Fast firing has been used to produce relatively dense ceramics in periods of time shorter than 5 min. High heat inputs during fast firing originates changes in the internal structure of the ceramic compact. The amount of energy available for sintering increases by the formation of a dense outer layer which controls the heat flux to the interior of the compact. In this paper, a numerical model based on the method of finite volumes was developed to simulate the fast firing process in an alumina compact. The heat transfer inside the ceramic sample was modeled through the whole process in order to predict the density changes induced by the fast furnace's heat transfer and compared to conventional sintering.