The exterior painted surfaces of automobiles, various other types of vehicles, airplanes, bridges, buildings and the like, undergo quality changes (deterioration) with the passage of time as a consequence of exposure to water, ultraviolet radiation, ozone, and so forth. In response to this, numerous surface-protective agents have been proposed for the purpose of protecting these painted surfaces. For example, the use of polydimethylsiloxane-containing wax compositions as surface-protective agents for automobiles (car wax) in quite familiar. However, while these car waxes exhibit an excellent initial water repellency, this water repellency is lost with time, i.e., their water-repellency retention is poor. Silicone resin-blended wax compositions have also been proposed. While these compositions have a better water-repellency retention than polydimethylsiloxane-containing wax compositions, it can still not be said that their performance in this regard is entirely satisfactory. In order to eliminate the effect of ultraviolet radiation, which is one cause of the deterioration under consideration, it has also been proposed that the wax composition additionally contain an additive such as an ultraviolet absorber. Unfortunately, these additives are in all cases low-molecular-weight organic compounds, and they are readily eluted or washed out within a short period of time under the influence of rain. The retention or maintenance of their effect is thus again poor. An additional problem is that commercial car waxes, typically being pastes or solids, require the expenditure of substantial effort for their application to the painted surfaces. Thus, not only does waxing require a wiping-off step, but waxing must be done frequently in order to retain the water repellency. These work inputs to be borne by the car owner are by no means trivial.