William C. Feist thinks he knows why. The homeowners decide to upgrade and put on a good latex paint. But that last coat of a new type of paint can be sufficient to cause catastrophic failure, often right down to bare wood. When people in the paint industry have a problem they often consult with the chemical company that supplies them with the ingredients they put in their cans. On a blustery day last winter, the institute's technical director, Walter J. Gozdan, led the way through this maze, happy to talk about the intricacies of what people in the paint industry like to call coatings.
Oil paint forms a tough plastic film as the binder reacts with oxygen in the air.
The binder can be a natural oil, such as linseed squeezed out of flaxseed, or oil modified with alkyds. Latex paint forms a flexible film as water evaporates and the once-floating spheres of binder and pigment move closer together and fuse. Latex paint was inverted at the end of World War II using synthetic rubber as the binder. Today the binder is most often a pure acrylic, a vinyl-acrylic or a vinyl acetate. The critical difference between oil and latex paints is that they do not cure in the same way.