Printing
A great variety of colored designs are produced on the loom by using different colored warp and filling yarns and different weaves, but in all these the designs are easily made only in somewhat rectangular patterns.
Block and Machine Printing
Print goods have doubtless evolved from the decoration of fabrics with the brush. Block printing was first used, the design being engraved in relief on blocks of wood. These are dipped in the colored paste, spread thinly, and applied to successive portions of the cloth by hand. These blocks are now replaced in the printing machine by engraved copper rolls, the design being such that it is repeated once or a number of times in each revolution of the cylinder. There is a printing roll for each color of the design. Sometimes both the background and the design are printed on the cloth, but the more common process is for the design only to be printed on the cloth which may be dyed afterwards. In the paste of the printed design there is some chemical which prevents the portions printed from taking the dye, consequently these remain white or a different color. This is called the “resist” process. Another process is to first dye the cloth and then print on some chemical which, when the calico is steamed, discharges the color. This is called the “discharge” process. Sometimes this weakens the goods in the places where the color has been discharged.
Fixing the Print
The color paste used for printing contains both the dye and the mordant. After the calico has been printed it is steamed to develop and fix the color, washed, sometimes very slightly bleached, to clear the whites, and usually given a sizing of starch or gum, and then pressed and dried by passing over slowly revolving, steam-heated drums.
In general print goods are not so fast to washing and to light as those that have been dyed in the regular way, although the better grades are reasonably fast.
Prints are sometimes made in imitation of the more costly gingham or other goods in which the color design is made in the weaving. It is easy to detect the imitation as the design of printed fabrics does not penetrate to the back of the cloth.
Warp Printing
Sometimes the warps are printed before the cloth is woven, thus giving very pretty indefinite designs, especially in silk.