Thermomechanical indentation is a unique technique which tests the mechanical properties of a polymer film. Its key principle is the kinetic analysis of the relaxation response of a polymer upon mechanical indentation. If being combined with a dedicated heating step above a material-specific threshold temperature at which only the cross-linked fraction of a cross-linking polymer remains rigid, this method can be used to determine the degree of cross-linking for polymers like ethylene vinyl acetate (EVA) or polyolefin (POE) which are frequently used as encapsulants in photovoltaic modules. Here, the degree of cross-linking is an important measure for the quality of the module encapsulation. As the mechanical response of a polymer (stack) depends on its actual properties, thermomechanical indentation measurements do not constitute an absolute measurement method but either rely on the (one-time) calibration with an absolute method like Soxhlet extraction or on the use with known and consistent bills of materials, in which case the measured quantity, the so-called LXM value (LayTec X-Linking Metric) is self-consistent and can be used as a specification parameter.