Contact angle measurement is a suitable method for assessing the wettability of joining surfaces. The size of the contact angle thereby depends on the interactions between the joining part and the measuring fluid, whereby the contact angle increases with small interactions. From the determination of the contact angle, the surface energy of the joining parts can also be determined. High surface energies of the materials, which can be achieved on many joined parts only by appropriate surface pretreatment methods, favor the wettability. Due to its flexibility, the contact angle measuring device allows both measurements in the laboratory as well as on site and on horizontal and vertical surfaces. The test liquid is applied manually, and the subsequent evaluation is carried out immediately via a camera integrated into the measuring system.