AbstractMany cured, black‐loaded rubbers contain varying amounts of inorganic fillers: to characterize the rubber, absorptions due to fillers must be recognized and identified. Reference spectra of all the common inorganic fillers used in the rubber industry have been recorded and their recognition in infrared spectra of ultra‐thin microtomed sections of known and unknown samples is described. Both rubbers and inorganic fillers can usually be identified in cured samp