An Investigation Into the Emulsification of Lithographic Ink and Water.

Rapid and accurate determination of water content of offset ink is not feasible by wet analytical methods. The use of IR analysis is attractive since it is rapid and requires very small samples. However, this method becomes unreliable unless the water is actually emulsified into the ink. Suspended larger droplets of water lead to variations in the required determinations of the ratio of absorbance of water hydroxyl groups to absorbance of the reference carbonyl groups. Calibration of the system with ink samples containing known amounts of water is essential. This calibration assumes that off press preparation of samples is equivalent to water in ink emulsion formation on an offset press. Results indicate that such off press emulsification is not possible unless very efficient blending techniques are used. The method is very practical when the ink pigments are relatively transparent. Opaque pigments require attenuation of the signal with resultant loss of accuracy. Study of variables such as mixing methods, choice of OH bands for calculations, choice of cell materials, and methods of cleaning cells were made. The variations of ink tack values as a means of determining degree of emulsification was also studied.