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Drywall Preparation, Priming and Painting
In my story, Preventing Wall Graphics Failures, I mentioned that new drywall must be primed and painted properly to ensure good adhesion of pressure-sensitive vinyl wall graphics. You wouldn’t think that applying vinyl wall graphics to newly painted drywall should be a problem. Of course, problems can and do happen. Especially when contractors rush to get the job done.
According to Arlon’s Chuck Bules, commercial builders are under a lot of pressure to deliver a building on time and face penalties when they miss deadlines. “Sometimes painters will paint right over newly mudded drywall before it has a chance to dry,” Bules says. “That traps moisture under the paint. If you apply vinyl graphics to a wall that hasn’t dried properly, I can almost guarantee adhesion problems.”
And if you don’t wait for proper drying? Any trapped moisture in the drywall can cause the paint to snap, crackle and pop. Well, sort of. The paint can peel, crack and blister. Moisture is the primary reason that paint does not stick to drywall. And when the paint doesn’t stick, neither do the vinyl wall graphics.
Before priming you should also inspect the drywall for any wall damage, such as nail pops and gouges, and any other imperfections in the coating of the taping compound over the seams, corners and nails. The drywall contractor will need to apply a skim coat over any of these problem areas. In many cases these imperfections will stick out like a sore thumb after the vinyl graphics are applied, especially if a gloss overlaminate is used. (That’s a hint. Matte or satin overlaminates are much more appropriate for wall graphics.)
After the drywall is sanded, wipe it down with a clean damp rag. Failure to clean the walls properly often prevents the primer from properly adhering to and sealing the drywall. And debris trapped in the paint will prevent you from achieving a good, smooth surface, which is essential for good vinyl adhesion.
“Painting over a dusty wall can prevent the primer from bonding well to the wall surface,” says Bules. “The best way to wipe down a wall is to dampen a lint-free rag with a mixture of 50% Isopropyl Alcohol and 50% water. Adding alcohol to the mixture speeds up the drying time.” After wiping down the walls, they are usually dry enough to paint after an hour.
New drywall must be primed before painting. Note that I underlined the word “must”. There are no exceptions to this rule. Primers are essential for good paint adhesion – especially if you are painting with a latex paint.
Primers and sealers are not the same thing. Primers are designed so that the paint anchors to substrate. Sealers, on the other hand, form a barrier to prevent something from penetrating the surface. OK, maybe that’s a picky point. But when picking a primer for drywall, make sure that you pick the right one.
Both the primer and the paint must be compatible. The general rule of thumb is that you can use either a latex or an oil-based primer with a latex paint; but you must use an oil-based primer with an oil-based paint.
Under no circumstances can you use a latex primer with an oil-based paint. The reason is that the latex primer will allow moisture to pass from the drywall. The oil-based paint will not allow the moisture to pass. The trapped moisture under the paint will cause blistering and peeling.
The reason that latex primers and paints breathe is that the molecules are much larger with wider spaces between the molecules. The wider spacing gives water vapor a passage way to slip through.
Does that mean that latex primers and paints are a better choice for drywall? Not necessarily so. Because oil/alkyd primers penetrate the surface of the drywall better than latex primers, they anchor better to the surface of the wall. Oil/alkyd primers also form a moisture barrier, which helps prevent moisture from getting behind the applied vinyl, degrading the adhesive and causing the graphics to peel. One downside of using oil/alkyd primers is that they take longer to dry, so you will have to wait longer between priming and painting.
Latex paints and primers have their advantages too. If you are concerned about the environment, the water-based primers and paints have low Volatile Organic Compounds. Bules says that VOCs in oil based contribute 9% to the air pollution that forms smog.
Bules, who has tested many different primers and paints, recommends using Prep & Prime® Gripper® water-based primer sealer #3210 from ICI paints. What he likes about this primer is that it’s good to go, right out of the can and bonds well to “tough to stick to surfaces”. You don’t need thin the primer or add anything to it. In fact, Bules says that you will void the warranty if you modify it in any way. The ICI primer is also good for either indoor or outdoor work. In addition to its use on drywall, you can also use it to prime wood and masonry walls.
For applied graphics, you want the wall surface as smooth as possible. For this reason, you should apply the paint using a short nap foam roller. Bules says that the ICI primer gets good coverage with a single pass. After painting, he recommends waiting 72 hours for the primer to dry, before painting. Drying times, of course, can vary depending on ambient heat and humidity. To speed up the process, you can direct high volume fans over the surface and turn up the thermostat to 80º F (27º C).
After the wall is primed, carefully inspect it again for nicks, gouges or any other imperfections in the drywall job. Many times these flaws are easier to spot after priming. Lightly circle the defects with a pencil and have your contractor float a coat of drywall mud to hide the defects. Don’t worry the drywall compound will stick to paint and primer. Also check for paint artifacts that may have dried in the paint. Using a six inch drywall knife, scrape off any “wall boogers” from the surface.
After priming, the walls are ready for painting. Oracal’s Craig Campbell recommends priming the wallboard with a high quality, oil-based primer such as Kilz® or Zinsser®. “After the primer is dry, apply two coats of a satin or semi-gloss paint,” Campbell says. To reduce any stippling effect in the paint finish, he suggests using a paint roller with a 3/8” nap.
“Avoid using any paint that’s heavily tinted,” says Campbell. “The surfactants and colorants that make up darker paint colors tend to need longer periods to leach or outgas.”
Light-colored flat finish paint is commonly used to decorate drywall surfaces, because it helps hide any imperfections in the drywall job. Painted with glossy paints, these imperfections stick out like the proverbial sore thumb.
While matte finishes do a great cover-up job, you’re just asking for trouble if you apply vinyl graphics to these surfaces. Flat finish paints utilize additives that give the paint its matte or satin finishes. The problem is that these additives prevent good vinyl adhesion. Often the result is a vinyl graphics meltdown: Graphics that are peeling or falling off the wall surface.
Allow adequate drying time between the application of primer and the coats of paint. Tim Boxeth, Marketing Manager for 3M, says that the paint will continue to outgas until it is completely cured. How long will that take? That depends on a number of factors, such as the type of paint used as well as the ambient temperature and humidity. To play it safe, Boxeth recommends waiting at least five days. If you apply wall graphics to an outgassing paint, don’t be surprised if bubbles form underneath the vinyl.
Regardless of what brand and type of paint you’re using, make sure the paint is thoroughly cured before applying the vinyl graphics. “Read and Heed” the paint manufacturer’s recommendations regarding curing times. As a rule of thumb, allow the paint to cure for a week before applying any pressure-sensitive films. High humidity or cold temperatures can slow this curing process down, in which case, you’ll need to allow for additional curing time.
Boxeth suggests using paint from the same manufacturer as the primer, that way you can be sure that both components are matched for compatibility. “All of the components must work together to achieve a good bond of between the paint, the primer and the wall surface,” Boxeth says. “Equally important is that the primer and paint are well cured prior to application of the graphics. This is critical in ensuring that the vinyl adheres sufficiently to the wall. Proper curing is also important when it comes time to remove the graphics. Applying graphics to uncured paint can result in film tearing up the wallboard in the removal process.” Although 3M doesn’t endorse any one paint company, he says that their customers have had good success with Pittsburgh Paints and Sherwin Williams Paints.
Arlon’s Bules notes that vinyl wall graphics do not adhere well to many latex paints. “We tested several drywall paints,” says Bules, “and prefer Sherwin Williams 600-6241 and ICI LM 9116. These two paints hold vinyl very well and these give us over 3 pounds of peel.”
In selecting a paint for drywall, Boxeth recommends a semi-gloss or gloss latex or solvent-based paint. In most cases, adhesion to and removability from these paints is excellent. Still, you should take the time to “Test, Don’t Guess” and conduct a film adhesion test. Apply a piece of the vinyl to be used onto an inconspicuous place on the wall and see whether or not the graphics stay put. If the test sample is lifting at the edges, installer beware!
“Low luster, matte and satin latex finishes can be a problem,” Boxeth says. “Matting agents in the paints often inhibit the adhesion of the graphics to the wall surface. Graffiti-resistant paints are also problematic. Additives, such as silicone, that prevent graffiti from adhering, also prevent a film from adhering.”
If you have any questions about wall graphics applications, call your RTape distributor or contact RTape directly at www.rtape.com.
Labels: painting techniques, vinyl application, vinyl sign techniques, wall graphics