For New Alkyd Paints, Oil and Water Do Mix
March 26, 2012
Regular alkyd paints (also known as oil-based or solvent-borne paints) form a hard, glossy surface that is easy to clean and resists scratching, water, and chemicals. Used primarily for trim, doors, cabinets, furniture, floors, commercial walls, and other high-use areas, they are popular with professional painters because they adhere well to most surfaces and “level out” to hide brush marks and small surface irregularities, curing to a smooth surface that latex paints cannot match. Unfortunately, standard alkyds typically contain flammable, potentially toxic petroleum-based solvents that emit high levels of volatile organic compounds (VOCs). They require ventilation during application and petroleum distillates for cleanup, and excess paint has to be disposed of as hazardous waste.
Waterborne alkyds from Benjamin Moore, Sherwin-Williams, and others offer the performance of traditional alkyds with almost no solvents and far fewer VOCs. Water is the solvent for both latex paints and waterborne alkyds, but these two paint types cure very differently. “Latex” paints contain very small acrylic or vinyl acetate particles that coalesce when the water evaporates to form a flexible film that is semi-permeable to vapor. The film dries and can be recoated in a couple of hours but may remain somewhat soft and vulnerable to damage until fully cured, which can take almost a month. Alkyds, on the other hand, use polyester resins that react with oxygen and cure to a hard, vapor-impermeable coating. Alkyds require about 24 hours before they can be sanded and recoated—at which point they are already hard—and then continue to cure throughout their lifespan.