Bulk moulding compound (BMC) composites have been cured in heated moulds, following an irreversible reaction which transforms the polymer into a three-dimensional network. The process is very complex because conduction heat transfer is associated with the heat evolved from the cure reaction. Modelling of this process is necessary, enabling simulation of the process and thus providing more information than experiments. The deconvolution of the two phenomena, heat transfer and chemical reaction, allows one to understand better the evolution of the process and to optimize the operational conditions. The contributions to the rise in temperature from heat conduction and chemical reaction have different histories in different parts of the composite, and can explain the temperature-, state-of-cure-, or heat-flux-time histories. The reaction-rate-time history is very sensitive in the earlier stages of curing, and supplements information obtained from the state-of-cure histories. The study was made on a thin sheet of composite in a metallic mould heated by oil, with one-dimensional heat transfer. The analysis was made using a numerical method that has been previously described and tested.