It is the film's ability to retain liquids such as paints, inks and adhesives. It is measured in dynes / cm. To have a sufficient level of wettability, polypropylene (BOPP) is subjected to corona treatment (the surface of the film is exposed to a strong difference in electrical potential which induces the formation of polar groups on the outermost part of the film). On the other hand, polyester (PET), due to the chemical nature of its monomer, already has a high level of wettability which can in any case be increased by applying the corona treatment. Another way to increase the ability to hold liquids is to apply an acrylic coating to the film. In this way, the chemical affinity between the film and the deposited material increases.