Do I Need to Use Paint Primer?
Paint colors, dyes and compositions are getting better all the time. Effects that would have been unthinkable just a generation ago are becoming easier than ever to achieve, from special matte finishes that resemble suede to effortless crackle glazes that make faux effects a cinch. One thing paint cannot do terribly well on its own, however, is bond to every possible surface without a little help. This is where paint primer comes in. If you have come online in search of vetted and reliable info on which primer to use and when, the following survey may be of some use.
The basic rule of thumb for paint primer is that it is necessary whenever you cannot create a totally flat surface for painting. Surfaces with cracks, holes or depressions that aren’t properly sealed could greatly reduce the paint’s ability to set effectively, so inherently porous substrates such as wood, drywall and concrete tend to come with primer recommendations attached. The natural holes in such materials can create an uneven surface for painting. But each of these materials requires somewhat different care, and it pays to understand what distinguishes one from the next.
Wood is the most common surface for paint primers, a fact that is hardly surprising considering its organic nature. The reason you always want to prime wood before painting is twofold – to protect the paint, and to protect the wood. A number of modern paints dry into proper color and hardness via evaporation, meaning they require the water to find its way into the atmosphere. The problem is that wood is a notoriously thirsty substance, and it is easy for water to get absorbed into the grain itself. Often the paint will begin to pucker and peel if the wood isn’t dry, making it necessary to scrape and start over. Paint primer creates a watertight seals between the two and ensures the paint has a smooth and adhesive surface with which to bond.
A second reason you always want to prime a wood surface is because the same absorption can quickly undo your attempts at an even coat. Lighter paint colors especially will often reveal the telltale whorls of wood grain even after several passes, requiring you to paint over and over for a truly solid hue. Although you could indeed take the hours necessary to paint repeatedly, often you can achieve the same effect with a few fast coats of primer first. The advantage extends well beyond mere convenience – primer tends to cost far less than paint, easing your financial burden in the process.
The wood itself can be injured without a primer in place. Although a negligible amount of water is absorbed during drying, considerably greater amounts may leech into the grain if that painted surface is exposed to the elements. Without a primer in place, it’s not unusual for repeated thunderstorms to take their toll, creating devastating conditions for mold, mildew and warping. Although many people consider outdoor paints to be waterproof, often they are anything but – their hardy nature derives from their ability to absorb rainwater with ease.
Of course, paint primer is recommended for a variety of other materials as well. In concrete and drywall, for instance, you simply want to seal the surface and create a solid bond without having to worry about similar problems with drying and moisture. For metals – especially those prone to rust – a paint primer can protect the surface itself and keep moisture locked out. Plastics too can benefit from a coat of paint primer, particularly if they are porous in nature or you are putting a light color over a darker one. Finally you may need primer to marry two different paint types together, as when you apply latex over oil paint.
One thing primers are decidedly not for is hiding blemishes or “sealing in” mold and mildew. If you are working with a material that may have absorbed or produced an organic population such as this, it is essential to clean thoroughly before you paint. Dry everything for several hours and wait to see if the problem recurs. It is better to discard a rotted plank than to use primer to delay the inevitable!