248 DYEING 



itself. Logwood dye when used alone produces a reddish 

 brown color of no value either for beauty or permanence; 

 but if the fabric to be dyed is first mordanted with a solution 

 of alum and oxalic acid and is then immersed in a logwood 

 bath, it acquires a beautiful blue color. 



Moreover, since the color acquired depends upon the mor- 

 dant as well as upon the dye, it is often possible to obtain a 

 wide range of colors by varying the mordant used, the dye 

 remaining the same. For example, with alum and oxalic acid 

 as a mordant and logwood as a dye, blue is obtained; but 

 with a mordant of ferric sulphate and a dye of logwood, 

 blacks and grays result. Fabrics immersed directly in aliz- 

 arin acquire a reddish yellow tint ; when, however, they are 

 mordanted with certain aluminium compounds they acquire 

 a brilliant Turkey red, when mordanted with chromium com- 

 pounds, a maroon, and when mordanted with iron compounds, 

 the various shades of purple, lilac, and violet result. 



230. Color Designs in Cloth. It is thought that the earliest 

 attempts at making " fancy materials " consisted in painting 

 designs on a fabric by means of a brush. In more recent 

 times the design was cut in relief on hard wood, the relief 

 being then daubed with coloring matter and applied by hand 

 to successive portions of the cloth. The most modern method 

 of design-making is that of machine or roller printing. In 

 this, the relief blocks are replaced by engraved copper rolls 

 which rotate continuously and in the course of their rotation 

 automatically receive coloring matter on the engraved por- 

 tion. The cloth to be printed is then drawn uniformly over 

 the rotating roll, receiving color from the engraved design ; 

 in this way, the color pattern is automatically printed on 

 the cloth with perfect regularity. In cases where the fabrics 

 do not unite directly with the coloring matter, the design is 

 supplied with a mordant and the impression made on the 



