Posted 1 Aug 2022

The best temperature and humidity during the painting process

It is difficult to determine the optimum temperature and humidity during the painting process, as there are many factors to ponder. Generally speaking, the temperature inside a spray booth can be considered ideal between +19°C and +24°C, and relative humidity between 40% and 60%. Still, in practice, we must also be aware of the type of paint, the hardeners (if any), the surface to be treated, the way the product is applied, and, last but not least, the season or the climate during which the painting process takes place. 

The ideal temperature in a spray booth

The ideal temperature in a spray booth must be checked very carefully before starting any operation. In fact, a temperature that is too low or too high would change the humidity of the air, the surfaces to be painted and the required product, causing one of the most common paint defects, such as orange peel.

The critical thing to know is that not only the temperature inside the booth must be within the recommended range for that type of application, but so must the substrate, whatever the material, and the required product for that application. 

Another inevitable consequence of an incorrect temperature during the painting process is a change in drying times, often resulting in higher energy costs for the body shop.

The ideal humidity in a spray booth

The humidity in a spray booth can also make a difference in the final result. In brief, if the humidity is too high, it can cause the formation of small pockets of liquid, which, after drying, may result in craters and other paint defects. On the other hand, if the humidity is too low, this may lead to reduced fluidity of the atomized paint and covering capacity, with halos or stains on the painted surfaces.

The problem with measuring the humidity in the spray booth is that it is very much affected by the climatic conditions outside the paint facility. In winter, with low temperatures, there is less humidity in the air (despite our personal perception of “humidity”), while in summer, with high temperatures, the humidity in the air can vary considerably from place to place. An aspect that is always worth remembering. For this reason, Air Handling Units are essential for bringing the air humidity value to the optimal working threshold.

Paint temperature and humidity according to the substrate material and intended use

Lastly, temperature and humidity must also consider the material and intended use of the substrate to be treated. For instance, steel and aluminum, plastics and composites, or wood require different humidity and temperature levels precisely because of their different response to heat and moisture variations. Similarly, particular applications such as aeronautics, nautical, or Formula 1, where almost every drop of paint can make a difference in terms of performance or fuel consumption, require specific conditions that also affect the air inside the spray booth. As a result, paints and finishes are becoming increasingly specific, and, in order to reduce consumption and save energy, they also require specific conditions for the air inside the booths. 

Thanks to USI Italia’s EPS 2.0 and complementary products such as the Air Handling Unit and the Evaporative Cooling Humidification Kit, with USI Italia painting systems it is possible to set and control air temperature and humidity in a smart way and in real-time with significant energy savings.

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