A comestible gelatin capsule 10 for holding a substance in hermetic isolation includes a capsule body 12, a diaphragm 14 located within the capsule body and an end cap 16. Overlapping open end regions of walls 22 and 28 of the capsule body 12 and of the diaphragm 14, respectively, are fused to one another in a fusion welding process wherein the end regions undergo partial phase change so as to form a circumferential fused homogeneous sealing zone 36. The overlapping end regions are bent inwardly in the fusion welding process such that a portion of the wall 22 extends inwardly across a portion of the wall 28 thereby restricting axial movement of the capsule body and the diaphragm relative to one another forming a stable robust and effective hermetic seal.