Take time to prep for paint success

Overall, a top-quality latex paint containing acrylic binders provides a high degree of adhesion to most surfaces. And good adhesion is the key to durability. Top-quality, oil-based paints also offer excellent adhesion, but there’s a trade-off. With the passage of time, depending on the substrate, weather conditions and the particular paint, oil-based products can become brittle and occasionally begin to crack in just a few years. Even so, the use of top-quality, oil-based paints is still recommended over a latex paint under certain repaint circumstances.

The first of these involves painting over heavily chalked surfaces. Oil-based paints tend to adhere better than latex paints to substrates that are excessively chalky. Of course, it is still important to properly prepare the surface by removing as much of the chalk as possible before painting.

The second instance in which top-quality, oil-based paint is preferred is when repainting a surface containing multiple (four or more) layers of oil-based paint. In such instances, the elastic latex paint can sometimes accelerate the adhesion loss that causes oil paint to become brittle.

To get the full benefit of any quality paint (latex or oil), it must be applied to a well-prepared surface — one where any dirt, chalk or mildew has been cleaned off, and one that is free of flaking. If any of these contaminants are present, the paint may not adhere properly. That could lead to future problems.

Remove loose, flaking paint by scraping and sanding. Wire brushing is also effective in removing it. If rough paint edges remain, continue sanding to feather them back. If the existing paint has a glossy surface, this should be sanded or brushed in order to dull the surface and provide more grip for new paint.

New, unpainted wood (or any bare wood) also needs proper surface preparation prior to paint applications. Begin by removing any dirt, oil, grease, wax or other contaminants with soapy water. If mildew is present, wipe down the surface with a bleach solution. Then rinse the surface thoroughly with clear water and allow it to dry. Surface imperfections in unpainted wood should be sanded and primed. Then apply a primer over the entire surface to provide a sound, stable base for the top coat.

When repainting a surface, primer is usually not needed unless the paint is very chalky or the bare wood is exposed. Good surface preparation stretches the life of any paint job, and is the key to success. If sanding or scraping is required, be sure that the surface is wiped clean of all residue and dust prior to painting.

In the past, it was not advisable to apply a latex paint over an oil-based product. However, with improved technology, today’s acrylic latex paints are formulated to provide excellent adhesion to alkyd substrates. You should be able to use a quality acrylic latex exterior paint, unless there are multiple coats of oil-based paints on the existing surface. In such cases, it is not advisable.

One last important point: You should choose quality paints. Although more expensive, they have better durability, color-retention and will save you problems and expense in the long run.

For more information on paint, visit The Rohm and Haas Paint Quality Institute at www.paintquality.com.