When to Use a Primer or Sealer

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While it is always wise to use a primer or sealer to achieve the highest quality paint job, it is especially important in the following circumstances:

• when painting new wood or another surface that has never been painted before

• when painting chalky surfaces severely weathered paint

• when repainting a surface that is uneven or badly deteriorated (Note: Weathered wood should be thoroughly sanded before painting)

• when painting a surface that has been stripped or is worn down to the original surface material

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Types of Primers and Sealers

As with paints, there are two broad classifications of primers and sealers: latex or water-based products; and oil-based or alkyd products.  Virtually all paints will adhere well to either type.  However, some oil based paints can tend to crack prematurely if applied to a latex-based primer, so be sure to follow the manufacturer’s directions.

Latex primers and sealers – especially those with acrylic binder – perform at least as well as oil-based products in all but two instances:  The first instance involves severely staining wood, where oil-based primers provide the best performance; the second situation involves heavily chalked surfaces, where oil-based primers offer better adhesion.  If you decide to use an oil-based primer on any wood surface, be certain that the wood is very dry before applying the primer.

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Exterior Primers

The necessity of using a primer or sealer – and the type of product to use – varies from job to job.  Here are some general guidelines for common applications.

• New Wood.  Use either a quality acrylic latex or an oil-based primer.  Oil-based stain-resistant primers are the best type to use on severely staining boards.

• Previously Painted Wood.  If bare wood is exposed, sand thoroughly, dust off, and apply a quality acrylic latex primer; if the old paint is very chalky, and all the chalk cannot be removed, use an oil-based primer.  Otherwise, if the old paint is still adhering well, a primer may not be needed. 

• Weathered Wood.  Use either a quality latex or oil-based primer.  Apply immediately after surface preparation (thorough sanding and scraping).

• Stucco, Concrete and Other Masonry.  On new masonry, or older surfaces that are porous, apply a latex masonry sealer.  Consider using a “block filler” if the surface is very rough, as with cinder block.  These heavily pigmented products expand upon drying to fill the pores and provide a smooth, uniform finish.  In a repaint situation, use sealer only where the old paint has been removed during surface preparation or through weathering.

• Ferrous Metals.  To help prevent rust, apply two coats of a corrosion-resistant primer (acrylic latex or oil-based) when painting any metal that contains iron.

 

Primer on Primers

Surface	Recommendation
NEW WOOD	Prime with a quality acrylic latex or oil-based primer.  Use stain-resistant primer for staining woods; oil-based primers are better for severely staining woods
REPAINT	Primer usually not needed unless paint is very chalky or bare wood is exposed.
WEATHERED WOOD	Thoroughly sand weathered or exposed wood, removing all loose fibers; dust.  Apply a wood primer before painting.
MASONRY	Apply a latex masonry sealer if surface is fresh or very porous.  In a repaint situation, use sealer only if old paint is removed by scraping or wire-brushing.
FERROUS METAL	Apply two coats of acrylic latex or oil-based corrosion resistant primer before top coating.
ALUMINIUM, GALVANIZED IRON	Clean the surface.  Remove any powdery oxide with coarse steel wool.  Primer not necessary with 100% acrylic latex topcoat, unless galvanized surface shows rust.

• Aluminum or Galvanized Iron.  When using a 100% acrylic latex paint, no primer is needed when painting aluminum or galvanized steel, as long as there are no signs of rust or oxidation; however, a primer should be applied if you plan to use an oil-based or vinyl water-based paint.  When rust or oxidation is present, use an acrylic latex or oil-based corrosion-resistant primer after removing the rust or oxidation.

 

Choose a quality California Paints primer for your home’s exterior

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Interior Primers

Most interior primers are designed for very specific applications.  Often, they serve a practical purpose by warding off potential problems that might arise due to the nature of the surface being painted, or the environment in the room.  Other times, they serve an aesthetic purpose; namely, enhancing the appearance of an interior paint job.  And they always enhance the adhesion of the top coat of paint to the surface below.  So, it is wise to use primers to achieve the best interior painting results.

Many interior primers come in both latex and oil based formulations, so you often have a choice of products to use.  Keep in mind, however, that latex products are much lower in odor, which is a significant advantage on indoor projects.

Here are some of the most common types of interior primers and the situations in which you should use them:

• Stain-blocking Primers.  These interior primers protect the new coat of paint against “bleed through” of staining matter like dirt, grease, rust, smoke residue and waterborne material by sealing off the stain-producing agents.

• Drywall Primers.  While they are called primers, these coatings actually serve as sealers over drywall and joint compound to give the top coat of paint a uniform appearance.  Despite the name, you can generally use them on new plaster as well… but first, check the directions on the label.

• Vapor Barrier Primers.  These primers are useful in bathrooms, kitchens, laundries and other damp rooms, where they help minimize the passage of moisture out through the walls.  By doing so, they reduce the chance that exterior paint will fail, or that wall insulation will become saturated and lose its effectiveness.  They also help maintain a comfortable level of indoor humidity during colder months.

• Latex Enamel Undercoaters.  Using these primers under semigloss or gloss paint helps ensure that the top coat of paint will form its maximum gloss and have a uniform look.  For best appearance, you should lightly sand the primer to remove brush marks and/or any fibers that may come from the surface being coated.

• Bonding Primers.  These specialty primers are designed for use on very slick or glossy surfaces such as glass, tile, Formica®, or vinyl-coated paneling (but not countertops).  Their purpose is to help form a secure primer-top coat paint system.

 

Choose a quality California Paints primer for your home’s interior

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