an offset printing form with the printing elements recessed in comparison with the white (nonprinting) elements. Originally, this term was used to designate forms made by the positive method of copying on aluminum or zinc plates, during which the recessing was done (to 0.001-0.002 mm) by chemically etching the metal on the printing elements. The forms for deep offset are also made on bimetallic plates, on which the printing elements are formed on a surface of copper and the white spaces are on a surface of chromium or nickel. The printing elements are recessed by chemically or electrochemically removing the upper layer of metal (chromium or nickel) on these parts or by creating an impression on the surface of the copper and later building up the white parts of the upper metal (nickel or chromium). The depression is from 0.0015 to 0.004 mm deep, depending on the thickness of the metal on the white elements. The depression of the printing elements increases their resistance to mechanical actions in the process of printing and makes it possible to increase the thickness of the ink layer on the form and correspondingly on the printed copy.
A. L. POPOVA