Papermaking technology and the growth of mineral pigment use in printing and writing papers, from a precipitated calcium carbonate (PCC) producer's perspective. Heavier bleaching to achieve higher brightnes causes opacity to fall, a physical reality dictated by the principles of the Kubelka-Munk equations. Reduced light absorption by the bleached fibers equates to higher brightness but, this mjeans light passes through the paper more easily, so opacity is lower. Excellent light scattering makes PCC a cost effective means of simultaneously improving both brightness and opacity.