The oxidative drying of alkyd paints has many similarities with the way lipids are oxidized in biological systems. Metal salts based on Co, Fe and Mn are added to accelerate the oxidative drying of conventional alkyd paints. Although the mechanism by which alkyd paints dry has been the subject of numerous investigations, little information is available on the structure and the actual mechanism by which driers catalyze the oxidation process. In this communication we describe the identification of metal clusters in drier solutions by electrospray ionization mass spectrometry (ESI-MS). Evidence is provided for the presence of several metal clusters ranging from M3 up to M6 as well as the coexistence of mixtures of (mixed-valence) clusters in the same solution.