Ti[O.sub.2] is the most important contributor to the optical properties on white prints. It is responsible for opacity, whiteness and also strongly influences gloss.

When light falls on a pigmented ink film, four processes can occur simultaneously.

* reflection, refraction - at the film surface; and

* scattering, absorption - within the film.

As discussed before, absorption in the case of Ti[O.sub.2] is the least important and can be neglected. Figure 3 illustrates the main processes occurring when a beam of light falls on a white print.

If the surface of the print is smooth, some of the light (A) will be reflected specularly and contribute predominantly to gloss. However, much of the light (C) will penetrate the film and be scattered by Ti[O.sub.2] particles in all directions.