2. Pigments and colorants

2.1 General features

Pigments and dyes are among the most important constituents of ink, as they give it its optical characteristics. They carry the message, create the decor, add color and gloss, etc. By definition, a pigment is a colored substance, generally of crystalline structure, insoluble in the ink vehicle and dispersed at a very high level of subdivision. Colored pigments are chosen from a wide variety of products of mineral or organic origin. Most of the pigments used in printing inks today are synthetic organic pigments. Pigments are selected according to their properties and price, which can represent up to 65% of the ink's "material" price.

Their color comes from the presence of chromophore groups on their molecules (typically: