Also surfaces which are clean to the eye are often covered with fine grease or oil films. This can be due to a variety of causes: release agents from a preceding production process, exudation of additives such as drag reducers, contact with oil mists during storage, or simply touching with hands and fingers. Even very thin layers of grease prevent perfect gluing, printing or coating. Also ultra-small grease and oil residues can be removed in a plasma cleaning process, in low-pressure as well as in atmospheric pressure plasma. Plasma cleaning also degreases narrow cracks and hollows.