First, the typical paper-coating mineral particle is micron-sized. This is well below visual resolution, so larger base stock features can be filled in and visual uniformity improved.
Second, the minerals in coatings are rigid and packed with pore space distributed among the particles. Pores create bulk and scatter light. More bulk means more coating volume, and more smoothness and surface uniformity at the same coat weight. Good light scattering is essential because most inks scatter very little light back to the observer; they simply absorb certain wavelengths. The pores in the coating, created by narrow-distribution pigments like Specialty Minerals Inc. (SMI) precipitated calcium carbonate (PCC), take the wavelength-depleted light that forms the image and scatter it back to the observer. More scattering means more image intensity.
Third, coatings provide important subjective qualities. Most observers equate gloss, brightness, and whiteness with quality. People also tend to connect the quality of the paper with the quality of the information on the paper. Advertising is thus more effective when the graphics exhibit accurate and intense color, high gloss, and uniform optical density.
Fourth, coatings provide a base for ink. The coating pores remove solvent, yet reject the body of the ink: it remains on the surface, where it is most efficient at absorbing light.
By enhancing coating performance, SMI PCC products improve overall print performance. That’s why the right minerals choice matters so much.
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