Uncommon exterior paint problems

Many problems associated with paint—such as peeling and flaking, chalking, and mildew—are common. These problems are typically a normal part of the aging process of paint. However, uncommon paint problems often appear suddenly, and their unusual nature can make them a source of concern.

Some of these problems can occur while the job is in progress, which creates some anxiety on the part of the customer. However, an understanding the cause of these problems and how they can be resolved can greatly diminish those concerns.

One of the more unusual problems is “re-wetting”. As the name implies, this involves a paint film that appears dry turning back to a liquid state, or re-wetting. The cause is cool, humid weather.

While most exterior paints are weather-proof within hours of application, cool, humid weather can slow this process. The surface of the paint film may appear dry, but the paint under the surface remains liquid. Given the right conditions, such as the temperature reaching the dew point, the surface of the paint can return to the liquid state.

Re-wetting has no impact on the performance of the paint. However, it can create issues with the appearance of the paint, as runs and sags may result. Fortunately, these can usually be corrected simply by using a roller or brush to spread the paint.

Re-wetting usually occurs in the late fall and winter. Monitoring weather conditions—and stopping paint application when conditions warrant—can help prevent re-wetting.

A second uncommon problem—surfactant leaching—can occur under similar conditions. This occurs when surfactants in the paint rise to the surface of the paint and are deposited there. When they dry they can leave unsightly streaks. Again, these have no impact on the performance of the paint.

Surfactant leaching can usually be corrected by lightly washing the area and repainting. In extreme cases a coat of primer may be required to prevent the stain from bleeding through the subsequent coat.

A third uncommon problem—the formation of bubbles—can occur when fresh paint is subjected to rain. This typically happens within the first twenty-four hours of application, and usually requires a relatively heavy rain to occur.  Such rains can force water into the paint film (latex paints are permeable by water, particularly before fully curing). When the water gets trapped between the paint film and the substrate, a bubble can form.

Small bubbles will usually correct themselves as the moisture migrates out. More severe bubbles may need to be broken to allow the water to escape.

The ideal way to prevent these problems is to avoid painting when conditions might be favorable for their development. However, this is not always possible or practical. Sudden rain storms, for example, cannot always be predicted.

While unsightly and a cause for concern, all of these uncommon problems are easy to correct. Perhaps most important, none have an impact on the performance of the paint.

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