Influence of crystal size of Yellow 13-type pigments on optical and rheological properties of lithographic inks

Abstract

Use of a modern diffractometer and detailed knowledge of the crystal lattice structure have improved ability to size crystals of CI Pigment Yellow 13-type pigments. This has enabled confirmation and refinement of correlations observed in earlier work between crystal sizes and optical and rheological properties of commercially available pigments in lithographic inks. The correlations indicate that the dispersion procedures used have produced inks in which the pigments exist substantially as individually dispersed crystals. The correlations also indicate that the crystals of the commercially available pigments are effectively perfect. An alternative explanation on the basis that the various pigments have similar degrees of aggregation and imperfection of crystals is also possible, but improbable due to the widely different compositions and sources of the pigments. Whether or not abietyl resin added to improve dispersibility of pigment remains on the crystal surfaces in inks has not been resolved.