Professional painting contractors often engage in discussions about their favorite paints and favorite paint jobs. Often those conversations turn to proper paint selection and understanding how to avoid premature failures. With this article, we look at several of the factors that influence paint failure and a few of the more common paint problems that may result.
Film Thickness and Uniform Coverage: Thicker films are desirable for some obvious reasons. Since coatings provide barrier properties, one can envision that thicker films would help prevent moisture, UV light and other harmful elements from getting to the surface. In the case of bare wood and masonry, thicker films can better absorb changes in the surface, while thin film coatings tend to crack as the substrate moves. Thicker films generally provide for better hiding and stain blocking, as well as better mildew and corrosion resistance. Nonuniform paint coverage (resulting in peaks and valleys) can enable dirt buildup on the coating.
B. Substrate Effects: The type and condition of the surface to be painted significantly influences the paint selection. The marketplace has evolved to offer products engineered for specific substrates. Most manufacturers today offer products that are uniquely suited for wood and masonry applications. With aged and weathered substrates, proper surface preparation becomes critical to avoid premature failure. It is extremely important to paint on a surface with no loose or foreign particles. Appropriate techniques, e.g., power washing, must be employed to remove those loose particulates from the surface. We recommend the use of an appropriate primer as well.
C. Impact of Priming: The use of a proper primer is essential to ensure that the paint finish delivers acceptable performance over the lifetime of the paint. Priming needs will vary depending on the substrate and conditions under which the paint is applied. For this article, we focus on the role of priming in enabling adhesion and providing a uniform appearance. Primers are especially important when painting over aged or chalky surfaces. Quality primers provide good adhesion and result in the longer durability of the topcoat.
D. Adverse Weather Application: The emulsion used in water-based paints consists primarily of spherical particles dispersed in water. In a fully formulated paint, these emulsion particles are mixed with pigment and other additives. After the paint is applied and it begins to dry, the pigment and binder particles come closer and closer together, until ultimately the binder particles fuse and bind the particles into a tough, “continuous” film. Painting under adverse conditions can impact this film formation process and result in premature cracking and flaking. Before painting under stressed (e.g., low temperature) conditions, we suggest you review the manufacturer’s recommendations. More recently, paints have been introduced that allow for painting as low as 35° F – prudent manufacturer’s guidelines must still be followed to avoid pitfalls during these low temperature applications.
Product choice (and more important, ingredient choice) remains the other key component in ensuring a quality paint job. To assist you further with proper product selection for a given job, we encourage you to review our step-by-step guidelines at www.paintquality.com.
Foaming or Cratering: Formation of bubbles and the resulting small, round, concave depressions when those bubbles break during paint application and drying.
All paints will foam to some extent during application; however, higher quality paints are formulated so bubbles break while the paint is still wet, allowing for good flow and appearance. Apply gloss and semigloss paints with a short nap roller, and apply a sealer or primer to porous surfaces before painting.
Brush and Roller Marks from Poor Paint Flow and Leveling: Failure of the paint to dry to a smooth film, resulting in unsightly marks or patterns after the paint dries.
Use high-quality paints to prevent this problem from occurring. Quality paints contain ingredients that enhance paint flow and form a smooth film.
When using a roller, be sure to use a cover with the recommended nap length for the type of paint being used.
Use a high-quality brush; a poor brush can result in poor flow and leveling. APC