For interior and exterior painting projects, the matter of what temperature to paint requires careful consideration. If you make the wrong decision, you risk premature paint failure. It’s easy to decide not to paint during an extreme heat wave or when it’s freezing outside. Paints, like materials, react to changes in temperature and humidity. Excessive moisture or a temperature that is too hot or too cold will cause the paint not to cure properly. The last thing you want to do is find yourself repainting your house because the conditions worked against you.
How the Temperature Affects Painting
If you paint your house when the temperature is too hot, the paint dries too rapidly, and the heat compromises adhesion. At temperatures over 90 degrees Fahrenheit (F) / 32.222 degrees Celsius (C), the paint forms bubbles and blisters. Once the paint cures, it starts peeling. Cold weather painting, when the temperature drops below 55 degrees F 12.778 degrees Celsius (C), effects the speed at which the paint cures. When the paint takes longer to dry, the wet surface attracts insects, dirt, grime and other debris.
Improperly cured surfaces also have a higher propensity to cracking peeling and chipping, and cold weather reduces the overall life expectancy of the paint. Something else you should consider regarding a low temperature for painting, oil-based paint thickens. Thicker paint causes stiffer brushing, heavier application and less coverage per gallon.
What Temperature to Paint Outside
For exterior paint projects, the best temperature for painting with latex falls between 50-70 degrees F / 10 – 21.111 degrees C, and 45-90 degrees F / 7.222 – 32.222 C when applying oil-based paint. Always ask your local paint expert to decide if you really can paint in the weather conditions anticipated for your project or if you should wait for more suitable temperatures. Most paint manufacturers make the following recommendations for minimum temperatures:
- A minimum ambient and surface temperatures of 50 F / 10 C degrees for latex paint when painting outdoors.
- For solvent or oil-based paints, the ambient and surface temperatures must rise above 45 degrees F / 7.222 C, for a minimum of 48 hours.
To avoid painting in direct sunlight and on overheated surface materials outside, painting outdoors, most experts recommend that you follow the sun around the house. Allow time for the paint to dry to the touch before sunset, cooler temperatures and the formation of dew.
If you must paint in lower temperatures, purchase the specially formulated latex paint made to perform in temperatures as low as 36 degrees F / 2.222 C. This paint contains coalescing agents that bolster film-forming attributes during low temperatures.
Account for Humidity When You Paint
Humidity refers to measurement of the water vapor in the air. Excessive moisture in the air results in the formulation of water vapor on the freshly painted surface and incompletely dried film. Painting in a high humidity environment can result in the problem of surfactant leaching whether you use latex or oil-based paints. Leaching occurs when white or brown discoloration appears on the surface of the paint. Excessive humidity can also compromise the paint's protective qualities.
When painting a wood surface, you must consider humidity because the wood absorbs moisture from the surrounding air. This process impedes adhesion of the paint to the surface and causes the paint to bubble and peel. One of the benefits of interior painting has to be the ability to control the climate. You can get rid of excessive humidity by running a dehumidifier or the air conditioning unit.
If you have questions about when you should begin your painting job, give the professionals at Five Star Painting a call. We’re happy to provide you with all the information you need to make the right decision.