Modern and contemporary artworks made of plastics and exhibited under non-museum conditions in public buildings or in sculpture gardens suffer from weathering. Conservation treatments commonly used for indoor objects indoors, are insufficient outdoors. Maintenance programmes provide a basis, but protective layers on plastics surfaces are needed for long term preservation. The phenomenon of self-cleaning surfaces, as represented in nature by lotus flower leaves, forms the basis for current protective agents. The hydrophobic and dirt-repelling properties of specific nanoscale structures protect plastic surfaces against weathering. This paper describes the degradation of Glass Reinforced Polyester (GRP) resins in outdoor sculptures and the use of protective layers to better preserve plastics. New techniques such as oxygen and or air plasma Plasma Enhanced Chemical Vapour Deposition (PECVD) techniques used to modify the surface of polymers, while enabling hydrophilic and hydrophobic coatings, will be questioned for their use on plastics.