The burning rates of a slow reacting Mn+Sb2O3 and a fast reacting Si+Pb3O4 time delay composition, filled into lead tubes, were measured with an infrared camera, with two thermocouples and in the form of a fully assembled detonator. The infrared camera method returned values that were on average about 12% lower than those recorded for the detonators. The temperature profiles measured for the slow burning elements were fully developed, whereas those obtained for the fast burning Si+Pb3O4 elements were not. A numerical model was developed to simulate the Mn+Sb2O3 system. Kinetic parameters were determined by least square fits to the recorded surface temperature profiles. The model made it possible to determine the effect of various property variations on the burning rate. The thermal conductivity of the delay composition was found to have the smallest impact and the heat of reaction the largest effect.