On the basis of a numerical solution of the problem for nonisothermal compaction and cooling of viscous compressible materials within a cylindrical chamber the effect of thermal factors and specimen geometrical dimensions on the characteristic times for two autonomous processes is analyzed: spatial propagation of a compression zone through a specimen from layer to layer and temporary additional compaction of material within the compression zone itself. It was revealed that the effect of retarding compaction (induction period) increases with distance of a specimen cross section from the moving piston as conditions for thermal insulation of the specimen ends worsen. The previously known experimental result of two critical specimen dimensions that govern conditions for preparing pore-free materials is confirmed and substantiated.