Painting in cold weather

For the purposes of painting, cold weather is generally defined as temperatures below 50 degrees. In New England weather drops below that temperature regularly starting in October but you can get some exterior painting done if certain rules are followed.

What Cold Does to Paint

Temperatures below 50 degrees can have a variety of harmful effects on paint and paint application. Alkyd and oil-based paints are made with oils and resins that become more viscous at lower temperatures which can make it very difficult to apply the paint evenly or smoothly. Water-based, or “latex,” paints are made with water and are thus are susceptible to freezing in cold weather.

Both alkyd/oil and water-based paints are formulated to cure within a specific temperature range and may not cure properly at temperatures below that range. Improper curing can lead to a number of problems, including poor coverage, blushing, peeling, bubbling, cracking, low sheen, and color inconsistency.

Is Previously Frozen Paint Usable?

Water-based paint that has gone through several freeze-thaw cycles may still be usable, but not always. If a previously frozen paint is lumpy and will not mix to a smooth consistency, it is no longer usable. This indicates that the paint has lost its ability to emulsify and is incapable of curing properly. Water-based paint freezes at 32 degrees, while oil-based paint is much more resistant to freezing but can still have difficulties with lower temperatures.

Recoating in Cold Weather

Cold weather slows the drying time of both alkyd/oil- and water-based paints. This means that recoat times are also extended. For example, at an ideal temperature of 75 degrees, you can usually recoat after four hours. But when the temperature is about 50 degrees, the recoat time may be extended to six hours. Painting in cold weather using alkyd or oil paints requires even more time—in some instances, more than 48 hours before recoating. This is an important consideration when painting the exterior of a house.

Note that direct sunlight or shade can cause surface temperatures to vary between different areas on the same structure. In cooler temperatures, the sun can have an even more dramatic impact on the temperature of the structure.

The Best Paints for Cold Weather

Many major paint manufacturers offer special paints that are formulated for cold weather. Most of these are rated for temperatures no lower than 35 degrees. It’s best to use one of these paints if your project must be completed in cold weather. A paint that’s designed for lower curing temperatures is more reliable and will give better results than standard paints mixed with additives for freeze-resistance or thinned for easier application.

Note that the temperature must be at or above the minimum recommended curing temperature for the entire curing process, not just during application. If you add a fresh coat of paint in 45-degree weather, but then the weather turns colder an hour later, the paint may not cure properly even though it will eventually dry. Adding coats can be very challenging as the temperatures fall in the later afternoon or evening.

Tracking the Weather and the Sun

Before beginning work on your project, check local forecasts and find a stretch of a few days when temperatures will be their highest and the sun will be out. You’ll need to have a few days in a row when temperatures don’t drop below the minimum for the paint you are using because you also need to factor in drying time for multiple coats.



 

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