Abstract: Process for forming containers from a blank, preferably a preform, made of a thermoplastic, the containers being formed using a stretch-blow moulding machine of rotary type having a blow-moulding mould mounted on the periphery of a carousel rotated continuously about its axis, the blow-moulding mould operating in cyclic manner according to a blow-moulding cycle having the following steps: placing a preheated blank in a blow-moulding mould; closing the blow-moulding mould; blowing the blank in the blow-moulding mould; flushing the inside of the container with a cooling gas, by injecting air thereinto; grasping the blow-moulded container by external gripping means; and opening the blow-moulding mould, which process includes automatically varying the duration of the flushing step at each start of production of the containers, in a temporary and evolving manner for a few minutes to establish in the containers thermal conditions enabling the first containers to be formed at a temperature that gives them a final vo