It is shown that metal films will absorb more infrared radiation if they are madethinner. For most metals, the maximum absorptance is obtained for films which are less than 100 A˚ in thickness. Experiments are reported here for Pt on Si, for which peak absorptance of 3.39‐&mgr;m radiation incident through the Si is found to be 0.5±0.1 for a film 80 A˚ thick.