[en] Sintering in compacted powders of Mo, Nb, Ta, and alumina is investigated using small angle neutron scattering. The scattering data permits to follow the evolution of the total pore surface F together with the total pore volume V in the course of the entire densification process. Characteristic changes in the relation between F and V suggest that sintering proceeds in three different stages. Quantitative evidence is presented that, in particular, third stage sintering (taking place if the pores can be considered isolated from each other) is governed by a universal relation between F and V