Lead in paint made it extremely durable. However, by the 1970s, people realized that lead in paint was a serious health hazard, especially for children. The FDA banned the use of lead in all residential and commercial paints in 1978. Since then, paint manufacturers have formulated latex paints that are safer to use, and better for the environment.
Latex Paint Features
Latex paint does not actually contain latex, and high-quality exterior house paint is fortified with 100 percent acrylic or urethane binders. It is flexible and breathable, compared to oil-based paint. This means that it's less likely to crack when exterior surfaces shift, expand and contract as the weather changes. Because latex paint is breathable, it also allows some moisture to pass through without blistering or peeling. Additionally, the pigments in water-based paint are more stable than those in oil-based paint, and less likely to fade.
When Oil-Based Paint is a Better Choice
If you have an older home with multiple layers of old oil-based paint, repainting it with oil-based paint may be a wise idea. Latex paint shrinks as it dries, and this can stress poorly adhering underlying layers of paint, causing it to crack and peel prematurely. If your old paint is chalking, water-based paint won't adhere to it. Chalking is normal oxidation; if you run your hand over the siding on the sunny side of your home and it comes away white, that's chalk. Chalky siding has to be thoroughly scrubbed and power washed if you have any chance of latex paint sticking. Your other choices are to prime the entire surface with oil-based primer, followed by two coats of latex paint, or repaint the siding with oil-based paint. Since barns were originally painted with oil-based paint, many formulations of barn paint are also oil-based.
Painting Metal Surfaces
Metal and steel siding, wrought iron railings and metal gutters can be painted with either oil-based or latex paint. Oil-based paint tends to adhere better, and if the surface is smooth and somewhat rigid, like metal, you have less chance of it peeling. Oil-based paint is also thicker, and you may be able to paint fewer coats of it on intricate or hard-to-paint surfaces.
No contest: water-based paint is much easier to use. It dries to the touch within an hour and can be recoated the same day. It cleans up with soap and water instead of solvents, and is very low odor. It is safer and cleaner to manufacture, store and use. Oil-based paint dries slowly, allowing bugs and dust to settle on the surface while it's still wet. You generally have to wait until the next day to apply a second coat. It has a strong odor, is flammable, and still contains some fairly toxic chemicals.