a method for forming a plastic container in which a heated end product is introduced into a heated preform to expand the preform into at least partial conform with the cavity surfaces of a mold , thereby forming a resultant container , of a first size , with a heated end product . the resultant container is then capped and shrunk to a second size , which is less than the first size . the shrinkage of the reluctant container is greater than the shrinkage of the end product thereby creating a positive pressure within the capped container .