Near the protection of the building materials from weather and providing a decorative finish the remaining of the aesthetic appearance during use is equally required by the end-users.

The contamination of architectural exterior coatings with dirt resulting in graying should be avoided, as it can negate any other positive property which an exterior paint may still have.

The tendency of a coating to attract dirt on the surface is affected both on the complex dirt composition, on dirt particle size and on the chemical nature depending on rural or urban air pollution and on the paint formulation know-how using ingredients to optimize surface hardness, hydro-phobicity, surface texture and photo-activity.