When Painting, Watch the Temperature
As the days grow shorter and the nights grow cooler, you may suddenly realize that you only have a few weeks left to finish your exterior painting projects. However, beware of painting outdoors when the weather turns nippy. Painting when the weather is too cold is a mistake that will leave you with unsightly consequences.
Most manufacturers instruct homeowners to apply solvent-based paint when ambient and surface temperatures are above 45 degrees F and latex paints when ambient and surface temperatures are at least 50 degrees.
Solvent-based paints thicken in lower temperatures, causing stiffer brushing, heavier application and slower drying. This can mean paint runs, sags and wrinkling on vertical surfaces, plus an overall reduced rate of coverage per gallon.
Below 50 degrees, latex paints dry more slowly, especially when high humidity is present. This hinders coalescence, which can lead to poor film-forming, lack of surface adhesion and premature paint failure.
Some manufacturers offer latex paints that can be applied at temperatures as low as 36 degrees F. These specially formulated products contain coalescing agents that aid in film-forming during lower temperatures. Check with your local independent paint retailer for information about these products.
Another thing to consider about seasonal painting is the amount of daylight. When the days are short, there is less daylight available to aid in drying. If you're using a solvent-based paint, which dries by oxidation, daylight is especially critical. So, be sure to paint early in the day so that light is present to add in the drying process.
Also consider the effect of heavy dew. Humidity affects the drying time of all paints, but especially latexes. Most manufacturers recommend that at least two hours be allowed for paint to dry before sunset if cool temperatures and heavy dew are expected that evening.
Finally, keep in mind that cooler temperatures may extend the time before the paint reaches serviceability or hardness. An enameled door requires more time before it can be closed without sticking to the jamb. A clear coating applied to a deck will need more time before you can walk on it. Primers require more time before top-coating. Knowing all of this may aid you as you go about your painting chores in the spring or in the fall.
When in doubt, remember to call your local paint and decorating retailer for advice and assistance.
Courtesy of the Paint and Decorating Retailers Association - www.pdra.org