Corning Museum of Glass

The technique of decorating glass in high relief by cutting or carving away part of the glass between the body of an object and its decoration (e.g., on a cage cup).

An ancient Roman vessel decorated by undercutting so that the surface decoration stands free of the body of the glass, supported by struts. The vessel appears, therefore, to be enclosed in an openwork cage. Cage cups are sometimes known as diatreta or vasa diatreta.

A term used by Frederick Carder (1863-1963) to describe openwork objects that he made by lost wax casting.

Work that is perforated. Openwork in glass objects can be made by creating a network of trails, by casting (see Diatreta), or by cutting (see Cage cup).

(Italian, “chalcedony”) Glass marbled with brown, blue, green, and yellow swirls in imitation of chalcedony and other banded semiprecious stones. Calcedonio was first made in Venice in the late 15th century.

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.

Glass of one color covered, usually by casing, with one or more layers of contrasting color(s). The outer layers are acid-etched, carved, cut, or engraved to produce a design that stands out from the background. The first cameo glasses were made by the ancient Romans. The genre was revived in England and, to a lesser extent, in America in the late 19th century.

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 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.

The removal of glass from the surface of an object by means of hand-held tools or sandblasting.

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.

(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 monochrome segment of glass cut from a trail.

A drinking vessel with a bell-shaped body, a foot, and two handles. Kantharos (from Greek), cantharus (from Latin)

A drinking vessel with a bell-shaped body, a foot, and two handles. Kantharos (from Greek), cantharus (from Latin)

Glassware formed by placing a blob of molten glass in a metal mold and pressing it with a metal plunger or “follower” to form the inside shape. The resultant piece, termed “mold-pressed,” has an interior form independent of the exterior, in contrast to mold-blown glass, whose interior corresponds to the outer form. The process of pressing glass was first mechanized in the United States between 1820 and 1830.

The rainbowlike effect that changes according to the angle from which it is viewed or the angle of incidence of the source of light. On ancient glass, iridescence is caused by interference effects of light reflected from several layers of weathering products. On certain 19th- and 20th-century glasses, iridescence is a deliberate effect achieved by the introduction of metallic substances into the batch or by spraying the surface with stannous chloride or lead chloride and reheating it in a reducing atmosphere.

The process of removing glass or imparting a matte finish by bombardment with fine grains of sand that are propelled by compressed air.

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.

(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.

(corruption of “grandfather”) The master craftsman in charge of a chair, or team, of hot-glass workers.

Any cooled glass object that requires further forming or decoration to be finished.

A mass of molten glass, usually small and freshly gathered from the furnace. In a team of glassworkers, the bit gatherer removes bits from the furnace, using a bit iron. Bits are also known as gobs.

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 group of matching vessels, usually with a tray or rack, that includes containers for salt, pepper, and mustard, and perhaps also cruets for oil and vinegar.

A small vessel with a perforated top from which one casts or sprinkles sugar or condiments such as pepper. A castor set is a matching group of castors, which, together with cruets, form a condiment set.

A small, ewerlike vessel, usually with a lip or spout, a handle, and a stopper, for serving condiments at the table.

The generic name for a wide variety of techniques used to form glass in a mold.

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.

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

(1) The bench used by the gaffer while forming a glass object. Traditionally, this is a wide bench with arms, on which the gaffer rests the blowpipe with its parison of molten glass and rolls it backward and forward so that the parison retains its symmetrical shape during the forming process. (2) The team of glassworkers who assist a gaffer.

A colorless glass containing chalk, developed in Bohemia in the late 17th century. Vessels of thick chalk glass were often elaborately engraved.

A stand with a socket or spike for one candle.

(from French, “candlestick”) A lighting fixture suspended from the ceiling, with two or more arms bearing lights (originally, candles) or two or more pendent lights. Many chandeliers have faceted lead glass arms, candle cups, shafts, and prisms, which reflect the light and sparkle like tiny mirrors.

Glass that contains a high percentage of lead oxide (at least 20 percent of the batch). In modern times, glass of this type was patented in 1674 by George Ravenscroft (1632-1683), who added a larger amount of lead in 1676. Lead glass is relatively soft, and its refractive index gives a brilliance that may be exploited by covering the surface with polished wheel-cut facets. Such glass is often known by the term “lead crystal.”

A vessel for cremated human remains. In the Roman period, cremation was a widely used method of disposing of the dead, whose ashes were sometimes placed in glass cinerary urns.

Glass that is colored by (1) impurities in the basic ingredients in the batch or (2) techniques of coloring glass by one of three main processes: (a) using a dissolved metallic oxide to impart a color throughout, (b) forming a dispersion of some substance in a colloidal state, and (c) suspending particles of pigments to form opaque colors.

A type of decorative glass developed by Frederick Carder (1863-1963) at Steuben Glass Works in Corning, New York, before 1917. Most Cintra glass was made by picking up chips of colored glass on the parison and then casing them with a thin layer of (usually) colorless glass.

(1) In the hotshop, the reintroduction of a vessel into the glory hole to melt the surface and eliminate superficial irregularities; (2) in kiln working, exposing the object to significant heat so that it assumes a smooth surface.

The process of etching the surface of glass with hydrofluoric acid. Acid-etched decoration is produced by covering the glass with an acid-resistant substance such as wax, through which the design is scratched. The object is then immersed in hydrofluoric acid, or a mixture of dilute hydrofluoric acid and potassium fluoride is applied to etch the exposed areas of glass. Acid etching was first developed on a commercial scale by Richardson’s of Stourbridge, England, which registered a patent in 1857. An effect superficially similar to weathering can be obtained by exposing glass to fumes of hydrofluoric acid to make an allover matte surface.

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.

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

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 tool consisting of two rectangular pieces of wood joined at one end by a leather hinge. There is an aperture in one of the pieces of wood, and this holds the stem of a goblet or wineglass while it is being made. The clapper is used to squeeze a blob of glass in order to form the foot.

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

The narrow part of a goblet or tazza that separates the bowl and the foot.

A beaker decorated with claw- or trunklike protrusions made by applying blobs of hot glass that melted the parts of the wall to which they were attached. The blobs were then blown outward and manipulated to resemble hollow claws. Claw beakers were made in Europe between the fifth and seventh centuries A.D. Similar decoration was made in Germany in the 16th century.

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 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 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.

(from French aventure, “chance”) Translucent glass with sparkling inclusions of gold, copper, or chromic oxide, first made in Venice in the 15th century. Aventurine glass imitates the mineral of the same name, a variety of translucent quartz spangled with mica or other minerals.

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

(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.

A strand of glass, roughly circular in section, drawn out from a gather.

The technique of decorating an object by applying paint such as artists use on other materials. This is in contrast to enameling, in which powdered glasses of various colors are fused to the surface by heating.

A technique of decorating the surface of an object. Copper disks (wheels) of various sizes and rim profiles are rotated on a spindle. An abrasive such as Carborundum (in the past, emery was frequently used), mixed with oil, is applied to the edge of the wheel. The wheel presses the abrasive against the glass so that it removes the surface by grinding.

A process of decorating the surface of glass by the grinding action of a wheel, using disks of various sizes and materials (usually copper, but sometimes stone), and an abrasive in a grease or slurry applied to a wheel, as the engraver holds the object against the underside of the rotating wheel. See also Cutting and Copper-wheel engraving.

The process of winding a thin trail of glass around an object to create the appearance of parallel lines. In 1876, W. J. Hodgetts of Stourbridge, England, patented a machine that produced very regular and closely spaced threads.

The part of a lamp where the flame is produced.

(1) A band of applied glass around the rim of a vessel. On bottles, the collar is used to secure the cork. (2) A threaded metal ring around the font of a lamp, used to attach a screw-in burner.

The reservoir for oil in a lamp.

The oxide of a metal. Oxides can be used to color glass and enamel, or to produce lustered or iridized surfaces. The resultant color depends primarily on the oxide used, but it can be affected by the composition of the glass itself and the presence or absence of oxygen in the furnace.

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.

(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.

A dish, usually with a stem and a base, and sometimes with a cover, for serving compote (fruits cooked in syrup), or a smaller dish of similar form used for individual servings.

(from French salière, “salt dish”) A small bowl used at the table for salt.

A drinking vessel in the form of an inverted cone. Cone beakers were used in several cultures, including ancient Rome, Sasanian Iran, and early medieval Europe.

A part of the glass that differs in composition from the surrounding matrix. This difference produces a change in the refractive index, which enables the cord to be seen as a streak and so spoils the appearance of the glass.

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.

Objects made from preformed elements placed in a mold and heated until they fuse. The term “mosaic glass” is preferable to “millefiori,” except in the case of Venetian or façon de Venise glass.

A surface decorated with many small, adjoining pieces of varicolored materials, such as stone or glass.

The result of chemical instability in glass caused by an imbalance in the ingredients of the batch, particularly an excess of alkali or a deficiency of stabilizer (usually lime). The instability of the glass results in an attack by atmospheric moisture, which produces a network of cracks in the surface that may feel damp or oily. Crizzling can be slowed or perhaps even halted, but it cannot at present be reversed. Crizzled glass is sometimes described as “sick” or “weeping.”

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.

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.

Quartz (chemically pure silicon dioxide), which is usually colorless. From earliest times, glassmakers sought to imitate it.

(Italian, “crystal”) A term first used in Venice in the 14th century to describe glass that resembles colorless rock crystal. Most Venetian cristallo, however, has a gray or brownish tint.

A popular term for colorless lead glass, which has a high refractive index and consequently is particularly brilliant. In the United Kingdom, glass described as crystal must contain a defined percentage of lead oxide. Today, the word is often used to describe any fine glass tableware.

A glass pane with a pontil mark surrounded by concentric ridges. This was the central part of a large pane of crown glass.

A piece of flat sheet glass used for glazing windows.

The fluid glass produced by melting batch.

A small plate on which users set their tea or coffee cup while drinking from the saucer. Between about 1825 and about 1865, it was fashionable to drink from saucers, and cups were placed on cup plates to avoid staining the tablecloth.

In glassworking, the process of coloring the surface of glass by the application of silver sulfide or silver chloride, which is then fired at a relatively low temperature. The silver imparts a yellow, brownish yellow, or ruby-colored stain, which can be painted, engraved, or etched.

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

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.

The process of reheating a blank until it becomes soft and gradually flows under its own weight over or into a former mold and eventually assumes the shape of the mold. Soda-lime glass becomes soft at about 1110°F (600°C). Slumping is also known as sagging.

A glass cylinder intended to be cut into sheets.