Recent studies of the thermal histories of archaeological materials with electron spin resonance (ESR) spectroscopy have been extended to black materials encountered in archaeology and in the conservation of antiquities. The ESR parameters of jet. charcoal and lampblacks are reported and comparisons made with a range of related materials Discrimination and characterization is achieved by simultaneous consideration of the three main parameters of the ESR signal due to radical carbon. This study is the first attempt using ESR spectroscopy to discriminate between jet and related coal‐like substance