Finally, Paint Coatings for Each Job
The right type of coating is vital. If you pick the wrong paint, it won't matter how much effort and money you spend on your job. Too many flawlessly great paint jobs deteriorate quickly because poor quality primer and paint were used.
A dependable rule of thumb is to complement the existing coating. If you're painting or staining on top of latex paint, recoat with latex. You might have all sorts of choices if the material is uncoated, nevertheless, you still need to consider weather, maintenance, and durability to determine the best covering for the job.
No-Fuss Painting Using Primers
Primer is the unsung hero of any quality paint job. It determines how well the finish is protected and exactly how long the paint can last. Knowing when to use primers screws up painters about as much as which primers to use. Basically, you will need to use a primer when you are coating a new or bare surface; changing colors, textures, or finishes; or making a surface more uniform. About the sole time you don't have to prime is if you are recoating with the same paint and finish over a sound paint, for example, a flat latex paint over another flat latex paint.
To make sure of compatibility, choose something that's part of your paint system. By paint system I mean a primer and top coating manufactured by the same company. The labels of better paints always recommend specific primers and top coats for various materials and conditions. If you don't want to cope with reading the fine print, ask to view the spec, or data sheet, on a specific primer. In case a spec sheet isn't available, ask to see what's known as a “specifier’s guide,” although these guides probably have significantly more information than you will ever need and you might need help translating a few of the terms and specifications.
Primers form an even base for the top coatings by penetrating, sealing, and bonding to all or any types of bare surfaces. Without first priming a new or reconditioned surface, you will discover that the top coatings end up flaking off much sooner than you would expect. Even though you can use additives such as Emulsabond, don't make the mistake of thinking that primers are optional, or can be made out of diluted paint.
Usually in one coat most primers smooth out surfaces and places which may have been scraped and sanded. Sometimes a surface will require a second coating of primer to ensure an even undercoat, but often one is enough. The house pictured below is an example of a project where two coatings of primer were used. The bare wood siding was primed with an oil-based primer for extra adhesion. Then, a latex primer was applied over all the siding to give it a smooth base for the top layers. Some climates almost demand another coat of primer. I've heard about one contractor in Florida who always double primes to ensure that his work last. If you live near salt water, I would recommend that you take into account doing the same.
Primers highlight surface conditions by pointing out imperfections such as loose fibers in drywall and raised wood grain in trim. You might feel that a primer would even out a surface, but if you run your hand over a primed portion of wood trim it always feels rough. That's because primer causes out loose grain as it penetrates. After a dried primer has been lightly sanded, the smoothed surface is ready for coats. (Here's a tip: In the event that you tint your primer the color of the top coat, you can actually quicken the painting process by lowering the amount of top layers needed. Tinting is mainly used for color changes, although it is also handy for areas like bare drywall.)
Solution for Priming Interior Surfaces and Ceilings
I recommend using latex primers wherever possible. Ask your paint dealer for advice on the best primer for interior trouble spots, such as the laundry room and bath, that require a good sealant and a water-resistant primer. I've always used alkyd primers in wetter areas of the home, although there are great latex primers that seal about as well. I prime most drywall interiors with latex, especially the sleeping rooms, living room, and closets. I usually spray a latex primer on new construction because new structures have satisfactory vapor barriers. Also, I could paint an oil-based top coating over latex primer.
Older houses demand room-by-room decisions on what primer to make use of. If the home doesn't have a vapor barrier or good ventilation, you will require a primer that seals the wall surfaces and keeps water from getting between the surface and the paint.
Latex stain blockers and sealers can be the response to priming wet rooms inside your home. These quick drying primers help condition areas with water, cigarette smoke, and tannin spots, plus they can be recoated rapidly, sometimes within the hour. Pittsburgh's Seal Grip is a superb latex stain blocker with few VOCs and all the features of an oil-based stain blocker. Quick drying alkyd primers such as Kilz have pigmented shellac (with high VOCs) that also functions as a stain killer and sealer, but I don't recommend these for latex top coats, the shellac might show through the latex. In case your latex has what's known as “good hold" or hiding properties, it will maintain an even sheen over primer. You are able to assure compatibility by using a high quality latex stain blocker such as Seal Grip.
With regards to walls, remember that plaster and drywall are different. Plaster is highly alkaline, in particular when it's new, and it can leach alkaline salts if it isn't properly sealed. There are plenty of primers you can use on plaster, depending on its condition and on the top coat and finish that you've planned.
Drywall is much less alkaline than plaster. I prime drywall with a latex primer, unless the top coatings will be an oil-based paint, in which case I'll use an alkyd primer. (I know that there are perfectly good latex primers for any type of top coat, but old patterns are hard to let go of.) When painting new drywall, I will sometimes add joint compound to the primer for just a little texture. Mixed with primer, joint compound also helps level over any sanding markings or roughness.
Method For Priming Interior Wood
When selecting primer, you should consider the type and condition of the surface, the sort of paint (alkyd, latex, or epoxy) that is planned for the finish coats, and the kind of finish (flat, semi-gloss, or glossy).
Most often I prime interior wood trim with an exterior alkyd primer, which seals new wood and replaces lost wetness in older wood. There's also good water-based enamel primers for interior wood. Special conditions, such as the high moisture common in bathing rooms and kitchens, may call for a breathable latex primer if you can't prime all around the wood. If you can completely prime the wood before it goes up, an alkyd primer will protect most of the trim from water. Assess conditions like these carefully and seek the advice of a professional if your job has many different variables
Primers For the Exterior
Even though I favor latex paint for the exterior, I still would prefer to use alkyd primers on exterior wood. They simply do a much better job of priming bare wood. I'll use an alkyd primer if I know that the home does not have any major internal vapor problems and that the wood is in good condition (which usually means that it is new), especially if I had access to the siding and trim before it is attached to the building. It's always best to seal all around the wood (but not the ends) to provide each piece its own vapor barrier.
New redwood and cedar siding, as well as hardboard siding, needs special attention. Redwood and cedar will bleed tannins for a long time, even if the timber has air-dried for a few months. Before priming, you should wash out the tannin with a light detergent, and follow this with a good rinsing. Redwood and cedar are rather porous, so you may need to hold back a day or two to let them dry out. There's a good chance that more tannin resin will seep to the surface, so avoid priming with latex because the resin will bleed through. Instead, use two coats of any alkyd primer/sealer, and use high quality latex for the top coatings. Any staining that occurs after that can usually be washed off with special timber cleaners.
Hardboard siding, new or already coated, presents a special challenge. The lack of grain or anything resembling a porous surface makes hardboards such as Masonite difficult to bond to. If the wood is new then pressure wash and rinse it. If water still beads up, wash it again to remove all the wax. Seal new hardboard with a specially developed hardboard primer/sealer, such as Pittsburgh Paints Permanizer Plus Wood Stabilizer. When blended with a top coat, Emulsabond makes a great hardboard primer. These and other high quality sealers also work well on metal or vinyl siding, plywood veneers, textured wood, and other composite sidings.
Amazing Primers For Metals
Every metallic should be cleaned of oil, grease, rust, or any other residue before you prime it, so the primer gets thorough contact with the area. Most metal areas can be cleaned with a good thinner. Galvanized metals sometimes come from the factory with a stabilizer that can be tough to eliminate, and may need more than just thinner. Consult with your paint store if you would like to be certain a primer will work on new galvanized metallic surfaces.
You can find primers for each and every type of metal. Ferrous metals, manufactured from iron and steel, should be primed with a rust inhibitor. Rust is almost impossible to completely remove unless you sandblast it, and even then small pockets of rust can stay that will grow back again under an unsealed surface or the wrong primer. Rust inhibitors totally seal the outer layer from contact with air. Some companies make reference to these primers as direct-to-rust or direct-to-metal (DTM) primers. Smaller projects like handrails can be primed with aerosol rust inhibitors such as Pratt & Lambert's Effecto Spray Enamel, which I've experienced success using.
Other metals, including copper, aluminum, bronze, and brass, should be coated with zinc-chromate primer. Some paint companies have a specific primer for new galvanized metal. Older galvanized metal can be primed with a rust inhibitor like those mentioned above.
Much like any layer, the more time the primer has to flow and contact the surface, the better the adhesion. Quick setting primers don't flow much whatsoever and stay right where they're applied, for good or for bad. A clean surface is particularly important when you use an instant drying primer. Note that some paint manufacturers recommend cleaning metals (and most other surfaces) with a thinner, while others recommend against using any type of solvent cleaner. Scan the directions carefully.
A vintage technique that still is effective for cleaning new or old metals is washing the outer layer with a one-to-one mix of vinegar and water. Vinegar is an all-purpose, inexpensive cleaner that will also etch a steel material if mixed at that ratio. Etching metal works like sanding wood. It provides surface "teeth" for better adhesion. That same ratio is convenient for new rain gutters or uncoated aluminum siding. However, it should not be utilized to completely clean galvanized metals, because the vinegar will harm the galvanizing.
Method For Priming Masonry
Whether it's inside or out, masonry usually requires a primer or sealer that will resist water and alkalis. Alkalis are salts that leach out over time, leaving a chalky stain called efflorescence. The cause of the efflorescence, usually moisture, must be resolved for alkali-resistant primers and sealers to help. New masonry has to cure for 90 days before you prime and paint it, especially if it is highly alkaline, like stucco.
Sherwin Williams has a masonry primer called Loxon that withstands alkalinity up to pH 13; it could be painted on masonry that is a week old. Stucco, which is actually coloured mortar and filled with lime, is an excellent surface for Loxon, as is new plaster or poured concrete. Pittsburgh Paints also offers a primer for new, high-alkaline masonry, called Speedhide Alkali Resistant Primer; it's provided for oil-based paint. You also can add this primer to cured masonry with a latex top coat, but it's important that you use latex only on low alkaline masonry. In these situations I've had good luck adding Emulsabond to the latex for extra adhesion. I recommend it for nearly all masonry applications.
Etching with muriatic acid used to be the only way to speed up the curing time of concrete. You could still etch if you are so willing, although if I never see another box of muriatic acid, that would be just fine. (If it etches concrete, imagine how well it etches epidermis!) Etching requires a bucket, hose, brush, gloves, and complete eye and skin protection, don't forget a respirator, especially when you mix the acid with the water. Important: Add the acid to water, not the other way around. If you add drinking water to acid it'll splash and burn off anything it contacts. And blend it in the correct ratio, usually one to three. Make sure you have brushes, sponges, towels, and least one 5 gallon bucket of clean water for emergencies, and another 5 gallon bucket for rinsing.
Reconditioning older, peeling cement floors can be a chore. It's best to keep them well managed and recoat them regularly, before they need to be completely redone. Concrete flooring in really sad condition should be sandblasted, or you may use a new system called Peel-Away that makes prepping masonry a bit easier (it's still no picnic). If the surface is in good condition, prep the floor and remove any trace of grease or wax with a good thinner.
For new concrete floors, I would recommend a concrete stain manufactured by H&C or Okon; they come in water based and silicone acrylic. My preference is the water based stain, since silicone is a wax that eventually will wash off. Concrete stain penetrates and seals without needing scraping or sandblasting, and resists fading better than a top covering like latex.
Older, pre-painted cement floors need to be repainted with a similar top coat, whether latex or alkyd. A latex top coating is best applied over a typical concrete sealer, but Emulsabond also is effective. An oil-based top layer requires an oil-based enamel or epoxy concrete conditioner. I'd add Penetrol to the primer for an extended lasting bond.
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