Whether priming is necessary, or not, is a common consideration before beginning a painting project. There are many different types of primers available and even ‘paint and primer in one’ so it can sometimes be confusing to know what’s best for your painting project.

Before being able to determine if a primer is needed, it’s important to understand what a primer is and what type of primer you may need for your project.

A variety of primers serve different purposes and are to be in different situations.

What is a primer?

A primer is a coating, that is applied before painting. A primer may have a similar appearance to paint, but the product formulation is different. Using the correct primer is essential for a quality finish and performance

What is a primer used for?

Primers have a variety different purposes. The three primary purposes are: adhesion, stain blocking, and improved surface preparation.

Adhesion:

Many primers are designed to promote excellent adhesion to a variety of surfaces. These primers may be referred to as a bonding primer. While paint alone may properly bond to a variety of substrates, a primer can improve performance of the paint system. In some situations, a primer is an absolute requirement.

Metals, existing oil based finishes, some plastics, and glossy surfaces are all substrates that can benefit from a primer.

In addition to promoting a strong bond with metals, primers often provide a protective layer on metals to slow down oxidation and rust. It is common for many metal product to come pre primed or prefinished from the factory. An example of this would be a steel door. When purchased, these doors already have a protective prime coat applied.

Galvanized metals and aluminum can be a challenging surface to paint. Galvanized metals contain zinc as a sacrificial protective layer. There are many primers formulated for metals and availability of different product may vary by region. Check with your local paint store to discuss your project and get the appropriate products available in your area.

Existing oil based finishes, commonly found on interior trim/woodwork should be primed, prior to painting with a water based (acrylic/latex) paint. An oil based primer or premium waterborne bonding primer, such as Stix, often work well in these situations. I often find paint failures in homes where a low quality latex paint has been applied over existing oil based polyurethane finishes. Without proper adhesion, the paint easily chips and flakes away from the surface.

Latex paint has chipped off of the stiles on this interior door. The paint was applied directly over the existing oil based varnish.

Blocking:

Stain blocking primers are used to create a barrier between the substrate and the new paint. Blocking primers prevent “bleed through” appearing in the new finish. Water stains, smoke stains, drastic paint color changes, and some raw wood all benefit from a blocking primer to “hide” what you are painting over.

Some woods, such as pine, cedar, and oak are prone to tannin bleeding through the surface. This brown or yellow staining can occur immediately after painting or years down the road. Shellac or oil primers commonly provide the best resistance to tannin bleeding, however, in some situations the tannins may still come to the surface.

There are some water based primers that are showing promising results on our cabinet painting projects. We have successfully painted over and dyed woods with no indications of tannins leaching through the surface. These products are intended for the professional market, but it shows that waterborne products are advancing. I anticipate water based products to all but replace the need for solvent based products in the near future.

Smoke and nicotine stains are a problematic surface to paint over. If you simply paint over smoke damage or cigarette staining, it’s likely that the staining will bleed though the surface before the paint is dry. This is especially common on light color paints, such as a white ceiling. An appropriate stain blocking primer is essential before apply paint.

Many of these stains are problematic because they are water soluble. As the wet primer (or paint) touches the tannins or contamination, the stains will dissolve and migrate through the wet coating. Stain blocking primers are effective in locking in the stain and sealing it within the primer. Stubborn stains may require multiple coats of primer to fully seal the surface.

Drastic color changes can also benefit from a prime coat. Some painter prefer to have the primer tinted to gray or a color that matches the new paint color. Some colors are harder to cover than others. If you have ever tried to change a wall color from red to white, you already know how challenging it can be.

The knot on this pine trim has appeared through the painted surface as a result of tannin bleeding.

Surface Preparation

What does surface preparation mean? It can mean different things in different situations. In generic terms, it is using a primer to improve the appearance of the painted surface.

Porous surfaces, such as wood, masonry, and drywall will suck moisture out of the paint causing premature drying of the paint. Paints “dry” or “harden” by undergoing both a chemical reaction as well as water/solvents evaporating from the surface. Porous surfaces may accelerate moisture being drawn out of the paint before chemical curing has completed. This can result in flashing, decreased adhesion, or degraded performance of the paint.

New drywall installation and drywall wall repairs completed with joint compound should be primed before painting. Drywall and traditional joint compound (spackle) are both very porous and will commonly cause flashing in the surface. The flashing occurs from the paper drywall surface and compound absorbing moisture at different rates. Since the drying of the paint is impacted, the paint will have a uneven final appearance. Drywall and repairs should be primed before painting to seal the surface.

Some primers are designed to improve the substrate to be painted and a improved finish. These undercoating primers will fill in minor scratches and blemishes to provide a glass smooth surface to paint. Characteristically, these primers can be sanded easily to provide a uniform smooth surface. Using a quality primer and sanding smooth will provide the highest quality finish on interior millworks, cabinetry, and furniture.

Flashing visible on drywall not properly primed before paint application.

Conclusion:

Primer is a vital component in many paint systems and will improve performance on virtually any paint. While there are many scenarios where a primer is not necessary, there is almost no downside to using a primer on most painting projects.

Choosing the correct primer is essential. Professional painters have years of experience and training to aide their decision on what, if any, primer should be used. If you are new to the painting trades or a DIYer, be sure to research the appropriate paint and primer for a successful project.

Availability of paint products vary from region to region. This is a result of distribution networks as well as state VOC laws. For this reason, it is hard for me to provide specific product recommendations to the masses. Readers of this post may not have access to the products that I use personally.

Painting is a systematic process. Priming is just one step within the process. Cleaning, repairing, sanding, and top coat application are also critical steps for the best results. A quality paint job can only be achieved with the proper preparation and not taking short cuts.

Failing to properly prepare and paint a surface can create disastrous results. Fixing these problems often take considerable time and money to resolve. I often find coating failures when visiting clients homes for estimates. These failure require us to take two steps backwards before we can proceed with our work. This is wasted time and money.

If you have questions about your painting project, drop them in the comments below and I will do my best to help.

NEPA Remodeling offers cabinet painting and interior painting throughout the Scranton PA area. To schedule a consultation for a painting project in your home, you can easily fill out a request for a phone or in home consultation.

Do You Have To Prime Before Painting?