Bleaching Kiers
Printing Process
The printing process is a very old one, and was employed centuries ago in China and India, where natives used to impregnate cloth with colored designs by pounding small wooden blocks carved and filled with color on its surface. The modern printing machine has a series of copper rollers in which the design to be printed is etched or sunk. Under each roller where it is fixed in the printing press is a trough filled with the particular coloring matter which that roller is to print on the cloth. As the mechanism revolves the roller is constantly supplied with new color, which is scraped off its surface except where the sunken design holds it, by a knife, called the doctor. If the design calls for six colors there will be six rollers at work, and so on up to fourteen colors at a single run through the press.
Engraving
An infinite number of designs are printed, and the method of getting them etched on the copper roller is a fascinating one. A zinc plate is carved by hand on a greatly enlarged scale from the original sketch, and from this plate the girls who operate the pantograph machines transfer the outlines of each color on to the copper rollers.
Printing Machine
The Pantograph
When the roller is placed in the pantograph it is coated with varnish. As the girl traces the outlines of the design on her zinc plate with a little pointer, she presses a treddle which brings a number of little diamond points in contact with the roller. Each one of these points cuts through the varnish, reproducing the design in its original size. There will be as many points as the number of times the design is repeated across the roller. When the roller is finished it is given a bath in nitric acid which will eat into the copper where the varnish has been cut away, thus sinking the design so that it will hold color.
