when the solutions 

 themselves were mixed, and the color is thus rendered fixed. In 

 this way a great variety of colors may be produced. xMany of 

 these have been already described, when treating of the properties 

 of the metals. In dyeing the compound colors, as green, this is 

 generally done by giving to the cloth a blue color, and afterwards 

 soaking it in a yellow infusion. Thus, by dyeing it with indigo, it 

 beco.nes blue, and by putting it into an alum bath, and then into 

 quercitron, the yellow of the latter and the blue together, form 

 green. 



" As mordants are used to fix color on cloth, it is evident, that 

 if, instead of being applied to the whole, certain parts only are 

 covered with it, the color, though communicated to the whole, will 

 be fixed only on those parts saturated with the mordant , and that 

 this is the case is easily shewn, by making some traces with the 

 infusion of nutgails on cloth, and allowing it to dry, and then put- 

 ting it into a solution of green vitriol ; the color, on the traces 

 only, will be durable. Hence the mode of applying a pattern on a 

 white or colored ground, and which is called calico printings from 

 its being usually done on calico. 



" Two mordants are in general use by the calico printers, alu- 

 mina and iron in union with acetic acid, or acid of vinegar. The 



