Everything to Know About Paint Primer

Updated November 9, 2021
Interior of modern kitchen with blue walls
Pixel-Shot – stock.adobe.com

If you're looking for professional quality results without nasty surprises from your paint job, then you need the skinny on paint primer

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There’s nothing like a fresh coat of paint to revive a tired interior or to make your home’s exterior pop. But sometimes, the results are far different (and far less majestic) than you’d hoped. In some cases, a coat of primer could have provided the showroom results you imagined. But what, exactly, is paint primer, and when do you need it?

What Is Paint Primer?

Primer and paint are alike in a lot of ways: you apply both with brushes and rollers, they have roughly equivalent drying times, and they come in latex and oil-based varieties.

But each function is very different. Basically, where paint is the style, primer is the substance.

Primer contains resins, which allow it to penetrate porous surfaces such as wood or drywall. This helps to create a surface bond that enables paint pigments to adhere longer, more durably, and more uniformly. 

The result is a finish with fewer paint bubbles and cracks and is more resistant to chipping, peeling, and fading. 

An undercoat of primer helps seal the paint against water damage from without and chemical seepage from within, so it resists bleed-through from previous paint colors, oils from wood surfaces, or rust from metal walls. 

Primer and paint make a perfect team because each compensates for the other’s shortcomings. Primer, for example, is less durable than paint and does not hold up well in direct sunlight or harsh weather conditions unless you use a primer specifically manufactured for outdoor use.

On the other hand, paint does not do well on slick or oil-coated surfaces and will quickly begin to show signs of fading and damage unless it has an undercoat of primer to help the pigments stick. When used together, though, primer and paint can lead to professional-quality finishes, whether you’re painting interior walls or your outdoor patio furniture.

When to Use Primer

Determining if you need primer will depend on many factors, including the kind of surface and conditions, such as high heat and humidity, that your paint will face.

Prime Surfaces for Primer

Because of its porosity, you should use primer for wood surfaces. If you're painting new wood, you can use either latex or oil-based primer. Wood with stains or high tannin content like redwood or cedar requires a stain-blocking primer, though, to prevent bleed-through and to ensure you get a uniform finish. 

Drywall needs a latex primer because oil-based products will create an uneven surface by affecting both old and new drywall grain, resulting in an imperfect finish once you apply the paint. 

Rusty metal surfaces need a corrosion-resistant primer, whereas shiny materials like glass or tile need bonding primers.

In addition, if you’re painting a surface with a lot of staining, then primer can help give you the uniform finish you want. And, best of all, there are even primers that can block odors. So, if you’re painting a room with a heavy smell of cigarette smoke, animals, or other unsavory atoms, specialty primers can help take care of the funk.

High-Traffic, High-Heat, and High-Humidity Areas

In addition to identifying the surfaces—from wood to drywall to metal—that work best with primer, you also need to look out for environmental conditions that can be tough on your paint. Areas where your finish faces a lot of wear and tear or high heat and humidity will probably need primer. That would include kitchens and bathrooms, as well as an exterior paint job. 

Really, though, if you want your finish to look brand new for years to come, then you can’t go wrong with primer, no matter where it goes.

How to Use Paint Primer

Man cleaning kitchen walls with a cloth
Syda Productions – stock.adobe.com

The first step to any paint job is to clean the surface thoroughly. Prepping and cleaning your kitchen walls before painting, for example, will likely involve degreasing the surface and sanding out any blemishes.

For wood, this can also mean stripping off any excess oil and sanding down any large knots. For metal, this means scouring off any rust. And for drywall, make sure to sink screwheads just below the paper so they don't create "pops" in the finished product.

Prepping Your Primer

If you're covering dark or very bright colors, you may be able to use spot-priming for areas that have some oil bleed-through or have stains, as opposed to priming the entire area, particularly if someone primed the surface before the previous paint job.

To prep your primer to cover stains or bleed-through, you’ll want to tint your primer slightly to the color of your paint. You can accomplish this by adding a small amount of paint to the primer and mixing thoroughly. Tinting can help improve the overall finish of an interior painting job, especially if your final color is very dark or quite bright.

A Word About 2-in-1 Primers

You may have heard about 2-in-1 paint-and-primer solutions that claim to have the benefits of both. These products have received mixed reviews—in part because you cannot mix paint and primer in the same can. Chemically, it’s just not feasible.

Instead, manufacturers create high-quality, super-thick paint that acts as primer and paint, so long as you use two coats of paint. One coat of a 2-in-1 product may work for a previously painted wall, but will not be enough for a fresh surface. Expect to pay double the cost of normal paint, up to $50 for a one-gallon can.

DIY vs. Professional

The costs of a new primer and paint job can vary widely, depending on the size of the project and the type and condition of the surface. In general, hiring a professional painter will cost $20 to $50 an hour.

On the other hand, if you DIY your paint job, you will only need to cover the cost of the tools, primer, and pain. Typically, a gallon of primer and paint will cover around 400 square feet. Primers typically cost $10 to $30 per gallon, while a gallon of paint ranges from $20 to $100 per gallon.

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