Making Glass
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How a core-formed vessel is made
(Image courtesy of Lynn Swartz Dodd*)
The vessels were formed around a disposable core made of clay or sand mixed together with an organic binder which was then covered with molten glass. Colored threads of soft glass were wound around the vessels, and a pointed instrument was dragged across the threads to create the charming zigzag and stripe patterns that characterize such works. Core-formed vessels were exported widely across the Mediterranean world. (Grose 1989: 31*)
Throughout the process of creation (in order to create handles, base-knobs, etc. that are added once the body is made) the vessel is constantly under the process of being reheated. The disposable core, which is around a metal rod, is left inside, while the rod is taken out. As soon as the vessel has hardened, the core is scraped out. (Grose 1989: 31*)