Infrared curing of polymer films on metallic substrates presents a number of concerns related to specular reflectance. This phenomenon is studied by simulating the infrared specular reflectance spectrum of poly(methylmethacrylate), PMMA coated on an aluminum substrate. The simulation involves obtaining the complex refractive index of PMMA, and using Maxwell's equations to determine specular reflectance spectra as a function of angle of incidence and film thickness. The results show that there is an anomalous loss of light absorption in thin films on metallic substrates, and that the absorption oscillates as the film thickness increases. Both of these effects are a direct consequence of the electric field associated with the infrared light vanishing to zero at the surface of the metal.