This colourless liquid is the oxime derivative of methyl ethyl ketone. MEKO, as it is called in the paint industry, is used to suppress "skinning" of paints: the formation of a skin on paint before it is used. MEKO functions by binding the drying agents, metal salts that catalyze the oxidative crosslinking of drying oils. Once the paint is applied to a surface, MEKO evaporates, thereby allowing the drying process to proceed. Other antiskinning agents have been used, including phenol-based antioxidants, but these tend to yellow the paint.