A method for manufacturing plastic containers in which, for each container, a plastic preform containing air is supplied; the preform is heated at a preform temperature over the glass temperature of the preform material, the preform is inserted in a mold having a mold cavity; and the preform is expanded to a container having the shape of a mold cavity by a forming liquid. The method also includes, between steps (b) and (d), the injecting of a gaseous product into the preform containing air, wherein the gaseous product is absorbable by the forming liquid. The injection conditions of the gaseous product are selected such that the injected gaseous product expels the air out of the preform.