Choosing the Right Primer

August 20, 2020 5 min read

A 5 gallon pail of primer being poured into a paint tray with a paint roller and paint brush.

All new surfaces and most of the repaired surfaces require priming before the topcoat is applied. A primer's main functions are to limit absorption of paint into the surface (seal) and to provide good adhesion (bond). 

What are some of the functions that a primer performs?

  • Provide uniform porosity resulting in a smooth, even topcoat for consistent appearance.
  • Provide a uniform texture or gives "tooth" for adhesion of subsequent coats.
  • Seal chalky surfaces.
  • Seal porous surfaces like weathered wood or masonry, sheet rock or plaster.
  • Seal off knots and sap streaks in wood.
  • Tolerate moist surfaces.
  • Inhibit rusting of iron and steel.
  • Allow adhesion to non-porous substrates (e.g. hard, glossy surfaces such as aluminum, copper or plastic). 
  • Act as a barrier coat for topcoats (e.g. oil/alkyd over galvanized steel or epoxies over alkyds).
  • Act as a barrier coat for substrates (e.g. alkali resistant or tannin blocking).
  • Perform other stain blocking (i.e. cover fire damage, water spotting, or other bleed-through problems).
  • Contribute to hiding. 
  • Provide additional mildew resistance. 
  • Provide a vapor barrier. 

    Is there one single primer that will work in all applications?

    Not really, that's why there are so many primers on the market. Many manufacturers do offer a "universal" primer/sealer/stain-killer with broad performance capabilities. However, the performance properties may not always satisfy the task at hand. To help with choosing the appropriate primer, certain factors must be considered. 


    SELECTING PRIMERS

    Listed below are some factors to consider when selecting the most appropriate primer.

    • What is the substrate? (Use the appropriate primer for the given substrate: wood, steel, aluminum, brick, etc...)
    • Drying time (How soon before re-coating? How quickly must the area be put back into service?)
    • Porosity of the surface (Nonporous surfaces need an adhesion promoting or bonding primer.)
    • Ease of sanding (Will the primer be sanded prior to re-coating?)
    • Ability to prevent the bleeding of stains through the topcoat. (Is stain sealing required?)
    • What will the topcoat be? (Strong solvent topcoats, like epoxies, require primers that resist hot solvent attack.)

     

    Below are types of surfaces and their recommended primer applications:

    Repaint: Primer is usually not needed unless paint is very chalky, bare wood is exposed, or if repairs have been made to the surface with spackle, wood filler, putty, etc.

    New Wood: Prime with quality acrylic latex or oil primer; use stain-resistant primer for cedar, redwood, mahogany or other "staining woods"; oil-based primers are better for severely staining woods.

    Weathered Wood: Thoroughly sand weathered or exposed wood; dust off the surface; then apply a quality latex or oil primer before applying paint.

    Masonry: Prime with a masonry sealer on new or unpainted masonry.

    Ferrous Metal: Prime with a rust-inhibitive high-quality acrylic or oil-based primer. Note: While most rust inhibitive primers are alkyd/oil-based, some latex products have been formulated with rust inhibitive properties. If using a latex primer, check the label to make sure it’s recommended for ferrous metal.

    Aluminum Galvanized Metal: Prime with a high-quality acrylic primer. Note: Galvanized metal is coated with zinc, which is incompatible with alkyd/oil products. 

    Hard to coat/Non-porous surfaces: Prime with a high-quality acrylic bonding primer. Bonding primers offer unparalleled adhesion to some of the most challenging substrates such as: Glazed brick/block, PVC, most plastics, Formica, glass/fiberglass.  These types of substrates propose a challenge due to being mostly non-porous and having almost no surface profile and should be properly deglossed.

     

    Product recommendations based on your unpainted surface:

    Aluminum: 

    Brick (Unglazed):

    Ceramic Tile/Glazed Block: 

    Concrete Block/Rough or Pitted Masonry:

    Concrete Floor:

    Cured Concrete/Fiber Cement Board/ Pre-Cast Concrete:

    Drywall:

    Fiberglass/Glass:

    Ferrous Metal (Iron/Steel):

    Formica:

    Galvanized Metal:

    Hardboard Siding:

    Non-Ferrous Metal:

    Cured Plaster:

    PVC/Plastic:

    Sheet Panelling/Wall Board:

    Stucco:

    Vinyl Siding:

    Vinyl Shutters/Trim:

    Under Wallcoverings:

    Sealing Wallpaper Adhesive:

    • Zinsser Gardz

    Product recommendations for new wood surfaces: 

    Cedar/Redwood:

    Plywood/Pine/Fir/Ash:

    Knots in Wood:

    Oak:

    Cherry/Maple:

    Mahogany/Teak:

    Engineered Wood:

    Product Recommendations for Common Stains:

    Water Stains:

    Tannin Bleed:

    Smoke Damage/Nicotine:

    Ink/Crayons/Graffiti:

    Odor/Pet Odor:

    Grease Spots:


    In conclusion, please remember that the purposes of priming include sealing the substrate from stain bleed-through, providing a uniform surface for topcoat, and to help assure a tight bond between the paint and the surface to be painted. Proper surface preparation and applying the correct primer is necessary to ensure a proper paint foundation prior applying the topcoat. If you have any questions, please call your local Regal Paint Centers store. 



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