We measure the sintering behavior of thin and thick films of ceramics made by stacking several layers of tapes. The stack thickness was varied from 0.12 to 0.50 mm. A powder‐pressed dog‐bone sample, ~1 mm thick served as the baseline. While all specimens exhibit flash sintering, the following differences are noted. (a) The onset of flash, which has been shown to occur within a narrow band of volumetric power density for powder‐pressed dog‐bone shaped specimens, moves to a higher value for the thinner specimens. (b) The power transition collapses, again, to within a narrow band when the power density is normalized with respect to the surface area rather than the volume. (c) Sintering of thinner specimens to full density required a higher current‐density limit. These results point to a deeper significance of black body radiation than its use in estimating the specimen temperature in a steady state of flash that is calculated from the energy balance between electrical and radiated energy. The experiments were carried out on 3 mol% yttria stabilized zirconia at constant heating rate