Why should wood surfaces be sanded before painting?

Sanding wood surfaces before painting is primarily done to allow for smoother application and better adhesion. When wood is sanded, it not only smooths out the surface but also creates a slightly rough texture. This roughened texture provides more surface area for the paint to grip onto, which significantly enhances adhesion. Good adhesion is critical in ensuring that the paint bonds well to the surface, thus preventing peeling or chipping down the line.

Additionally, sanding helps remove any existing imperfections, such as old paint, dirt, or potential contaminants, which can interfere with how well the new paint adheres. It also allows the paint to go on more evenly, contributing to a more uniform finish. Overall, proper sanding prior to painting is an essential preparation step that contributes to the longevity and durability of the paint job.