How to avoid fast drying of exterior paint

Film formation and durability can also be affected if latex paint dries too quickly. That’s because fusion or coalescence of the latex binder takes some time to occur properly. Very quick drying can reduce the mobility of the particles before the film is adequately formed. Conditions that make latex paints dry too quickly can thus compromise film formation, even though the paint may look fine.

Conditions that contribute to overly fast drying of exterior latex paint include:

•	Painting when the temperature is too high. Avoid painting in temperatures over 95°F.
•	Painting in direct sunshine. Even on a moderate day, it is best to avoid painting in direct sunshine because surface temperatures can be 10 to 20 degrees higher than the air temperature. And the paint itself can be heated by direct sunshine, especially if it is a dark color. To avoid this, work your way around the house or building so that you are always painting in the shade, especially in the warmer afternoon hours. As a bonus, you’ll be more comfortable working this way. Where this can’t be done, try to paint these areas in the early hours of the day.
•	Painting in dry and/or windy weather. Even light wind can cause latex paint to dry very quickly, contributing to inadequate film formation. This effect is compounded when the relative humidity is low, below 20%.
•	Painting a very porous surface that absorbs the water from the coating. If painting porous masonry, apply a sealer first. Or, if using a 100% acrylic paint, dampen the masonry just prior to painting. This will retard the drying process.

If possible, avoid painting when more than one of these conditions that could excessively speed drying is present.