Certainly, you need cooperation from the weather when it comes to exterior painting of your house or out buildings. The weather should be clear, with no threat of precipitation, and very little wind. A light breeze is fine, but anything stronger and the air movement can adversely impact the final results of your work.
As a general rule, temperature should be above 50°F (70° is ideal) and no higher than 85 or 90°F for best results. It is also helpful if the humidity is less than 60%.
Obviously, you want to avoid rain for as long as possible after the paint has been applied, and you should try to avoid painting any surfaces that are in direct sunlight.
But what about the temperature of the surface you are painting?
Did you know the temperature of the side of a house on the north side in early morning can be twenty or more degrees cooler than the relative air temperature? So if your target to begin painting is when the air temperature reaches 50° or 60°, if you are starting on the north side of the building, you may be starting before the surface temperature has warmed up to be within the correct temperature range for application.
In the same way, if you move to paint an area that has just been in the full sun and is now in the shade, the surface temperature may be well beyond the upper limits for a quality outcome.
Surface temperatures have a serious impact on the longevity, look and adhesion of paint finishes. Too cool or too hot can impact the bonding that happens chemically between the paint and the surface being painted, leading to problems such as bubbling, peeling, cracking or the build up of moisture under the paint surface.
Simple tips to follow are to paint in late spring or early fall, typically well after the last spring frost date and two to three weeks before the first expected fall frost.
Avoid painting close to sunset on days with evening and overnight temperatures below 50°F as you want to give the paint adequate time to dry for at least two to three hours before temperatures begin to fall and/or dew begins to rise.
Use your eT650D infrared thermometer to determine the precise temperature of the surface you are about to paint. Particularly surfaces which have not yet been warmed by sun in the morning or surfaces which have recently gone into shade after sun exposure. It is a good idea to sample the temperature across a given surface, as cooler areas can be found near vegetation, in shaded areas or closer to the ground.
Try to apply paints when the surface temperature is as near to 70 degrees as possible. In some instances, this will require that you begin painting as soon as the dew is dry to give the paint time to set before it is exposed to the sun. Sometimes, an overcast day with very low chance of rain can be your best painting day, so long as the humidity doesn’t get too high.
There are other factors which affect the temperature of an exterior surface as well. For instance, an aluminum surface may heat up much more quickly in the sun than a stucco, plastered or wood surface. Each surface is different and requires different preparation and considerations before painting can begin.
Window washing follows the same general rules as painting when it comes to sunshine and temperature, but there are some key differences.
When you are washing large windows, especially if you are spraying them down from the outside, it is critical to determine that the water temperature of the sprayer is fairly comparable to the temperature of the glass. A cold garden hose sprayer aimed at a hot pane of glass can cause the window seal to rupture and can even cause the glass to break.
There is less risk of breaking the glass with water hot from standing in a garden hose in the sun, but any dramatic temperature differential between the water and the glass can cause leaks and ruptures to sealed solid install windows. Removable windows are less problematic, and can also be taken out of their window frames for easy washing indoors.
Always wash windows that are on the shady side of the house; and try to wash windows before they are exposed to sunlight or at the opposite time of day from their sunlight exposure. For example, east facing windows can be washed around the time of sunset and vice versa.
Washing windows that are in direct sunlight can not only break the window (see above) it also generally leads to smearing and streaking as the sunlight and relatively higher temperature of the glass dries the cleaning liquid too quickly before it can be properly wiped clean with a squeegee, newsprint or rag.
Your eT650D temperature gun can give you accurate readings for any window glass surface, and you may find that a single pane of glass has a range of temperatures where sunlight, shade or reflective surfaces nearby impact the glass. A sunny southern exposure with a wooden deck surface can easily reach 130°F on a sunny day, and a window which overlooks that deck can get to temperatures nearly as high, particularly if the window extends down to the floor level. The heat from the deck will literally bounce up onto the glass.
Don’t assume that because you are washing the interior of a window that it is not as hot as the outside of the window. Glass conducts heat readily, which is why we need double-paned windows to at least work to reduce heat and cooling loss through windows. As a general rule, as in painting, you want the glass as close to a mean room temperature of 70 degrees as possible when washing windows, and slightly cooler exterior temperatures when using an outdoor hose attachment and sprayer for window washing.
No matter what exterior painting or clean up job you are getting ready to tackle around the home, you’ll find the perfect tool to help you get all the information you need before you begin is the ennoLogic eT650D dual laser thermometer.