Two of the most important factors affecting how paint dries are temperature and humidity. Knowing how to avoid adverse environmental extremes can help you avoid painting problems.
In extreme cases, bitter cold prevents drying altogether while heat has the opposite effect. When the temperature is hot, the surface of the paint can skin over before the lower layers have a chance to dry. Alternatively, when the products applied in excessively hot temperatures dry too quickly they can often develop bumps, blisters and other imperfections, such as lifting, cracking, or discoloration.
The rule of thumb is that if you are painting with an oil-based paint, the ambient temperature should be above 45°F or 7°C for at least 48 hours. Latex and acrylic paints typically require higher temperatures above 50°F or 10°C. Some paints, however, are formulated to dry at lower temperatures, even as low as 35°F or 2°C.
Lower temperatures can also cause issues. It’s also important that air temperatures don’t drop below freezing the first night after paint has been applied, since curing paint can still contain moisture that will crystallize in sub-freezing temperatures. Not only should temperatures be above 45°F or 7°C when the paint is applied, but they should remain that way for at least two or three hours for paint to dry properly.
In high-humidity situations, you could see what is called surfactant leaching: brown or white discoloration on the surface of the paint. If the paint is exposed to excessively high humidity, the desired protective qualities of the paint may be compromised. High humidity also works against a fresh coat of paint by reintroducing water into the incompletely dried paint film.
Humidity also needs to be considered when painting a wood surface. The wood can absorb the moisture in the air, which can compromise the adhesion of the paint to the surface, resulting in peeling or bubbling paint.
How Temperature Affects Drying
As temperature lowers, the paint thickens. The thicker the coating, the longer it takes for the paint to oxidize in the case of oil-based paints. In addition, when a coating is thicker, it extends the time it takes for the solvent to evaporate.
How Humidity Affects Drying
When humidity is high, the paint is exposed to a greater amount of water vapor, which affects drying not only of acrylic and latex paints.
How? With more moisture in the air, it takes longer for the water in an acrylic or latex paint to evaporate. When you combine low temperatures and high humidity in painting outdoor projects, for instance, condensation on the surface of the paint often occurs. This condensation can result in damage of the paint finish, like lifting, disadhesion and over paint failure.
Coating thickness is only one factor that affects the drying time of acrylic and latex paints. Beyond humidity and temperature, other weather issues such as wind and precipitation also affect paints and other coatings. Get the conversation started and make sure your paint job is done right by calling Raider Painting today. You are guaranteed an expert opinion of our team of experienced painting contractors.