A tool used to trim excess hot glass from an object in the course of production. Many modern shears are embedded with chips of industrial diamonds.

Any instrument used by glassworkers to develop and shape an object. Glassworkers’ tools include the blowpipe, pontil, gathering iron, jacks, shears, clapper, pallet, block, pincers, battledore, lipper, and crimper.

Inflating a parison of hot glass in a mold. The glass is forced against the inner surfaces of the mold and assumes its shape, together with any decoration that it bears.

The technique of forming an object by inflating a gather or gob of molten glass on the end of a blowpipe. Traditionally and in modern furnace working, the gaffer blows through the tube, slightly inflating the gob, which is then manipulated into the required form by swinging it, rolling it on a marver, or shaping it with tools or in a mold. It is then inflated to the desired size. In flameworking, one end of the glass tube is heated and closed immediately, after which the worker blows into the other end and manipulates the hot glass.

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 Some molds (e.g., dip molds) impart a pattern to the parison, which is then withdrawn, and blown and tooled to the desired shape and size; other molds (sometimes known as full-size molds) are used to give the object its final form, with or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.

Silicon dioxide, a mineral that is the main ingredient of glass. The most common form of silica used in glassmaking has always been sand.

The most common form of silica used in making glass. It is collected from the seashore or, preferably, from deposits that have fewer impurities. For most present-day glassmaking, sand must have a low iron content. Before being used in a batch, it is thoroughly washed, heated to remove carbonaceous matter, and screened to obtain uniformly small grains.

The process of (1) heating the batch in order to fuse it into glass by exposing it to the required temperature in a crucible or pot, (2) reheating unfinished glassware while it is being worked, or (3) reheating glassware in a muffle to fuse enamel or gilding. The melting of the batch may require a temperature of about 2400°-2750°F (1300°-1500°C), whereas the muffle kiln may require a temperature of only about 950°- 1300°F (500°-700°C).

A type of 19th-century glassware with an allover silver appearance, made by applying a solution of silver nitrate between the walls of a double-walled vessel. The solution was introduced through a hole in the base, which was then sealed to prevent the silver from oxidizing. Silvered glass is sometimes known, mistakenly, as “mercury glass.” The technique was patented in England by Edward Varnish and F. H. Thompson in 1849, and in America by William Leighton in 1855.

(German, “gold between glass”) A type of decoration, produced in Bohemia and Austria in the 18th century, in which a design in gold or silver leaf is incorporated between two vessels that fit together precisely. Unlike Hellenistic and Roman gold glass, which is fused, Zwischengoldglas is bonded with cement.

Its many meanings include an emblem impressed on wax or some other plastic substance as evidence of ownership or authenticity. Since the 17th century, many bottles have borne stamped glass seals that identify the producer of the contents, the tavern in which they were used, or the individual for whom the contents were bottled.

Batch ingredients such as sand and alkali, which have been partly reacted by heating but not completely melted. After cooling, frit is ground to a powder and melted. Fritting (or sintering) is the process of making frit.