Many people think that primers are useful only when doing exterior painting, but that’s a mistaken notion.

Like exterior primers, interior primers make surfaces more uniform and help paint adhere better, but they can do a lot more, according to Debbie Zimmer, paint and color expert at the Paint Quality Institute.

“Interior primers can actually help prevent a host of problems and enhance the appearance of a finished paint job,” she says. “By choosing the right type of primer for a particular project, it’s even possible to pinpoint the performance benefits you’ll get.”

Here’s a quick sampling of some of the more common types of interior primers and how they can help improve your next paint job:

Stain-blocking primers. Walls and other interior surfaces often have water stains, smoke residue, grease, or other contaminants that can “bleed” right through a new coat of paint to ruin its appearance. To prevent that from happening, Zimmer advises applying a stain-blocking primer before painting to seal off the stain-producing agents. “These primers come in both latex and oil-based formulations, but latex stain blockers have much less odor, which is always a plus when working indoors,” she says.

Vapor barrier primers. These interior primers are typically used in bathrooms, kitchens, and laundry rooms to help prevent moisture from passing through the walls. By doing so, they help keep the wall insulation dry and reduce the chance of an exterior paint failure due to moisture exiting the interior. Vapor barrier primers also help maintain a comfortable level of humidity inside the home during the heating season.

Kitchen and bath primers. These coatings are often used in the same areas as vapor barrier primers, but they serve a different purpose. Specially formulated with biocides and stain blockers, they help control the growth of mildew and mold in rooms that tend to be damp or humid.

Drywall primers. While these coatings are called primers, they really function as sealers, which are close cousins of the primer family. As the name indicates, they are applied over drywall and joint compound to help conceal the differences in their appearance and impart a more uniform look to the completed paint job.

Latex enamel under-coaters. These primers are excellent for use under semi-gloss or gloss paint to ensure that the paint will develop its maximum gloss. After applying a latex enamel under-coater and letting it dry, Zimmer says it’s important to lightly sand off any visible brush marks before applying the glossy paint.

Bonding primers. When painting a slick material like glass, tile, Formica, or vinyl-coated paneling, it is always wise to use a bonding primer. These primers are specially formulated to adhere to slippery surfaces and help create a more secure bond between the primer and paint.

Even if you’re on a very tight budget, you shouldn’t fail to apply a primer when the circumstances call for one: the primer may actually save you money. That’s because you may need fewer coats of paint, especially on a previously unpainted surface. Likewise, if you are applying a dark-colored paint, you can often get away with fewer coats by applying a tinted primer beforehand. The net effect may very well be a more economical paint job.

Source: The Paint Quality Institute