Painting is one of the most, if not the most, common ways of finishing wood. While it can be argued that painting hides the natural beauty of wood, which some people would call less attractive, there are many cases in which paint is the best finish to use. The only question is which paint is the best for a particular application?
Take a trip to the paint store or the paint department in your local home improvement center and you can be overwhelmed by the number of choices. Worse than that, all the paint cans look pretty much the same, making it even harder to make a selection. Without some knowledge of the different paint products, it’s hard to decide what paint you need for the project you are doing. But there’s a good reason why there are so many choices; they’re all designed for different applications.
The question then becomes, what is the best paint for the particular project you’re working on. That depends on the material you are painting, the finish “look” you are after, and how much the finish will be subject to potential damage.
Oil Based Versus Water Based
When we start talking about types of paint to use, the most basic question that most people think of is whether to use oil-based or water-based paints. There has been a trend in the paint industry towards water-based paints for several decades now, as the technology improves, making it possible to use new water-based paints for purposes which previously required oil-based ones.
This trend has not been driven by these new products being better than the oil-based products they are intended to replace, except in one area; they are lower VOC (volatile organic compounds). In other words, they are less polluting than oil-based paints. That’s an advantage in this day of high public interest in the environment; but it’s more of an advantage for commercial operations, than it is for the home woodworker.
In exchange for that benefit, the water-based products which are touted as replacements for older oil-based ones really aren’t the same. High gloss water-based paint doesn’t provide as shiny a finish as high gloss oil-based ones do. Water-based paints intended for painting metal surfaces don’t dry as hard as those which are oil-based. Although not a paint per-se, water-based paint thinner doesn’t clean your brushes as well as mineral spirits (an oil-based product) does. It seems we are inevitably giving up something, in order to use these products.
On the flip side of that coin, water-based paints are considerably easier to work with, mostly because the clean-up is much easier. Water-based paints can be cleaned out of our brushes, rollers and sprayers with water, which is both plentiful and cheap, not to mention that it doesn’t cause us any disposal problems. Our water treatment plants are able to deal with paint in our wastewater, so it doesn’t even end up polluting.
We aren’t so fortunate with oil-based paints. Since they are made with an oil base, they don’t mix with water. That means cleaning them up with something that can mix with oil. Before, we used mineral spirits for this, but now, there are water-based paint thinners to use. They don’t work as well, but they aren’t as polluting. Even so, they can’t just be dumped down the drain. Rather, they need to be treated as hazardous waste and either returned to the paint store for disposal (not all paint stores accept thinner for disposal) or taken to a hazardous material disposal site.
One other difference that should be considered, when we’re talking about the difference between oil-based and water-based paints is that oil based paints tend to “flow” better, hiding brush strokes. There are products to help improve this, Floetrol for water-based paints and Penetrol for oil-based paints. Even using these products, oil-based paints will still provide a smoother finish.
Then There’s the Sheen
The next big thing that people are concerned about is the sheen of their paint. Depending on the paint, it can be dull or shiny, or anywhere in-between. This affects how the finished project looks, as flat paint does a better job of hiding imperfections, while high gloss paint does a better job of showing off any details in the wood, such as might be found in fancy architectural molding.
By and large, oil-based paints can provide a higher gloss finish than water-based ones can, although not all oil-based paints are high gloss. In fact, you can get oil-based paints and water-based paints which are equally flat.
Many people have trouble describing the sheen they want, with certain terms being confused on a regular basis. Yet there is a specific order these paint sheens fall in, going from flat to high gloss:
|Sheen||Gloss Level||Measurement Angle|
|Low Sheen or||8-12||60°|
To clarify what that table is saying, the “gloss level” refers to how much light the painted surface reflects. To keep everything even, the paint is applied to a piece of glass for testing. The measurement angle is the angle that the measurement of the light reflection is made at, which is intended to approximate the angle that most people would be looking at it.
An ultra-flat paint, which is likely to be used as a ceiling paint, is measured at an 85° angle because that’s the angle most of us will see it at, if you consider looking straight ahead as 0°. Gloss and high-gloss paints, which might be used for architectural molding around doors and windows, is more likely to be viewed at close to eye level, hence the 20° measurement angle.
Please note that not every company will use all of these identifiers, nor will any one paint line reflect all the various sheens that a paint company offers. Companies develop products which they believe will best meet their customers’ needs for that product line. If something doesn’t make sense for a particular application, then companies won’t bother developing a product, even if you or I have a special need for that particular sheen in some particular paint.
One of the advantages of the glossier paints, from semi-gloss through high-gloss, is that they are less porous. In a home, this means that they are less likely to get stained by dirty hands and grease splatters. At the same time, they are also easier to clean up, when they do get soiled.
What Sheen to Use Where
Based upon that information, we can see some standard applications for paint sheens all around us; things like:
- Ceilings in a home – flat
- Walls in a home – flat or to eggshell paint, depending on personal preference
- Kitchen and bathroom walls – usually semi-gloss for ease of cleaning
- Wood architectural trim – semi-gloss through high-gloss, depending on personal preference
- Exterior of the home – flat
- Painted wood furniture – usually semi-gloss, perhaps high-gloss if children’s furniture
High Quality vs. Low Quality
Another major factor in selecting any paint product is the quality of the product itself. There are many different manufacturers out there who make paint; but they are not all equal; nor are their products. Some companies specialize in producing low-cost paints, while others seek to provide high-quality.
So what’s the difference between low-quality and high-quality paint? It all boils down to the ingredients, specifically the percentage of solids in the paint. Those solids are the pigments (which are normally ground powder in a solvent) and resins. Some inexpensive paints try to increase their solids by adding inert ingredients, like clay; but these paints do not last well. The rest of the paint is liquid and can be considered solvents.
While both paints may appear the same and even be of a similar viscosity, the high-solids paint will leave a thicker, tougher film when it dries. Between the amount of pigment included in the paint and the solids, the paint will do a better job of covering and hiding whatever is beneath it.
It is almost always recommended to use two coats of paint, no matter what you are painting. Even a high-quality paint, which covers extremely well, may have pinholes or thin spots from the application of the paint, which will allow the underlying color or substrate to show through. However, a high-quality paint will often cover in one coat, whereas a low-quality paint will require two or even three coats to cover the same surface.
Primer Makes a Difference
Using the right primer with the paint makes a lot of difference too. Primers perform three basic purposes:
- Sealing pores in the surface, so that the paint doesn’t soak in
- Bonding with the substrate, primers do this better than paint
- Stain coverage
This third purpose, stain coverage, has a lot to do with how well the paint covers underlying stains or coloration. If the underlying substrate has water stains, mold or any other discoloration, using a stain killing primer might be the only possible way of ensuring that the paint you apply won’t be discolored.
These stain killing primers are usually fast-drying materials, such as shellac, with a high amount of white pigmentation. They don’t have high solids content, as they are intended to soak into the surface of the wood, thereby sealing it. This combination of characteristics allows these primers to accomplish all three of the purposes listed above.
While stained and varnished wood doesn’t fall into the same category as wood that is stained in the ways above, it isn’t (even though the same term is used). It is not necessary to apply a stain killing primer in these cases, as the stain is sealed into the wood by the varnish. However, you might still decide to use a stain killing primer, for its ability to cover the color of the stain, especially if you are going to apply a light colored paint over a dark colored stain.
Whenever applying paint over stained and varnished wood, the varnish should be sanded lightly to break up the surface and provide something for the paint to “bite” onto and promote adhesion. If the varnish is high gloss, it’s useful to use a deglosser as well, which will dull the finish of the varnish, promoting adhesion.
Some Specialty Applications to Consider
There are always special applications for paint, which don’t follow the “one coat of primer than two coats of paint” formula. They either need special paint products or special treatment. While it might be possible to paint these surfaces by other means, chances are that the paint finish will not last.
A garage or workshop floor is probably one of the most difficult surfaces to paint. There are two problems to deal with here; oil that has soaked into the floor and the wear that the floor will endure, due to cars and other heavy items rolling or being slid across the surface.
Before painting any garage floor, the floor needs to be thoroughly cleaned and degreased. You may not be able to get the stain all the way out of the concrete, but you want oil and grease out, so that you don’t end up with adhesion problems. Even oil-based paints will have problems sticking to oil spots on the floor.
The best possible paint to use for this application is an epoxy paint. This is a two-part material; essentially an epoxy adhesive with a low viscosity. Pigmentation and even contrasting color chips may be added to the epoxy paint to cover the coloration of the floor. The high tensile strength and bonding strength of the epoxy helps to ensure a long life. It is also very hard for a paint product, providing good wear resistance.
You’ve probably never noticed, but the ceilings of most homes are not finished quite as well as the walls are. It’s just plain harder to hang and finish sheetrock on a ceiling, than it is on walls. This creates more irregularities in the finish, which are covered by using popcorn texture to cover it up.
You want to use the flattest paint you can get for painting any ceiling, so as to hide these irregularities. At the same time, ceilings are almost always painted a bright white, so as to reflect as much light as possible. Even indoors, we are accustomed to the idea of light coming from above.
But a brilliant white paint does something else for us too; it helps provide the visual impression that the ceiling is higher up. If any darker color is used, the ceiling height will appear to be less; and if the color is dark, you might find yourself ducking, feeling like that ceiling is coming down on you.
Most walls are relatively smooth and flat, before they are textured. That texturing helps to hide any imperfections in the taping and finishing process, as well as any dents or nail holes that you or your family make in the wall.
But what if you move into an older home and the walls aren’t quite so good? In that case, the first thing you need to do is decide whether you need to refinish the walls altogether, perhaps even removing existing drywall and replacing it.
If you don’t want to go through that much trouble, a lot can be done by repairing holes, applying new texture or even just painting. A flat paint, much like you would use on a ceiling, will go a long way towards hiding those imperfections, whereas a semi-gloss paint will make them stand out, because of the light reflecting off the wall unevenly.
Metals can be difficult, especially since some of them don’t provide good adhesion for paint products. But regardless of the type of metal you are painting, there are things you can do, which will help to ensure a good, long lasting finish.
To start with, make sure that you have removed all oxidation, especially of steel. Clean the metal to remove oils and greases as well. If you make anything out of metal, the metal you purchase to make it invariably has oil on it from the mill that made the metal. Then use a primer which is appropriate for that particular metal. This is especially important for difficult to paint metals, like aluminum. Paint does not bond well with aluminum, if an aluminum primer is not used.
Warning: aluminum primer is extremely messy to work with and hard to clean up.
While there are a number of water-based paints on the market, which have been developed specifically for use on metal, in my opinion, none of them are as good as oil-based enamel. You can use those paints and they will stick to the project; but they probably won’t last as long.
Avoid spray paint whenever possible. Even the best spray paints are thinned considerably in order to get them to spray. That means you are applying a very small amount of solids to the project with each coat. You would need to apply two to four coats of spray paint, to equal one coat of brushed-on paint.
Home trim can either be stained and varnished, or painted, depending on your personal preference. If your home already has painted trim, you pretty much need to stick with paint. About the only way you can go with stain and varnish is to replace the trim. But the converse isn’t true, as mentioned above, you can paint over previously stained and varnished trim.
If you ever find yourself installing new trim, you’re always better off applying all but the last coat of finish, before installing it. That will save you a lot of time and a lot of careful “cutting” as you’re trying to finish the trim, without messing up the wall or vice-versa. Once the trim is installed, all you have to do is fill the nail holes and apply the last coat of varnish or paint.
Painted trim is intended to stand out from the wall, drawing the viewer’s attention. That’s why you see many modern homes which have fancy architectural moldings painted with darker walls, creating a greater contrast between the walls and trim. The other thing that makes it stand out is using a semi-gloss or even high-gloss paint.
Applications where Mold is an Issue
If you are working on a home which has a problem with mold, you need to deal with the mold, before painting. In most cases, mold can be killed with a 5% solution of normal household bleach, diluted in water. Spray or sponge the solution onto the wall, all it to soak, and then wipe the dead mold off.
To help protect against any stain from the mold showing through your paint, you should prime those surfaces with a stain killing primer, preferably a shellac based one. Shellac dries very quickly, helping to ensure that the stain cannot come through.
There are mold-resistant paints made for use in these situations. They have persistent chemicals added to the paint, which provide an inhospitable environment for mold, impeding its opportunity to grow on those surfaces.