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Weather conditions, such as temperature, humidity and air movement can have a significant impact on the overall appearance and performance of an exterior paint job. The quality, continuity and uniformity of the paint film will be determined by the temperature and drying conditions. Some of the factors affecting the drying rate of waterborne acrylic coatings are:

Humidity: high relative humidity (moisture content of the air) retards evaporation of water from the paint. Relative humidity above about 90% can cause extremely slow drying. Excessive humidity can also lead to sagging of the paint, especially at higher wet film thicknesses.

Temperature: low temperatures impede evaporation of liquids from paint. Significant slowing of dry is generally observed with temperatures below about 60°F, but with care waterborne acrylics can be applied down to 45°F. Temperatures above about 95°F can lead to the paint drying too fast. Painting in direct sunshine can dramatically increase paint temperature (and thus speed of dry) if the paint is a dark color, which absorbs heat from the sunshine. High surface temperatures, whether due to exposure to sunlight or service conditions (e.g., hot pipes), will also lead to increased speed of dry, and can cause mudcracking, dry spray, and difficulty in maintaining wet edge.

Wind: air movement speeds drying because fresh air passing over a wet paint helps liquids in the paint to evaporate. Dry times are generally specified assuming little or no air movement. In high humidity situations, some air movement can be helpful and will aid in the drying of a waterborne paint. However, in low humidity conditions (below 20%), even a light wind can cause the paint to dry too rapidly.

The effect of the environmental conditions on the drying speed of a waterborne paint have an impact on performance because of how it affects the film formation process. Manufacturer’s recommendations for temperature, humidity and air movement should always be followed for any paint to insure its optimum performance. For info on possible problems which can occur when waterborne coatings are applied outside of these intended limits, click here.

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