Test inks are used to determine the wettability and thus the surface energy of a surface. If the surface has a surface energy of approx. 38 mN/m or higher, printing, lacquering or gluing is typically possible. Therefore, it is often necessary to determine the surface energy with the help of test inks before this process. The test ink is applied to the substrate with a brush and the behaviour is observed. If the test ink contracts, the wettability of the substrate is lower than the indicated surface energy value of the test ink. However, if the ink remains on the substrate, the surface energy of the material is as high or higher than that of the ink.
In order to increase the surface energy, the substrate is treated with plasma prior to the respective process.