The invention relates to the use of an organic cerium sol in paints, in particular finishes or varnishes, to improve durability. More particularly, the sol used can be a sol comprising an amphiphilic acid system, an organic phase and particles in the form of agglomerates of crystallites with a d80, advantageously d90, of at most 5 nanometres, 90% (by weight) of agglomerates comprising 1 to 5, preferably 1 to 3 crystallites. The paints incorporating a cerium sol have improved water resistance properties and mechanical properties.