Corning Museum of Glass

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.

The technique of forming a vessel by winding or gathering molten glass around a core supported by a rod. After forming, the object is removed from the rod and annealed. After annealing, the core is removed by scraping.

A small, heavy object designed to hold down loose papers. The first glass paperweights were made in the early 1840s in Venice and France, and their manufacture spread rapidly to other parts of Europe and the United States. Glass paperweights ceased to be fashionable in the early 20th century, but the craft of making them revived in the 1950s.

A tool with two metal arms joined at one end by a spring. The distance between the arms is controlled by the glassworker, who uses jacks for a variety of purposes while shaping the parison (for example, to form the mouths of open vessels). This tool is also known as a borsella or pucellas.

An iron or steel tube, usually four to five feet long, for blowing glass. Blowpipes have a mouthpiece at one end and are usually fitted at the other end with a metal ring that helps to retain the gather.

(Noun) A mass of molten glass (sometimes called a gob) collected on the end of a blowpipe, pontil, or gathering iron; (verb) to collect molten glass on the end of a tool.

A vitreous substance made of finely powdered glass colored with metallic oxide and suspended in an oily medium for ease of application with a brush. The medium burns away during firing in a low-temperature muffle kiln (about 965°-1300°F or 500°-700°C). Sometimes, several firings are required to fuse the different colors of an elaborately enameled object.

(French, “glass paste”) A material produced by grinding glass into a fine powder, adding a binder to create a paste, and adding a fluxing medium to facilitate melting. The paste is brushed or tamped into a mold, dried, and fused by firing. After annealing, the object is removed from the mold and finished.

Any crystalline inclusion present in glass. Stones consist of unmelted particles of batch, fragments of refractory material from the pot, or devitrification crystals. Stones of the first two varieties are generally irregular but rounded; those of the third variety are angular and well formed.

These terms and their French and Italian equivalents, pâte de verre and pasta vitrea, have been used since at least the 17th century to describe the composition of small objects such as medallions and imitations of precious stones. However, their use to describe such objects is incorrect (they were made with molten glass, sometimes with a high lead content), and they should be restricted to objects of pâte de verre, as described in the next entry.

These terms and their French and Italian equivalents, pâte de verre and pasta vitrea, have been used since at least the 17th century to describe the composition of small objects such as medallions and imitations of precious stones. However, their use to describe such objects is incorrect (they were made with molten glass, sometimes with a high lead content), and they should be restricted to objects of pâte de verre, as described in the next entry.

The process of slowly cooling a completed object in an auxiliary part of the glass furnace, or in a separate furnace. This is an integral part of glassmaking because if a hot glass object is allowed to cool too quickly, it will be highly strained by the time it reaches room temperature; indeed, it may break, either as it cools or at some later date. Highly strained glasses break easily if subjected to mechanical or thermal shock.

The technique of removing the surface of an object with a rotating wheel fed with an abrasive, or by some other means.

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).

(1) The process of founding or melting the batch; (2) heating pieces of glass in a kiln or furnace until they bond (see Casting and Kiln forming); (3) heating enameled glasses until the enamel bonds with the surface of the object.

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.

A separate ring of glass added to the base after the body of the vessel has been formed.

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 type of Art Glass made by several American factories in the late 19th century. It resembled the peach bloom glaze on 17thto 18th-century Chinese porcelain such as the celebrated Morgan Vase. Most Peachblow glass had a surface that shaded from opaque cream to pink or red, sometimes over opaque white. Similar glass was made in England by Thomas Webb & Sons and Stevens & Williams.

(1) Several types of glass with newly developed surface textures, shaded colors, or casing, made in the United States from about 1870 and in Europe between about 1880 and 1900; (2) more generally, especially when written “art glass,” any ornamental glassware made since the mid-19th century.

An air-filled void, which may be of almost any shape. Air traps in stems are frequently tearshaped or elongated and spirally twisted.

A component, usually bulbous, of the stem of a drinking glass, hollow or solid, used either singly or in groups, and placed contiguously or with intermediate spacing; also the finial at the center of a lid.

(from French paraison) A gather, on the end of a blowpipe, that is already partly inflated.

(from French marbre, “marble”) (Noun) A smooth, flat surface on which softened glass is rolled, when attached to a blowpipe or pontil, in order to smooth it or to consolidate applied decoration. (Verb) To roll softened glass on a marver.

(from Greek phiale, “bowl” or “pan”) A broad, flat bowl for drinking or pouring libations.

(1) A rounded, hollow vessel; (2) the uppermost part of a goblet, tazza, or wineglass.

An ancient Roman vessel decorated with a continuous band of vertical ribs.

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.

A cylindrical or truncated conical one-piece mold with a patterned interior. The mold is open at the top so that a parison can be dipped into it and then inflated. It is also known as an optic mold.

Susceptible to being modeled or shaped. When it is in a molten state, glass can be described as plastic.

Smoothing the surface of an object when it is cold by holding it against a rotating wheel fed with a fine abrasive such as pumice or cerium oxide. Glass can also be polished with hand-held tools.

The application of a layer of glass over a layer of contrasting color. The gaffer either gathers one layer over another gather, or inflates a gob of hot glass inside a preformed blank of another color. The two components adhere and are inflated together (perhaps with frequent reheating) until they have the desired form. Sometimes, the upper layer is carved, cut, or acid-etched to produce cameo glass.

A drinking vessel with a bowl that rests on a stemmed foot.

The pontil, or punty, is a solid metal rod that is usually tipped with a wad of hot glass, then applied to the base of a vessel to hold it during manufacture. It often leaves an irregular or ring-shaped scar on the base when removed. This is called the “pontil mark.”

The pontil, or punty, is a solid metal rod that is usually tipped with a wad of hot glass, then applied to the base of a vessel to hold it during manufacture. It often leaves an irregular or ring-shaped scar on the base when removed. This is called the “pontil mark.”

The pontil, or punty, is a solid metal rod that is usually tipped with a wad of hot glass, then applied to the base of a vessel to hold it during manufacture. It often leaves an irregular or ring-shaped scar on the base when removed. This is called the “pontil mark.”

A monochrome segment of glass cut from a trail.

A thin, monochrome rod, or a composite rod consisting of groups of rods of different colors, which are bundled together and fused to form a polychrome design that is visible when seen in cross section.

The mixture of raw materials (often silica, soda or potash, and lime) that is melted in a pot or tank to make glass. Cullet, as well as minor ingredients such as colorants, can be added to the batch to help the melting process.

A fire-clay container in which batch is fused and kept molten. The glassworker gathers glass directly from the pot.

In glassmaking, a soluble salt consisting mainly of potassium carbonate or sodium carbonate. It is one of the essential ingredients of glass, generally accounting for about 15-20 percent of the batch. The alkali is a flux, which reduces the melting point of the major constituent of glass, silica.

Sodium carbonate. Soda (or alternatively potash) is commonly used as the alkali ingredient of glass. It serves as a flux to reduce the fusion point of the silica when the batch is melted.

A form of glass containing three major compounds in varying proportions: silica (usually about 60-75 percent), potash (12-18 percent), and lime (5-12 percent). Forest glass is a common type of potassium-lime glass. Potash glass is slightly denser than soda-lime glass; it passes from the molten to the rigid state more quickly, and it is therefore more difficult to manipulate into elaborate forms. However, it is harder and more brilliant, and it lends itself to decorative techniques such as facet cutting and copperwheel engraving.

Historically, the most common form of glass. It contains three major compounds in varying proportions, but usually silica (about 60-75 percent), soda (12-18 percent), and lime (5-12 percent). Soda-lime glasses are relatively light, and upon heating, they remain plastic and workable over a wide range of temperatures. They lend themselves, therefore, to elaborate manipulative techniques.

Glass made in the rural glasshouses of central and northern Europe in the late Middle Ages and the early modern period. Most forest glass was fluxed with potash derived from the wood with which the furnaces were fueled. It is green because of iron impurities in the sand from which it was made. The German term for forest glass is Waldglas.

The process of cutting into the surface of an annealed glass object either by holding it against a rotating copper wheel fed with an abrasive or by scratching it, usually with a diamond.

The technique whereby glass is removed from the surface of an object by grinding it with rotating wheels made of stone, wood, and cork. The first stage of the process employs a stone wheel under a continuous stream of water. Later, wheels of fine-grained stone and wood, fed with various abrasives, are used to grind and polish the surface.

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

Potassium carbonate. It is an alternative to soda as a source of alkali in the manufacture of glass.

Calcined limestone, which, added to batch in small quantities, gives stability. Before the 17th century, when its beneficial effects became known, lime was introduced fortuitously as an impurity in the raw materials. The addition of insufficient lime can cause crizzling.

Forcing hot glass into an open or multipart mold by means of a plunger.

A tool with two metal arms joined at one end by a spring. The distance between the arms is controlled by the glassworker, who uses jacks for a variety of purposes while shaping the parison (for example, to form the mouths of open vessels). This tool is also known as a borsella or pucellas.

A tool with two metal arms joined at one end by a spring. The distance between the arms is controlled by the glassworker, who uses jacks for a variety of purposes while shaping the parison (for example, to form the mouths of open vessels). This tool is also known as a borsella or pucellas.

(Italian, from the dialect word pulega, “bubble”) Glass containing numerous bubbles of all sizes, produced by adding bicarbonate of soda, gasoline, or other substances to the melt. The bubbles make the glass semiopaque and give the surface an irregular texture. Pulegoso was developed by Napoleone Martinuzzi (1892-1977) on the island of Murano, Italy, in the 1920s.

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.

The fluid glass produced by melting batch.

The process of pulling semimolten glass to elongate it. It is used, for example, in the production of canes.

Glass in which the flux is boric oxide instead of alkali. The first %%borosilicate glass%% was created by Otto Schott in 1882. It has a low coefficient of expansion and therefore withstands sudden changes of temperature.

The technique of forming objects from rods and tubes of glass that, when heated in a flame, become soft and can be manipulated into the desired shape. Formerly, the source of the flame was an oil or paraffin lamp used in conjunction with foot-powered bellows; today, gas-fueled torches are used.

A type of borosilicate glass perfected in 1915 by W. C. Taylor and Eugene Sullivan of Corning Glass Works in Corning, New York. Pyrex rods can be used in flameworking.

(from Greek and Latin), pl. pyxides. A covered box for the toilet table, used to contain cosmetics, medicines, and jewelry.

(from Greek and Latin), pl. pyxides. A covered box for the toilet table, used to contain cosmetics, medicines, and jewelry.