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1.1 This International Standard specifies a method for determining the wetting tension of surfaces of plastic film and sheeting in contact with drops of specific test solutions. 1.2 The ability of plastic films to retain inks, coatings, adhesives, etc., is primarily dependent on the character of their surfaces, and can be improved by one of several surface-treatment techniques. These same treatment techniques have been found to increase the wetting tension of a plastic film surface in contact with mixtures of solvents. It is therefore possible to relate the wetting tension of a plastic film surface to its ability to accept and retain inks, coatings, adhesives, etc. The measured wetting tension of a specific film surface can only be related to acceptable ink, coating, or adhesive retention through experience. Wetting tension, in itself, is not a completely acceptable measure of ink, coating or adhesive adhesion. 1.3 Any contamination of the film surface and any trace of surface-active impurities in the liquid reagents may affect the wetting tension. It is therefore important that the portion of the film surface to be tested is not touched or rubbed, that all equipment be scrupulously clean, and that reagent purity be carefully controlled. Glass apparatus, in particular, is likely to be contaminated with detergents having very strong surface tension reducing ability, unless specific precautions are taken to ensure their absence such as by cleaning with an oxidizing agent, for example chromic-sulfuric acid or sulfuric acid-ammonium peroxydisulfate, and rinsing with distilled water. 1.4 The test is not applicable when the surface of the material to be tested reacts chemically with the test solution. 1.5 It should be noted that surface properties of plastic film and sheeting may change by ageing processes. The measurements must therefore be related to the age of the film.