Primer (paint) - When Primers Are Used

When Primers Are Used

Primer is a paint product that allows finishing paint to adhere much better than if it were used alone. For this purpose, primer is designed to adhere to surfaces and to form a binding layer that is better prepared to receive the paint. Because primers do not need to be engineered to have durable, finished surfaces, they can instead be engineered to have improved filling and binding properties with the material underneath. Sometimes, this is achieved with specific chemistry, as in the case of aluminum primer, but more often, this is achieved through controlling the primer's physical properties such as porosity, tackiness, and hygroscopy.

In practice, primer is often used when painting many kinds of porous materials, such as concrete and especially wood (see detailed description below). Priming is mandatory if the material is not water resistant and will be exposed to the elements. Priming gypsum board (drywall) is also standard practice with new construction because it seals the wall and aids in preventing mold. Primers can also be used for dirty surfaces that, for some reason, cannot be cleaned, or before painting light colors over existing dark colors.

Primers can usually be tinted to a close match with the color of the finishing paint. If the finishing paint is a deep color, tinting the primer can reduce the number of layers of finishing paint that are necessary for good uniformity across the painted surface.