By about AD 20, Roman workers had discovered that a bubble of molten glass could be lowered into a mold and then further inflated to fill the mold. In this way, the full-size vessel, complete with elaborate decoration, was made almost instantly.
A pocket of gas trapped in glass during manufacture. The term is used both for bubbles introduced intentionally (known as air traps or beads) and for unwanted bubbles created during the melting process. Very small bubbles are known as seeds.
A form used for shaping and/ or decorating molten glass. Some molds (e.g., dip molds) impart a pattern to the parison, which is then withdrawn, and blown and tooled to the desired shape and size; other molds (sometimes known as full-size molds) are used to give the object its final form, with or without decoration. Dip molds consist of a single part and are usually shaped like beakers. Full-size molds usually have two or more parts and can be opened to extract the object. Nowadays, most molds are made of metal, but stone, wood, plaster, and earthenware molds were used in the past and are still occasionally employed today.