Surface Properties of Thin Printing Ink Layers.

Following an outline of the factors in printing which are influenced by the surface characteristics of the ink, the nature of the surface phase in printing inks and the concept of critical surface tension are discussed theoretically and the use of measurements of spreading, contact angle and tilting angle in the study of surface layer behavior is considered. A report is given on investigations into the surface properties of thin printed layers of four different combinations of apolar and polar ink pigments and vehicles. Tables are given showing (1) equilibrium contact angle and work of adhesion of water on printing ink films of different thickness; (2) equilibrium contact angle of water on printing ink films of different thickness on zinc and copper; (3) effect of additives on water wettability of ink films; and (4) rolling-off constant of water on ink films. Graphs show equilibrium contact angle versus surface tension. Results are discussed.