Fire investigation is a challenging area for the forensic investigator. The aim of this work was to use spectral changes to paint samples to estimate the temperatures to which a paint has been heated. Five paint samples (one clay paint, two car paints, one metallic paint, and one matt emulsion) have been fully characterized by a combination of attenuated total reflectance Fourier transform infrared (ATR-IR), Raman, X-ray fluorescence spectroscopy and powder X-ray diffraction. The thermal decomposition of these paints has been investigated by means of ATR-IR and thermal gravimetric analysis. Clear temperature markers are observed in the ATR-IR spectra namely: loss of v(C = O) band, greater than 300 degrees C; appearance of water bands on cooling, greater than 500 degrees C; alterations to v(Si-O) bands due to dehydration of silicate clays, greater than700 degrees C; diminution of v(CO3) and o(CO3) modes of CaCO3, greater than 950 degrees C. The researchers suggest the possible use of portable ATR-IR for nondestructive, in situ analysis of paints. Abstract published by arrangement with John Wiley & Sons.