Printing Studies With Black Inks.

The correlation between rheological and printing properties was studied for a systematic series of black inks. The inks consisted of four different carbon black pigments at four loadings in two vehicles. Measurements included viscometer and Inkometer readings; transfer to a coated paper during the letterpress printing of solids; and the uniformity, blackness, and gloss of the prints on the coated and on an uncoated paper. The level of rheological values, the level of transfer and of print quality properties, and the correlations among them depended on the nature of the ink ingredients. The type of paper also affected the correlations. It was concluded that rheological measurements can be used for comparing the relative printing properties of a series of inks only if the inks contain the same ingredients. The agreement of film splitting theories with printing results confirmed the importance of the low shear viscometric nature of inks.