In painting operations, attention should be paid to the effects of season and weather

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Different types of coatings and their various varieties all require application and drying under appropriate coating conditions to ensure the best coating results. Our country has a vast territory, with significant differences in climate conditions across various regions, as well as variations in temperature and humidity throughout the four seasons. Generally speaking, under natural conditions, when the temperature is high, the coating dries faster; when the temperature is low, the coating dries more slowly. A relative humidity below 70% has little impact on drying, but when it exceeds 70%, it has a significant effect on the drying of the coating film. Therefore, for coatings of the same type, their drying rate after application will vary between different locations. For example, Beijing has lower temperatures and is drier, while Chongqing has higher temperatures and higher humidity; as a result, the coatings dry more quickly in Beijing than in Chongqing. Different seasons, variations in temperature, intensity of sunlight, humidity in the air, and changes in weather conditions all have a significant impact on the drying of paints. Spring and autumn feature ample sunlight and relatively stable temperatures, making them the ideal seasons for outdoor painting work. However, painting should be avoided in conditions with winds of force 5 or higher, as dust and sand particles sticking to the paint film can affect its quality. In summer, the temperatures are high, the sunlight is intense, the humidity in the air is high, and there are many rainy days. While higher temperatures and sunlight facilitate the drying of the paint film, painting should not be carried out under extremely hot and sunny conditions. Because under intense ultraviolet light, the surface temperature of the coated object rises significantly, which can lead to defects such as orange peel texture, wrinkles, pinholes, and bubbling after the coating dries; therefore, it is best not to carry out work around noon in summer. In winter, when temperatures are low, sufficient sunlight and good ventilation have little impact on painting operations; however, the coating dries more slowly. To accelerate its drying, some drying agents can be added. In wet and cold weather, moisture will condense on the surface of the coated material, and cold winds can cause the coating to lose its luster, affecting its durability. In winter, when the temperature is between 5 and 10°C, work should generally be carried out between 10 a.m. and 3 p.m.; painting operations are generally not advisable when the temperature is below 5°C. Another scenario occurs under conditions of high temperatures and high humidity; due to the rapid evaporation of solvents in the wet coating film, or the extensive evaporation of solvents with strong dissolving power, the coating may sometimes become dirty and lose its luster. At this point, it is appropriate to add some high-boiling-point solvents with slow volatility, such as desiccants. In rainy weather, if the applied coating film gets wet from rain, bubbles will form, which severely affects its adhesion as well as other physical and mechanical properties and corrosion resistance. Therefore, when carrying out painting work, it is necessary to take into account the effects of season and weather and implement appropriate measures; sometimes it is also required to make suitable adjustments to the paint formula, especially for polyurethane paints and similar products. In winter, the amount of curing agent should be increased to 0.1%, while in summer it should be reduced to 0.03%. Otherwise, if the amount used is too low, the curing time to form a film is too long, which affects the performance of the coating film and hinderes automated processing. If too much is used, the viscosity of the coating increases too rapidly, resulting in a short service life and making application difficult; in severe cases, the coating may even gel and become unusable. Bubbles can also form in the resulting coating film, severely compromising its decorative and protective properties.