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The rate at which the optical properties of liquid crystals respond to the changes in the surface temperature is an important parameter for transient experiments. The time taken for any point within the liquid crystal layer to achieve the heated surface temperature is a function of the distance from the surface, the layer thickness and the film diffusivity. Ireland and Jones (1987) measured the response of TLC material and showed that the delay between the time at which the thin aluminum foil reached the steady-state color display temperature and the occurrence of the color display was no more than a few milliseconds (around 3 ms). Moffat (1990) suggested that the molecular reorientation time of LCs after reaching a steady state temperature is of the order of 5-10 ms for chiral nematics and 50-100 ms for cholestrics. Kobayashi (1998) numerically simulated the thermal response of an individual encapsulated particle by considering both the chiral nematic LC core and the gelatin encapsulation properties and calculated the response time to be as much as 150 ms. Given these numbers, it is clear that transients that last a few minutes onwards to a few hours will be comfortably time-resolved by liquid crystal thermography. Special treatment would be required if the characteristic timescales are a few hundred milliseconds or smaller.