Test inks are used to determine the wettability, the surface energy or surface tension, of a surface. If the surface has a surface energy of approx. 38 mN/m or higher, printing, varnishing or bonding is well possible. Therefore, the surface energy must often be determined with the aid of test inks prior to this process. The test ink is applied to the substrate with a brush and the behavior is observed. If the ink contracts, the wettability of the substrate is lower than that of the ink. However, if the ink remains on the substrate, the surface energy of the material is equal to or greater than that of the ink. Plasma pretreatment of the substrates can significantly increase the surface energy, as a test shows:
In order to increase the surface energy, the substrate is treated with plasma prior to the respective process.