Paints are classified by the resin type. Resin types include oils/alkyds, latex/acrylic, epoxies, and urethanes. The most common types are oil and latex paints. One of the differences between oil and latex paint is the curing time. Oil can take up to 10 days to dry. While latex may be dry to touch in two to four hours, it can take up to 30 days for a maximum cure.
There are several curing mechanisms for paint. In solvent evaporation, evaporation of the solvent allows the paint to dry. With coalescence, particles of pigment and binder fuse together. Oxidation has binders that oxidize because the binders react with oxygen in the air. Drying is one stage in which the solvent evaporates. Curing is a later stage when the coating reaches the optimum hardness.
Curing is affected by a number of factors. This includes temperature, air movement, relative humidity, and dew point. If there is too much air movement, this can result in flash drying and the paint may crater. A key component in a good paint job is proper surface prep. Preparation prevents problems and is critical for wood and metal applications.
Wood usually requires a protective coating applied on a clean, dry surface. Any holes and cracks should be filled before applying the coating. Before starting, check the painting process for the type of wood. Most types of woods should be powerwashed 48 hours or more before coating. Also, if it happens to rain all week, don’t paint the next day as the additional moisture in the air might negatively affect the result. Staining wood should be done on a clean and dry surface. Before staining, set nails below the surface and fill in these area. Also remove any loose fibers. If the wood was stained previously, strip the old finish before restaining. A wood bleach system may help to achieve an even color. If using a clear finish, apply a minimum of four coats.
Surface porosity and PH are important to consider when painting masonry. Filling of the masonry should be done on highly porous masonry. Also, painting hot masonry will burn the resin. This will cause the paint not to adhere properly to the surface. However, this problem might not be evident until the next season as the paint separates from the stone or cement work. In addition, concrete should not exceed 9 or 10 PH after 90 days of curing.
Metal can be painted with latex or waterborne acrylic for galvanized steel. Be sure to remove any shipping coats of oil or paraffin before applying any coats of paint. Whether painting masonry, wood, metal, or another surface; the first coat of paint is the most important for the life of the substrate.
Protection of the surface from the environment is the driving factor when selecting paint. People also paint to add color that matches their mood or enhances the safety of the environment. Another factor is the selection of a sheen that delivers both appearance and performance. Finish coats combined with the color wheel to offer common color schemes like monochromatic, analogous, and triadic. Monochromatic color schemes are tints and shades of a single hue. Analogous color schemes are three shades next to each other on the color wheel. Triadic color schemes are three colors that are equidistant from each other on the color wheel.
When ordering paint selections, both the product and the sheen must be noted in writing the specifications. Sheen varies from matte to high gloss. Glossy sheens have extra durability, high gloss show defects more, and flat paints tends to hide imperfections. Lower sheens are more easily cleaned and soften the room. In a residential setting, paint is usually selected for usability on the interior and protection on the exterior. In commercial settings, coatings are also selected for chemical and wear resistance. Two component coatings can offer chemical and abrasion resistance. Besides the standard paints that are available, specialty paints may offer spray application, low VOC emission, splatter resistance, and extreme durability.