Part 2: Wear, Substrate, And Surface Preparation Are Key Factors In Paint Longevity
Wear, Substrate, And Surface Preparation Are Key Factors In Paint Longevity
By David Lewellen March 2014 - Paints & Coatings
4. What kind of wear or abuse will the area see?
"A corridor hallway has to have a lot more resistance to abuse than a judge's office," Law says. Coatings on handrails need to be ultra-high-quality, because "the oil in human beings eats into paint," Law says. Even on a project that is almost all water-based paint, Law recommends alkyds for doors and frames. One way to reduce wear on a door, Law says, is to install a metal push plate, so that hands don't come in contact with the coating.
In a bathroom or an office kitchen, or almost any hospital setting, walls need to be cleaned regularly, and the paint choice needs to reflect that. Zimmer suggested talking to paint contractors for feedback and suggestions — based on callbacks, they are likely to know what will endure. Crissinger added that manufacturers' performance data offers guidelines, too; an ASTM standard measures a coating's scrubbability. A qualified contractor can help in interpreting the information on the label or spec sheet.
5. What's the substrate?
Metal, brick, masonry, and other substrates offer "wonderful painting opportunities" on exteriors, says Zimmer. "They're terrific substrates to use 100 percent acrylic." She cautions that outside, a top-quality paint is necessary for "better tint retention, better prevention of peeling and flaking." Buildings in the North need a paint that will expand and contract in freeze-thaw cycles; in southern areas, resistance to color fading is important.
Almost any substrate used on exteriors may also be found inside, as well as drywall or trim, but the appropriate paint choice may be different. Law's group, the Master Painters Institute, has helped to develop a free online decision tree that can help identify appropriate products; the work was done in cooperation with the National Institute of Building Sciences (NIBS). Beginning with the first division between interior and exterior, the tool takes users through the various substrates. At the bottom level, it discusses surface preparation and appropriate families of products, and offers links to standards. The tool is available at www.wbdg.org/tools/apsdt.php?c=5.
Law says that NIBS is also working to develop a similar decision tree for maintenance: "You don't know what the drywall will be like after it's been painted 28 times."
6. How will the surface be prepared?
"It's the most important part of the paint job," Zimmer says. "A quality painter will have it written into the contract that they will prepare the walls for application." That should be part of any conversation on a walk-through before the bid is submitted.
"Poor surface preparation can make good paint fail, but good preparation can improve a marginal paint's performance," Crissinger says. He estimates that of the paint failures he is called to assess, 75 percent are due to surface preparation.
It's particularly important in re-painting. "You have to be concerned about the quality of the product left on the surface," Law says. If the old coat is intact, it's possible that it may be "too smooth to paint," Crissinger says, and the surface will need to be abraded. If the previous coat is damaged, Crissinger says that a contractor's bid should include specifications that the company will remove as much as possible, and feather off sharp edges of remaining paint. Also, paint with a higher gloss level being applied over a previous, lower-gloss coat will not hide any imperfections in the previous coating.