A method of non-destructively determining the amount of ultraviolet degradation of a surface and/or paint adhesion characteristics of the surface corresponding with UV damage including determining a physical property of a composite material/surfacing film by providing a series of composite materials/surfacing films which are subjected to increasing UV light exposure to create a set of UV damage standards, collecting mid-IR spectra on those standards, performing data pre-processing and then multivariate calibration on the spectra of the composite materials/surfacing films, and using that calibration to predict the UV damage for samples in question.