Prime Considerations

Selecting the Right Primer

 

If you’ve decided to tackle a painting project and you go to your local paint store, you may be surprised to learn how many different primers are available. A primer is used under a finish coat to provide adhesion to the substrate and seal any stains that may come through the finish coat. This is a crucial step in the painting process. 

           


Photo: Courtesy of Sherwin Williams

If you are painting pressure-treated bare wood outside, your best bet is an exterior acrylic primer. Since these are water-based, they dry quickly and clean up easily with soap and water. Most often used on hand rails and deck bands, this type of wood is the most difficult to keep paint on because it is smooth and impregnated with chemical preservatives. If the wood is not kiln dried after the chemical treatment, you should not paint for at least six months.

Acrylic primer is recommended for siding products. Some siding (LP “Smart Side,” for example) are already factory-primed, which allows you to paint directly without a dedicated primer.   

Cedar requires a product that will block the tannins from coming through the finish paint and a good slow drying oil is best for this. Cedar is used primarily because of the high tannin content, which allows the wood to last longer than most others. The tannins are oils in the wood that will eventually seep through most acrylics leaving a stain. Most wood siding on the Outer Banks is cedar, either shakes or lap siding and is subject to this leaching. The tannin blocking oil products generally take up to 48 hours to dry and clean up with mineral spirits.  

If you have rusty screws or nails, you will need a rust-inhibiting primer. All rust scale should be removed before priming. The idea is to build up a high mil thickness to block the stain from coming through. Once the  nail begins to rust inside the wood, the rust will continue to leach out and, unfortunately, become a matter of routine annual maintenance...as any painting contractor on the OBX will tell you.

Interior primers are used for everything from new drywall to wood trim to hiding water stains. For new smooth drywall, latex “surfacing primers” are best. These products are thick and meant to be sanded before the final coats are applied. The application amounts to a skim coat of drywall and is very effective in hiding seams, which are frequently noticeably after the drywall has been finished.

On textured drywall surfaces, inexpensive latex primers can be used as an alternative to the pricier flat latex finishes. There is no need for a thicker surfacing product. These primers are also good for drywall repair areas. If your finish is eggshell, satin, or semi-gloss, primer is essential to ensure that a flat spot is not evident when the areas is touched up or repainted.

If you have experienced a water leak, an interior stain blocking oil product will be required. These products typically dry fast and may require multiple coats to completely block the stain effectively.

           

If you intend to paint wood paneling, cabinets, or trim, you will need to use an oil primer that both blocks stains and sticks to glossy surfaces. The surface should be lightly sanded with 220-grit sandpaper before priming to ensure that the primer has a good bite. Most often, primers for glossy surfaces dry quickly and clean up with mineral spirits or alcohol.

 

Whatever your situation, your local paint dealer should have a recommended system of primer and finish to fit the need. Depending on your finish colors, your paint store may even recommend tinting the primer to allow for better coverage on your finish coat. Make sure to describe the project completely and remember to select a good grade of product for maximum longevity.

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