Pigment Blue 15:4, Blue 4558 Under the designation P.B.15:4 show largely the same coloristic and fastness properties as P.B.15:3 types, but often exhibit much better rheology. Improved stability to flocculation and other rub-out phenomena make P.B.15:4 an attractive choice, Commercially Available Pigments 447 especially for oven drying paints. The pigments have also gained importance in gravure printing inks, particularly in toluene-based publication gravure printing inks and in various types of flexographic printing inks. They now dominate in these areas. Often, P.B.15:4 types are optimized for use in specific media, such as publication gravure printing inks. In these media the pigment exhibits high tinctorial strength and good flow.