PWIS stands for Paint Wetting Impairment Substances. The terms covers all problems encountered in the coating of surfaces. On almost all products, whether recently manufactured or from storage, there are – usually invisible – deposits which prevent coats from adhering: greases, oils, silicones, moisture, oxidation layers. By means of plasma cleaning , these deposits can be removed to make surfaces PWIS-free. To check the surfaces after cleaning and before painting, Diener electronic developed a PWIS test set .