Wet Paint, Wetter Weather

February 12, 2013

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Commercial painting and humidity

For any exterior commercial or industrial painting project, the weather has a definite effect on the process. It may seem that summer, with its warmer temperatures and more agreeable weather, is the best time to paint outdoors—but there are issues beyond the heat that risk ruining the finished project. Humidity can cause a number of difficulties and delays that commercial painting contractors must be prepared to deal with.

What happens when it’s humid

Humidity, or the moisture content in the air, can interfere with an exterior painting project. This weather condition is a frequent occurrence in California, since the humidity is higher when there is fog or mist present.

The biggest challenge that humidity presents is the drying process. Paint dries through evaporation, which is liquid leaving the paint—either water or solvent, depending on the base the paint uses. When the air surrounding the paint is saturated with moisture, evaporation is impeded because the liquid has no place to go.

A successful painting project depends on a steady rate of evaporation. The slowed evaporation process that results from humid conditions causes adhesion failure in the paint, which develops a dripping, sagging look instead of a sturdy, even coating.

How humid is too humid?

Many types of paint offer manufacturer’s guidelines that recommend an optimal humidity range for exterior painting. In general, however, the evaporation rate will be suppressed when humidity levels are above 70 percent, and the paint will not adhere properly.

With locations near the ocean, the humidity levels can rise above safe levels frequently during the heat of summer. Fog’s high humidity content also inhibits painting. Although it requires flexibility in scheduling, a skilled commercial painting contractor will not work outside in foggy or extrem

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