a process for preparing a thermoplastic container including the steps of providing a biaxially oriented , crystallized precontainer having a first contained volume , and further crystallizing the precontainer by applying heat thereto while the precontainer is substantially unconstrained , and forming a deformed precontainer having a second contained volume . deformation of the precontainer is controlled by controllably closing the precontainer prior to further crystallizing and while the precontainer remains substantially unconstrained to create a predetermined increased air pressure therein , and reshaping the deformed precontainer into a final container shape .