A reclosable bag that can be hermetically sealed. The bag comprises a pair of zipper strips that are joined in respective zones without substantial deformation of the longitudinal profiled closure elements. These zones of zipper strip joinder assist in providing a leakproof transition from the openable section of the zipper to the corner seals, where the longitudinal profiled closure elements are either substantially deformed (e.g., crushed) or absent. The method of manufacture involves the steps of ultrasonically welding a wide area and then thermally crushing a narrower area overlapping the wide welded area to form leakproof zipper joints. This method can be applied to string (flangeless) zippers as well as flanged zippers.