Among the most ancient of glassmaking techniques, core forming was used in the fabrication of small stoppered bottles, of the alabastron type, for storing precious ointments and perfumes.

Core forming was practiced for many years, from the XVIth to the Ist century BCE, in Mesopotamia, Western Asia and through the Mediterranean world. The artisan would first shape a core of clay and dung to define the interior dimensions of the vessel. After inserting a metal shaft into the core, the unit would then be left to dry. Next, the artisan would dip the core into a crucible of molten glass while carefully turning the shaft to ensure an even distribution of material. Necks and handles were shaped with hand tools or applied hot. A typical decoration was often made using hot threads applied in a spiral around the vessel, reheated to fuse completely with the piece, and sometimes combed into wavelets. After cooling, the metal shaft could be removed and the core pulverized. This archaic technique has fallen into obsolescence since the invention of the blow pipe.