What Is Paint Primer? Everything You Need to Know

Paint primer can be a critical step before applying a color coat. This neutral base coat is formulated differently than paint, and it helps prep the surface so that paint can adhere better and last longer. While it's more work to use a primer than to skip it, paint professionals recommend that you brush, roll, or spray one or two coats of paint primer to produce a better color coat. There are instances where you can skip it, specifically, if your wall is totally smooth or if you use a paint with primer built in, but, in most homes, that is not the case.

Priming is as much work as laying down the color coat. Every stroke of the brush and every roll of the roller is the same as you would do for the eventual color coat, and you want to make sure it's perfectly smooth so your eventual color coat will also look similarly smooth.

Here's what you need to know to make sure you roll on an effective primer coat and get your painting job off on the right foot.

How to Paint Wood Like a Pro

Reasons to Prime Before Painting

Paint primer is designed to provide a stable surface that subsequent paint layers can lock onto. Paint primer also helps to hide surface stains.

Primer Provides a Stable Base Surface

A surface's porosity is the condition that most often warrants the use of a paint primer. When the surface is too porous, too much of the paint will draw into the surface. Multiple coats of paint are required before the paint can develop a thick, protective shell.

The opposite can be a problem, as well. When the surface is too glossy, color coat adhesion is difficult because the paint cannot lock onto the surface. Paint primer, being slightly rough and porous, provides an excellent texture for the paint to grab onto.

Primer Covers Stains

Paint primer is also valuable for covering up lower stains. With the stains covered, the color coat is free to do its job of providing beautiful colors instead of covering up stains.

Also, because primer is typically less expensive than paint, it makes economic sense to use primer for base coats rather than paint.

You can never go wrong with priming. If you have little confidence about the condition of the wall prior to painting, the default choice is to prime it.

When to Use Paint Primer

Not all conditions need to be present for you to decide to prime the surface first. You may want to use paint primer if you encounter any of the below situations during your painting project.

If the Surface Is Porous

A highly porous surface usually means that primer is needed. Newly installed drywall is highly porous in two ways: the bare facing paper on drywall and the dried joint compound covering the seams. Bare wood is even more porous and always requires a primer. Masonry such as retaining wall blocks and bricks need paint primer.

If the Drywall Is Skim-Coated

A skim coat is a thin swipe of drywall compound laid over bare drywall. Considered a level five finish, the highest grade possible, a skim coat is not something you encounter often. But as with bare wood or drywall paper, it is highly porous and thus requires at least one coat of primer before painting.

If the Previous Coat Is Glossy

Glossy base coats do not hold paint well. A light scuffing with sandpaper and a coat or two of primer will help the color coat stick. Even if you decide not to scuff that glossy sheen, using a primer will help subsequent coats stick. Plastics and glossy paints nearly always require some type of roughening of texture prior to painting.

If You Are Changing the Color From Dark to Light

Avoid the problems that come with repeatedly laying down expensive light-colored paint over darker colors. Instead, first treat the surface with two layers of white primer if the existing color is extremely dark.

When going from a light color to a dark color, note that most paint retailers have the ability to tint your primer. This brings the color of the primer closer to that of the wall finish color, reducing the number of primer coats and color coats you lay down.

If the Surface Is Stained

Spotted or stained surfaces benefit from a coat or two of priming before painting. Consider using thicker primers such as Kilz 2 or Kilz Max for these conditions.

Which Type of Primer to Use

Depending on your surface, there are different types of primers that will work best for your project. There are three main types of primers: oil, latex, and shellac.

Oil-based Primers

Oil-based primers work well a variety of paints, including both latex and oil, and are typically the most popular primer choice. Because these primers provide a thicker coverage, typically oil-based primers will stop any stains on the wall from showing through. Note that they are slow-drying and can release VOCs.

Shellac Primers

When you have a serious primer job involving stains, smoke, smells, and other issues, a shellac primer could be the way to go. This will provide the most coverage, however, it also releases the most fumes.

Latex-based Primers

A latex-based primer is the friendliest of the primers since it comes in low- or no-VOC options, and they're generally easy to clean out of your paint brushes and other supplies. You can use latex-based primer on drywall, as well as wood, brick, and other materials. However, it's important to note that they aren't as efficient at covering up stains as other primers.

How Much Primer You Need

This helpful calculator acts as a guide for how much primer to buy in advance of starting your project.

When You May Not Need Paint Primer

While priming is usually the best bet, you can often get by without priming under any of the following conditions.

If the Walls Are Very Clean

If your walls are perfectly clean and in good condition, you might be able to eliminate the need for primer. One way to clean walls before painting is to create a thin mixture of tri-sodium phosphate (TSP) and water and wipe down the walls with a soft cloth. If you choose not to use TSP, attach a clean brush attachment to the end of a shop vacuum and clean off major debris like cobwebs and dust.

If You Are Painting From One Color to a Similar Color

One need for primer is to readjust the base color for your new color to brilliantly and accurately show up. If previous and new colors are the same, or even if they are similar, the need for primer is reduced though not entirely eliminated.

Using Self-Priming Paints

Self-priming paint is essentially a paint that is thicker than regular paint. Because it is thicker, it builds up higher and forms a thicker coat. It is preferable to use a separate primer and paint. But if the walls are basically in good condition, you can use a combination paint and primer.

Self-priming paint is not the miracle cure that many homeowners believe it is. Laying down a thicker paint build makes for a weaker coat that takes longer to dry. Additionally, the higher per-unit cost, and the possible need for more than the advertised single coat, means that it may not end up being a money or time saver.