Most exterior surfaces need two coats of paint over the primer or existing paint to be optimally durable, even if it looks fine with just one coat. To apply a second coat of paint, it's important to let the previous coat of paint dry, and the recommended drying time given on the label is merely a guideline. There are some instances where you need to wait longer than recommended, and others when it's OK to allow less time.
Instructions
Read the paint label directions for suggested drying time before painting a second coat because each paint is formulated differently. Wait at least four hours before applying water-based paint, and eight hours minimum before applying oil-based paint.
Pay attention to the temperature and humidity and choose warm, dry days for exterior painting. Allow more time than suggested on the paint label before recoating if weather conditions are less than perfect.
Mix together enough paint for the entire job to ensure color uniformity for the entire final coat. Use clean 5 gallon buckets to stir together single gallons.
Apply the paint to the siding with a brush, roller or paint sprayer. Mask the windows and apply the second coat with a sprayer for the fastest job, even if you rolled or brushed the first coat.
Paint the trim last using a brush. Use a 4- or 6-inch roller for rough wood trim. For a more professional-looking job, paint the returns (edges) as well as the face of the trim.
Tips & Warnings
Optimal drying conditions for paint are temperatures between 70 and 80 degrees F, with humidity at less than 70 percent and a slight breeze.
It's almost always better to paint two thinner, even coats than to paint one thick coat of paint.
Paint and hardware stores have gauges to measure surface temperature and humidity.
Always paint two coats of finish paint over primer.
Avoid painting too late in the day if the temperature is expected to drop below 50 degrees F because the temperature drop can result in poor adhesion between coats and an uneven finish.
Pay attention to the dew point when painting in cooler weather. The dew point is when the temperature, barometer level and ambient humidity come together to condense enough moisture in the air that droplets (dew) settle on surfaces. If moisture starts settling on paint before it's dried, it can get trapped between the layers of paint and cause a blotchy or uneven sheen. The surface temperature should be at least 5 degrees higher than the dew point.
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