Glaring imperfections, offensive odors, and poor adhesion are all signs of a bad paint job. With a basic understanding of the properties, characteristics, and application methods of interior paint, your next project will look great and deliver the performance you expect. The more knowledgeable you are, the better you'll be at articulating your needs to in-house or outsourced painters; you'll also understand the rationale behind their recommendations. With paint problems resulting in cost overruns, lost productivity, and bad first impressions from visitors, whoever said ignorance was bliss clearly wasn't referring to paint. Familiarity with your options puts you one step closer to a job well done.
Oil-Based vs. Water-Based Paint
When it comes to picking paint, selection begins with choosing between oil-based and water-based paints. For hundreds of years, people have been using oil-based paints for their impermeability and toughness.
Unlike water, oil does not dry by evaporation. It dries through a process of oxidation that converts the oil into a polymer chain. This means that the layer formed will be resilient and long lasting, and will withstand the degenerative effects of water and air longer than water-based paints. There are, however, several disadvantages to oil-based paints. First of all, oil paints take longer to dry than water-based paints, have a strong odor that lingers long after the paint has been applied, and contain volatile organic compounds (VOCs).
The paint pigment in oil paint is suspended in the solvent. VOCs are found in this solvent and are released as the paint is drying or being cured. VOCs are harmful to occupant health and the environment. Indoor air pollution has now been identified as being three times more harmful than pollution outdoors. This is mainly due to the release of VOCs by oil-based paints and other off-gassing interior VOC-containing finishes and furnishings. Government regulations regarding VOCs are becoming stricter; this may be one reason why oil-based paints are decreasing in popularity.
As opposed to oil-based paints, water-based paints (sometimes referred to as "latex paints" or "acrylic paints") do not use solvents; the carrier for the pigment is primarily water. Latex paints have come a long way from when they were considered an inferior replacement for oil-based paints, and they're now on the verge of dominating the market. The advantages of latex paints are many. The drying time is significantly shorter than oil-based paint, which requires up to 48 hours to dry, leaving the room unusable during this time. Latex paints also have a minimal odor and release significantly fewer VOCs during the drying process.
Because fewer or no VOCs are released, latex paint is significantly less harmful to building occupants. In addition, it requires less care to apply than oil-based paint and solvent, which are both highly flammable. Latex paint can also be thinned with water, unlike oil-based paint, which requires a special thinner.
Picking the Right Paint Finish
Beyond oil- and water-based categorization, paints can also be classified based on their function (e.g. primers, sealers, binders, finishing paints, etc.). They can also be classified according to the type of pigment used, like zinc, lead, and titanium (each has slightly different properties). But, by far, the most important classification of paint is the one that provides information about the type of finish.
With the traditional application of paint, the finish reveals how the paint reflects light once it's dry. An exception is when special painting techniques (e.g. faux painting) are used, since these lend a completely different finish. Generally speaking, in commercial buildings, the finish depends solely on the type of paint used.
Certain finishes are more appropriate for certain rooms; this is because each finish has certain properties, apart from the way it looks, that distinguish it from the other finishes. Finish options include:
Matte. A matte finish reflects light poorly. It's a rough finish that's generally considered to be warm and comfortable. Matte finishes are not slippery; therefore, they don't wash very well. For this reason, it's not recommended to use a matte-finish paint on walls in rooms that have frequent visitors (e.g. a reception area or a conference room). The best places to use this finish are in executive offices or boardrooms: places where only a few people use the room, and the chances of dirtying the walls are low. Matte finish is great for hiding imperfections in the walls because highly reflective paints draw attention to imperfections by creating a crack in the uniform light reflection. Matte paints inherently avoid this problem.
Flat enamel. If you want to have the look of a matte finish in a bathroom or a café, consider paint with a flat-enamel finish. This paint holds the same properties as the matte finish, with one exception: It's more washable. Unfortunately, paints with enamel finishes contain extremely strong chemicals and can exude an odor for several days.
Eggshell. The next paint on the curve of reflective properties—the eggshell finish—has a decent amount of sheen. If you can imagine looking at an eggshell in the light and seeing how the light bounces off of it, you'll have a good idea about what this finish will look like. As expected, the eggshell finish is easier to clean because of its slight gloss.
Satin. A satin finish is glossier than an eggshell finish, and it's even easier to keep clean. Due to their dirt resistance and ease of cleaning, the usual choices of location for satin finishes are halls and stairways. The finish gives a velvety shine to the surface and will not hide imperfections.
Semi-gloss. Semi-gloss paints have a high durability and a good amount of sheen. They are best used on surfaces like doors and trim. Due to their high water resistance and ease of cleaning, they are also an excellent choice for painting the walls of kitchens and bathrooms.
Gloss. At the high end of the reflective gradient are glossy paints, which are rarely chosen for interior walls due to their extreme shine—any imperfections will glaringly stand out. It's best to use them when painting floors and trim; the finish is extremely durable.
Prepping the Surface
Painting a room is more than just taking out a brush and applying the paint. It‘s a well-known fact that a good paint job is 80-percent preparation. This holds true whether you're painting office walls or an entire building. Try painting a ceramic tile by directly applying the paint; you‘ll find that the paint just doesn't stay because the ceramic tiles are smooth and glossy, and don't give the paint any grip. The role of the top layer of paint is primarily to provide color. It's not made to have great adhesion or protection value. To get paint to stick to any surface, you need to use a primer. A primer is a layer of paint that's applied before the topcoat. It's designed to stick to almost anything. Once this is laid down and dried, the topcoat of paint is applied; this time, it'll hold.
Having a good primer is, however, only part of the process. All surfaces need to be prepared to receive paint. The type of preparation depends on the surface. Wood needs to be planed and sandpapered. Depending on whether it's hardwood or softwood, you may need to get rid of knots that will exude resin and spoil the paint job.
If the paint is being applied to metal, the most important step is removing any grease. This can be done with a liquid de-glosser. Rust must also be removed. Specific rust cleaners containing oxalic acid are made for this purpose. If pipes that contain hot water are being painted, then the paint needs to have special properties that enable it to withstand heat.
Applying the Paint
It's almost always necessary to paint a surface with more than one coat, and there are several reasons for this. The main reason is to get the full color that you want. With just a single coat of paint, you might be able to see a glimpse of the original color underneath. Also, two coats are more durable. In addition, the second coat of paint allows you to cover up what may have been missed during the first pass. In general, the second coat of paint can extend the life of the paint job by a factor of three. As a rule of thumb, two coats of paint are accepted to be enough for a surface.
As mentioned in the discussion of oil and latex paints above, the time the paint takes to dry depends on the drying process. If you're using latex paints, the drying process takes place by evaporation and is, therefore, much faster—maybe as quick as 1 hour. Oil-based paints, however, don't dry in the conventional way: They are cured, and this can take several days. Since it's necessary to wait for the first coat of paint to dry or cure before the second coat is applied, your paint job will either be hastened or delayed, depending on the type of paint being used.
Various surfaces require different painting techniques. Additionally, some surfaces take well to certain paints. Painting drywall surfaces is fairly straightforward. Drywall (also known as gypsum board, wallboard, or plasterboard) is a panel of gypsum surrounded or lined with paper. Drywall surfaces take well to water-based paints, and any finish will look nice, apart from a glossy finish.
Painting block surfaces, such as masonry or stone, is problematic because the surface is often uneven. Several pores and cracks make it impossible for a primer to do its job properly and fill them in; therefore, block filler, a paint-like material that smoothes out uneven or porous surfaces, is necessary. It's also used on concrete blocks. While block filler isn't very durable, it's possible to use it as a finishing coat by itself. It's recommended, though, that a more durable finish, like eggshell or semi-gloss paint, is applied after the block filler.
For metal surfaces, consider using latex paints. Due to the latest advances in paint manufacturing, water-based paints have now become a viable alternative to oil-based paints, and are often preferred due to their environmental friendliness. (In the past, water-based paints promoted the formation of rust on the metal through oxidation.) To paint metal that has been previously coated with an oil-based paint, the metal must be properly prepared by being de-glossed and coated with a latex-bonding primer. Glossy finishes, like satin or full-gloss paints, are typically used for painting metal surfaces due to their ability to protect against water and mold. Another good option for metallic surfaces is an epoxy coating.