Choose the Right Primer for Your Next Painting Project
Get the lowdown on the four most common formulations, and an overview of specialty primers for every possible substrate and situation, so you can find the right product for the job.
Synopsis: For this article, senior editor Patrick McCombe consulted experts from Sherwin-Williams, Dow Coating Materials, and Benjamin Moore, as well as FHB’s most-trusted painters. The result is a comprehensive look at a product that is never seen in finish work but is crucial for the longevity of that finish work. McCombe discusses the four main formulations of primer—oil-based, water-based, shellac-based, and synthetic shellac-based—as well as a product that hit the market relatively recently: paint and primer in one. He also provides helpful information on “do it all primers” and 11 specialty formulations: rusty-metal primer, vapor-barrier primer, problem-drywall primer, gray-tinted primer, PVA primer, high-bond primer, mold-killing primer, concrete-and-masonry primer, low-VOC primer, peel-bonding primer, and drywall primer.
Primer is one of those everyday building materials I’ve never given a lot of thought to. I’ve always used latex primer because it dries fast and is easy to clean up, but a quest for a durable exterior paint job on some basement bulkhead doors convinced me that I needed to know a lot more about the primer I use. So in the interest of science and a longer-lasting paint job, I interviewed primer experts from Benjamin Moore, Dow Coating Materials, and Sherwin-Williams. I also talked to Fine Homebuilding’s most-trusted painters about what they use and why. I’m grateful for everybody’s help, and I was surprised by the consistency of their advice. Here’s what I learned.
Primers have a specific job
Primer and paint have different jobs, and they’re made differently for that reason. Primer prepares a surface for a topcoat and improves the topcoat’s adhesion. Paint sticks to the primer and provides color, dirt resistance, and weather resistance. As part of its job, a primer may have to cover or seal in stains, level an uneven surface, or effectively stick to smooth or glossy surfaces. This wide range of needs is what gave birth to all of the specialty primers you can now find on store shelves.
Unlike a topcoat, primer isn’t made for long-term exposure. It doesn’t have the same resistance as paint to UV rays, mold, weather, pollution, and job-site wear and tear, so you shouldn’t leave it exposed for any longer than necessary, especially outdoors. Generally speaking, more expensive primers cover better and hold up better than less expensive primers because they have higher-quality resins as well as additives such as mildewcide, according to Benjamin Moore field integration manager Mike Mundwiller.
Because primers aren’t supposed to be exposed to the weather for a long time, any primer that’s been outside for more than a few weeks should be lightly sanded, thoroughly cleaned, and reprimed. Some primers have a sweet spot for when they’re best topcoated. This is spelled out—along with the expected coverage, the recommended application thickness, and the final film thickness—in the individual primer’s product data sheet or technical data sheet. You can find this information at a paint store and on paint manufacturers’ websites. Product data sheets are also the best sources for minimum and maximum application temperatures and other application instructions.
Primer can be applied with a brush, a roller, or a sprayer. What tool to use depends on the size of the job. For small jobs, a brush is best because it’s fast to deploy and easy to clean. Rollers are for medium-size jobs, and sprayers are for large jobs. When spraying, my experts suggest going over the sprayed primer right away with a brush or roller to ensure that there are no tiny bare spots.
From Fine Homebuilding #280
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