Primer is specially formulated to make sure the top coat of paint adheres to the surface below, whether it’s new or repaired drywall, bare wood, stained surfaces, or even dark paint colors. Using a quality primer creates a more professional-looking finish and also makes your topcoat of paint last longer.
When To Use Primer
New Drywall
Primer is an absolute must on new sheetrock (Drywall and Plasterboard) and mudded (joint compounded) surfaces. The new drywall and sanded mud are extremely porous and will soak up a lot of paint at first, so the primer works to seal the drywall and create a uniform surface. Porous surfaces like drywall mud will cause visible differences in the final sheen of your paint, called “flashing.”
To help achieve a consistent appearance with your final coat, it is always a good idea to first use a primer when painting new drywall or over drywall patches. A quality drywall primer is typically much less expensive per gallon than multiple coats of quality interior latex paint.
Bare Wood
Bare wood is among the more difficult substrates for a paint topcoat to adhere to and soaks up even more paint than drywall does, so you definitely need to prime it. If finish-quality paint is applied directly to bare wood, the wood can absorb the paint’s solvents, drying it prematurely.
Remember, all varieties of bare wood have some sort of color. Without a primer, several layers of paint may be necessary to obscure the wood grain and ensure even, uniform color. Proper primer use also protects wood from warping, mildew and other water damage. Thin layers of paint are water-permeable, and the wood below can still be affected by moisture.
Stained Surfaces & Dark Colors
Primers block stains from water damage, knots in wood, and rusted metal. If you try to paint over these stains without using a special primer, the stains will bleed through the paint even after multiple coats.
As with stains, dark colors can bleed through lighter ones, so using a white primer will create the best base coat for your new color.
Metal
While not all metals require priming, it’s highly recommended if the metal will be exposed to moisture. Oxidation (or rust) begins the very instant water contacts bare metal. To combat oxidation, metal primers often contain anti-corrosion agents, such as zinc. When painting a metal surface that is already showing rust, the best course of action is to thoroughly clean the surface and remove the rust. If that’s not possible, special primers are available that chemically convert rust to solid metal salts, which is a good option. The surface may not be as good as shiny, clean metal, but it’s a lot better to paint than a rusty surface that will eventually just rust through.
Plastic
The most common reason to prime a plastic surface (e.g., plastic or vinyl shutters) is to make a drastic color change. Primers reduce the layers of paint necessary to completely cover previous colors, and will help the paint make a thorough bond with the surface being painted. Some plastic surfaces are especially “slick” and pose a unique challenge for even the best primers when trying to get a coating to stick to them. If you choose the correct bonding primer for your application you will be far more likely to get great adhesion of your finish coat to the surface.
When NOT To Use Primer
If the surface has already been painted, is in good shape, free of patches, without stains, and is a fairly light color, then you can skip the primer and go straight to paint. Thoroughly wipe down the surface first to remove dust and debris, and that should be all the prep work you need to do.
How To Use Primer
All primers are applied using a brush or roller—the same as paint. They can also be used in an airless sprayer. One coat may be sufficient, but for stains and dark colors, you may need two if the paint is bleeding through. After the primer is completely dry, you’re ready for your paint.
Still have questions about primer? Let the painting experts at Zoe’s ProEdge Painting help you out. Ask us your questions in the comments or give us a call today!