Glassmaker's jacks
Glassmaker's jacks are a tool with two metal arms joined by a spring at one end. The glassworker controls the distance between the arms to shape the hot glass blank, including the mouths of open vessels.
Names and use
Corning Museum of Glass also records the names borsella and pucellas. Jacks belong to hot-glass forming. They are distinct from glazier's pliers used for working cold sheet glass, and from shears used to trim surplus hot glass.
Recording an older tool
Document arm length and profile, spring connection, grip and any marks. Examine working surfaces for modification or later repairs. A plier-like outline alone is not secure identification. Workshop provenance and comparison with documented glassmaking tools provide stronger evidence. Wear does not prove association with a particular Norwegian glassworks.
