As paint formulators face the challenges of a tougher regulatory environment, aggressive competition and greater customer demands, they must reach deeper into their tool boxes to deliver solutions. Innovative raw materials and creative processes can help the paint chemist address these issues. One type of specialty additive on which chemists have begun to rely is the class of products known as microspheres. Although solid microspheres are widely used in reflective traffic paint, the focus of this article will be on the unique properties of hollow microspheres. Hollow microspheres are a small, but growing, element in many a formulator's arsenal. As the name implies, microspheres are small, spherical particles. Particle sizes range from 12 to 300 microns in diameter, and wall thickness can vary from several microns to as low as 0.1 micron. They can be composed of acrylonitrile, glass, ceramic or phenolic materials. Because they are hollow, the true density of microspheres is lower than that of other non-soluble additives.