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Glass Terminology & Facts

Word / Phrase
Definition / Description
Abrasion The technique of grinding shallow decoration with a wheel or some other device. The decorated areas are left unpolished.
Acid Etching 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.
Acid Polishing The process of making a glossy, polished surface by dipping the object, usually of cut glass, into a mixture of hydrofluoric and sulfuric acids. This technique was developed in the late 19th century.
Acid Stamping The process of acid-etching a trademark or signature into glass after it has been annealed, using a device that resembles a rubber stamp to apply the acid.
Aeolipile (from Greek) The name sometimes given to globular or pear-shaped objects with a narrow neck and mouth. The function of these objects is uncertain. The word was originally applied to a device, invented in the second century B.C., in which a closed, water-filled vessel, when heated, was made to rotate by jets of steam issuing from one or more projecting, bent tubes. Most surviving aeolipiles, however, are Islamic; they are believed to be containers.
Air Trap, Air Lock An air-filled void, which may be of almost any shape. Air traps in stems are frequently tearshaped or elongated and spirally twisted.
Alabaster Glass A type of translucent white glass, similar to opal glass, first produced in Bohemia in the 19th century. In the 1920s, Frederick Carder (1863- 1963) introduced alabaster glass at Steuben Glass Works in Corning, New York. Carder’s alabaster glass has an iridescent finish made by spraying the object with stannous chloride and then reheating it.
Ale Glass A type of English drinking glass for ale or beer. Ale glasses, first made in the 17th century, have a tall and conical cup, a stem, and a foot. They may be enameled, engraved, or gilded with representations of hops or barley.
Alembic (from Arabic
al-anbiq, “the still”)
An apparatus used for distilling.
Alkali 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.
Annagelb, Annagrün (German) Two types of glass colored by adding uranium oxide to the batch. Annagelb is yellow, and Annagrün is green. They were developed by Josef Riedel (1816-1894), who named them for his wife, Anna, and they were made from 1834.
Annealer /
Annealing Oven
Oven that is used to cool the glass slowly. The annealer sits at around 900 degrees Farenheight and is brought down to room temperature overnight so that it does not crack under stress.
Amberina A type of Art Glass that varies in color from amber to ruby or purple on the same object. This shaded effect is due to the presence of gold in the batch. The object is amber when it emerges from the lehr, but partial reheating causes the affected portion to become red or purple. Amberina, developed by Joseph Locke (1846-1936) at the New England Glass Company in East Cambridge, Massachusetts, was patented in 1883.
Applied Decoration Heated glass elements (such as canes and trails) applied during manufacture to a glass object that is still hot, and either left in relief or marvered until they are flush with the surface. See also Marquetry and Pick-up decoration.
Art Glass (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.
Assistant The Person (or People) helping the Gaffer make a piece
At-the-Fire The process of reheating a blown glass object at the glory hole during manufacture, to permit further inflation, manipulation with tools, or fire polishing.
Aurene A type of ornamental glass with an iridescent surface made by spraying the glass with stannous chloride or lead chloride and reheating it under controlled atmospheric conditions. Aurene was developed by Frederick Carder (1863-1963) at Steuben Glass Works in Corning, New York, in 1904.
Bar A single piece of glass formed by fusing several canes or rods. A bar can be cut into numerous slices, all with the same design, to be used as inlays or appliqués, or in making mosaic glass.
Barilla (from Spanish) (1) A plant, Salsola soda, which grows extensively on seashores in the western Mediterranean and the Canary Islands; hence (2) an impure alkali made by burning plants of this and related species, formerly used in the manufacture of soap and glass.
Base-Ring See Foot-Ring.
Batch Raw components to be melted into Glass (Silca, Carbon, Lime…) Can be purchased through various manufactureres, however many artists prefer to mix their own batch in order to have greater control over things like purity, color and melting temperatures
Battledore A glassworker’s tool in the form of a square wooden paddle with a handle. Battledores are used to smooth the bottoms of vessels and other objects.
Bench The bench is the center of the hot shoppe. It is where the artist works a piece and is the where all the tools are kept. The bench has two rails spaced on either side going perpendicular to the seat, these rails are used to roll the glass pipes on
Bits 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.
Blank Any cooled glass object that requires further forming or decoration to be finished.
Blobbing The technique of decorating hot glass by dropping onto the surface blobs of molten glass, usually of a different color or colors.
Blowing 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.
Blocks Wood molds that fit in the palm of your hand to be used to shape the glass in the early phases of the process
Blocker The glass worker that actually “blows” the first bubble through the blowpipe and then subsequently transfers that blow-pipe to the Gaffer.
Blowpipe A hollow steel rod, with a mouth piece on one end which the artist blows through to expand a bubble through the hot glass
Borosilicate Glass 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.
Bottle Glass A common, naturally colored, greenish or brownish glass. The color is characteristic of glass that includes traces of iron found in the silica used as the major ingredient. Such glass is inexpensive to produce, and it is used for such items as bottles, when good quality is not essential. Sometimes, additional iron, in the form of iron oxide (or other materials), is employed to darken the color.
Broken-Swirl Ribbing Mold-blown decoration that has two sets of ribs. This is made by blowing the gather in a vertically ribbed dip mold, extracting and twisting it to produce a swirled effect, and then redipping it in the same or another dip mold to create a second set of ribs.
Bubbles Gases in the molten glass while melting in the “pit” get trapped. The hotter the molten glass along with the purity of the quality of the glass can greatly diminish this problem. While gathering the molten glass those bubbles will be transmitted to the actual art piece itself. Some artists do like the bubble effect and use them in their works by forcing a bubble. Installing bubbles may me made with a sharp object being punctured into the molten glass or countless other methods.
Burner Runs the air and gas mixture control for lampworking.
Button A small usually clear amount of molten glass placed on the “working end” of the art piece project to assure proper connection of the glass to the pipe to avoid dropping damage. A button may also be used as a part to the actual glass project to enhance a particular art piece.
(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.
Caliper Tongs that help create and control the molten glass piece.
Cane A cross section of glass made by pulling and stretching molten glass from both ends. Several color pattern and designs can be created. Whatever design is used along with the detail will continue to hold the precise shape, scale all the way down to an invisible dimension.
Carnival Glass Inexpensive pressed glass with vivid gold, orange, and purple iridescence, made in the United States between about 1895 and 1924. It is so called because it was frequently offered as fairground prizes.
Carving Removing excess molten glass off of the working piece.
Casing 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.
Casting Using a solid mold (plaster, sand…) to either pour hot glass into or pack in solid glass to be melted in a controlled oven
Charge To fill the furnace with glass, depending on the type of furnace this could take up to a few days.
Check A small crack on the surface of the glass.
Chill Mark An area on a hot worked glass piece, that has become slighlty cracked on the surface as a result of being over-exposed to steel.
Chord These are lines of clear glass that have a slightly different expansion coefficient enhance refract light at different rates.
Chunked A glass piece that has been badly damaged.
Cintra 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.
Clamp A tool sometimes used instead of a pontil to hold the closed end (usually the bottom) of a partly formed glass vessel while the open end (usually the mouth) is being shaped. See also Gadget.
Clapper 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.
Claw Beaker 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.
Clichy Rose A slice of a cane depicting an open rose. Canes of this type were frequently used in paper-weights made at the Clichy factory in France in the 19th century.
Clutha A type of glass with air traps and specks of aventurine, patented in the 1890s by James Couper, Christopher Dresser, and George Walton.
Coil Base A trail of glass drawn out to form a ring or conical foot on which the vessel stands.
Cold Colors Pigments applied as decoration to glass by cold painting.
Cold Painting 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. See also Enamel.
Cold Work Using grinding wheels, wet sanders, a diamond drills, U/V Glues… to shape, flaten or polish glass at normal temperatures.
Collar A ring that is used to hold the cane glass into place on a working piece.
Color Available for sale from several manufacturers, comes in either 1" diameter rods, powder, different size frits (chips), canes, sheet glass…..
Colored Glass 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.
Cookie A small amount of hot glass dropped onto the marver to be used as a foot.
A type of paperweight in which the slices of canes are arranged in concentric circles.
Cord An imperfection in the glass showing as either streaks, stones, or hazziness.
Core The form to which molten glass is applied in order to make a core-formed vessel. In pre-Roman times, the core is thought to have been made of animal dung mixed with clay.
Core Forming 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.
Cracking Off The process of detaching the unwanted portion of the parison from the blowpipe and the intended rim.
(French Crackle)
Dipping a piece while hot into a bucket of cold water will shatter the outside of the glass while leaving the inside intact, thus give the appearance of cracked glass
Crimper A tool used for decorating objects by giving them a crimped or wavy edge.
Crizzling, Crisseling 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.”
Crown Glass Sheet glass made by blowing a parison, cutting it open, and rotating it rapidly, with repeated reheating, until the centrifugal force has caused it to become a flat disk. After annealing, the disk is cut into panes of the required shape and size. Bull’s-eye panes come from the centers of the disks and preserve the thickened area where the parison was attached to the pontil.
Crown Weight A hollow paperweight that incorporates thin white or colored filigree canes arranged vertically on the sides and drawn together at the top.
Crucible The couldren (or bowl) that holds the glass inside the furnace
Crystal Lead based glass that is particularly well suited for grinding and engraving
Cullet Manufactured glassware that is unusable as a results of chips, cracks and problems can be bought by studio artists to be melted in their furnace as the primary source of clear (or color) instead of using batch
Cutting 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.
Cut-to-Clear Showing the under layers of the glass by cutting however many layers needed to complete the desired effect in the glass.
Day Tank A Furnace that can be used / charged daily
Decolorizer A substance (such as manganese dioxide or cerium oxide) used to remove or offset the greenish or brownish color in glass that results from (1) iron impurities in the batch or (2) iron or other impurities in the pot or elsewhere in the production process.
Depression Glass Inexpensive, machine-pressed American glassware made between about 1920 and 1950.
Devitrification (1) The process whereby glass becomes partly crystallized as it cools (usually too slowly) from the molten state; (2) the crystals formed by this process. Devitrification can also occur on the surface as a result of unsuccessful annealing or accidental heating to a high temperature. It is not caused by chemical reaction between glass and its environment, which is known as weathering.
Diamond Air Trap Decoration consisting of bubbles of air trapped in the glass in a diamond-shaped pattern. This is achieved by blowing a gather of glass into a mold with projections of the desired design, withdrawing it, and covering it with a second gather, which traps pockets of air in the indentations. This technique was patented by W. H., B. & J. Richardson of England in 1857.
Diamond Shears To evenly cut off a bit of glass, also to be used placement of bits
Diatreta A term used by Frederick Carder (1863-1963) to describe openwork objects that he made by lost wax casting.
Didymium Protective eyeware worn by glass artists have pink lenses to help cut down on the UV rays emitted by the furnace and gloryhole
Dip Mold 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.
Double Overlay Coating a glass works twice.
Duckbill Shears
Shears with an open edges, used to trim the lip of a blown vessel
Element (Annealer)
The electric cord or piece used to heat the annealer oven
Egyptian Blue A synthetic material, copper calcium tetrasilicate, with a distinctive blue color. In antiquity, Egyptian blue was made by heating together silica, lime, and a copper-containing ingredient. It is often confused with faience and misleadingly called frit.
Embossed Raised or lowered text or design on any surface of glass.
Enamel 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.
Encased Glass An object, such as a paperweight, that is covered with a layer of colorless glass.
Engraving 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. See also Carving, Cutting, and Stippling.
Etched Decoration Using acid to etch the glass. Strengthen or get an chemical reaction or effect with the glass surface.
Faceting The process of grinding and polishing an object to give the surface a pattern of planes or facets.
Faience A fired silica body containing small amounts of alkali, and varying greatly in hardness depending on the degree of sintering. It is covered with glaze, which may also be present interstitially among the quartz grains within the body. The term “glassy faience” is often used to describe a faience in which the reactions have proceeded to such an extent that the glass phase defines the visual appearance of the material.
Feathering Dragging a thread across a hot piece of glass thus creating a decrotaive effect similar to the top of a Napolean Desert (MY FAVORITE)
Fining The physical and chemical process of eliminating bubbles from the melt by raising the temperature to make the glass more fluid and adding fining agents such as arsenic and antimony.
Finisher The glass worker (generally the Gaffer) that puts the finishing touches on the glass before it goes into the Annealing Oven.
Finishing The process of completing the forming or decoration of an object. Finishing can take the form of manipulating the object into its final shape while it is hot, of cracking off before annealing, or of cutting, enameling, grinding, or polishing.
Fire Clay Clay capable of being subjected to a high temperature without fusing, and therefore used for making crucibles in which glass batches are melted. Fire clay is rich silica, but it contains only small amounts of lime, iron, and alkali.
Fire Polishing (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.
Firing 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).
Flameworking Using a table top torch and cold canes & tubes of glass in order to make a variety of glass objects
Flashing (1) The application of a very thin layer of glass of one color over a layer of contrasting color. This is achieved by dipping a gather of hot glass into a crucible containing hot glass of the second color. The upper layer may be too thin to be worked in relief. “Flashing” is sometimes used (erroneously) as a synonym for casing. (2) The act of reheating a parison by inserting it into a glory hole and then withdrawing it rapidly.
Flat Bouquet A decorative arrangement of canes in a paperweight. The canes imitate a bouquet of flowers and leaves, the flat top of which is parallel to the bottom of the paperweight.
Fluting The vertical lines, grooves or designs in the glass.
Flux A substance that lowers the melting temperature of another substance. For example, a flux is added to the batch in order to facilitate the fusing of the silica. Fluxes are also added to enamels in order to lower their fusion point to below that of the glass body to which they are to be applied. Potash and soda are fluxes.
Folded Rim A rim that has been folded to double its thickness and thereby increase its strength.
Foot-Ring A round disc usually found on the bottom of wine glasses, but can also be used on all types of vessels
Former Mold A mold with the same shape as the desired object, usually a vessel. Flat glass blanks are made into vessels by sagging them over or into former molds.
Founding The initial phase of melting batch. For many modern glasses, the materials must be heated to a temperature of about 2450°F (1400°C). This is followed by a maturing period, during which the molten glass cools to a working temperature of about 2000°F (1100°C).
Frax (FiberFrax) Spun Ceramic instulaion that is used in and around a glass studio, it is a white fluffy fabric, that is unsafe to the touch and very hazerdous to breathe
Free-Blown (off-hand blown) Glass Glassware shaped solely by inflation with a blowpipe and manipulation with tools.
Frigger The English term for an object made by a glassworker on his own time.
Frit or Fritting 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.
Frosting (1) A matte finish produced by exposing the object to fumes of hydrofluoric acid; (2) a network of small surface cracks caused by weathering.
Furnace Oven that holds liquid glass. Usually able to be opened and closed as more glass is needed. Sits around 2200 degrees farenheight
Fusing (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.
Gadget A metal rod with a spring clip that grips the foot of a vessel and so avoids the use of a pontil. Gadgets were first used in the late 18th century.
Gadroon A flutelike decorative motif, usually short in proportion to its width, that often approaches an oval form.
Gaffer The main team member of a glassblowing team. The person in charge of the project.
An oven that sits at a hot enough temperature to keep the glass moving, this allows atrists to create parts that can be stored for use later in the process
Gather Placing molten glass on the end of the blowpipe or pipe for the further development of that glass project.
Gathering The process of collecting the liquid glass from the furnace on the end of a blowpipe or punty. This is done by slow rotation in the glass.
Gathering Iron A long, thin rod used to gather molten glass.
Gemel A pair of bottles blown separately and then fused, usually with the two necks pointing in different directions.
Gilding The process of decorating glass by the use of gold leaf, gold paint, or gold dust. The gilding can be applied with size, or amalgamated with mercury. It is then usually attached to the glass by heat. Gold leaf can be picked up on a gather of hot glass.
Glazier A craftsman who paints and/or assembles glass windows.
Glory Hole Oven that is used to reheat glass as it is being worked. Usually the front is open for easy acces during the working of a piece. Sits around 2200 degrees farenheight
Grinding The technique of removing the surface of an object with a rotating wheel fed with an abrasive, or by some other means.
Grozing The process of breaking away the edge of a glass object with a grozing iron or pliers in order to shape it.
Hand Blown A glass project is handmade and was not assisted by machinery.
Hand Press A tool shaped like a pair of pliers, with flat jaws containing molds. Hand presses were used extensively in Europe for making chandelier parts. Later, they were introduced in the United States for pressing stoppers and bases.
Hard Glass A generic name for glass (e.g., borosilicate glass) with a relatively low coefficient of expansion. Soft glass (e.g., soda-lime glass), by contrast, has a relatively high coefficient of expansion.
Heat-Shaded Glass Glass that shades from one color to another. For example, Burmese glass shades from yellow to pink.
Heat Shield Using a paddle or something similar placed in between the working artist and the glass, providing a barrier that the heat will not penetrate.
The generic term for glass that is manipulated while it is hot.
Hydrofluoric Acid A highly corrosive acid that attacks silicates such as glass. Pure hydrofluoric acid dissolves glass, leaving a brilliant, acid-polished surface.
Ice Glass A decorative effect that causes the surface of the glass to resemble cracked ice. This is achieved by repeatedly plunging a parison of hot glass into cold water and withdrawing it quickly. The thermal shock creates fissures in the surface, and these impart a frosted appearance after the parison has been reheated to allow the forming process to continue.
Incalmo (Italian) The technique of constructing an object, usually a vessel, by fusing two or more blown glass elements. The process, first practiced in the Islamic world in the Middle Ages, demands great precision because the edges of the adjoining elements must have precisely the same diameter.
Inclusions A collective term for bubbles, metal and glass particles, and other foreign materials that have been added to the glass for decorative effects.
Inlay Any object embedded in the surface of a larger object. See also Marquetry.
Intaglio (from
Italian, “engraving”)
A method of wheel engraving whereby the ornamentation is cut into the object and lies below the surface plane. The German name for this technique is Tiefschnitt.
(French, “inserted”)
The process of applying two layers of decoration, the first being covered with a skin of glass that serves as the surface for the second.
Iridescence Spraying a shiny metallic finish onto hot glass.
Jacks Large tongs that are used in order to create score lines in the neck of a piece. It is the main tool used by glassblowers and can be used to perform a variety of tasks.
Kevlar Gloves High heat resistant gloves or big mittens that are used to carry the glass from the knock off table to the annealer.
Kiln An oven used to process a substance by burning, drying, or heating. In contemporary glassworking, kilns are used to fuse enamel and for kiln-forming processes such as slumping.
Kiln Forming The process of fusing or shaping glass (usually in or over a mold) by heating it in a kiln. See also Slumping.
Knock Off Table A table that the artist uses as a rest for a piece prior to putting it in the annealer. The table is usually lined with Fiber Frax.
Knurling A glass band or bead wrapped around a larger project.
Kuglar Oven
(Pick-Up Oven)
A small oven similar to the annealer that color can be preheated in prior to being used by the artist. Kuglar is a popular brand of color.
Lampworking see flameworking.
Lathe Cutting The technique whereby a blank in the general shape of the finished object is mounted on a lathe and (in antiquity) turned with the aid of a bow or handled wheel, while a tool fed with abrasive is held against the surface in order to polish it, modify the profile, or cut it.
Latticino Venetian cane that is used to decorate outside of glass. The inside of the cane usually has intricate designs which add to the overall design of the piece. AKA Zanfirico.
Layered Glass Glass containing layers of different colors. Decorative effects can be obtained by revealing the contrasting colors by acid etching, carving, cutting, or engraving.
Leaf, Silver / Gold Paper thin gold or silver that can be used in surface decoration.
Lehr or Leer The oven used for annealing glassware. Early lehrs were connected to the furnace by flues, but the difficulty of controlling heat and smoke made this arrangement impracticable. Later lehrs were long, bricklined, separately heated tunnels through which the glass objects were slowly pushed. The glass remained in the lehr for several hours, while it was gradually reheated and then uniformly cooled. Today, lehrs work on a conveyor belt system.
Lily-Pad Decoration Decoration consisting of a gather around the base of the vessel, which has been drawn upward in four or more projections with rounded ends. Lily-pad decoration was introduced to America by German glassworkers. It became popular in New England, New York, and New Jersey in the second quarter of the 19th century.
Lime 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.
Linen Smoother An object believed to have served as a pressing iron. The earliest linen smoothers date from the Middle Ages, and the latest were made in the 18th century.
Lion-Mask Stem A hollow stem made by blowing the gather into a mold patterned with two lion’s masks, usually separated by festoons. Lion-mask stems, first used in Venice in the 16th century, subsequently became one of the hallmarks of façon de Venise glass.
Lip Wrap The top edge of the piece. This is the part that is opened with the jacks (The edge one would drink from on a tumbler or cup).
Lipper A glassworker’s tool made of wood in the shape of a cone and with a handle. It is used to form the lip at the mouth of a vessel.
Luster (1) A shiny metallic effect made by painting the surface with metallic oxides that have been dissolved in acid and mixed with an oily medium. Firing in oxygen- free conditions at a temperature of about 1150°F (600°C) causes the metal to deposit in a thin film that, after cleaning, has a distinctive shiny surface. Strictly speaking, this process is a form of staining. (2) A glass lighting device, such as a candelabrum or candlestick, decorated with hanging prismatic drops.
Maestro An italian glass master.
Mandrel In glassworking, (1) a lathe shaft with a hollow end, designed to receive spindles; (2) a metal rod around which beads and other small objects can be formed.
Marbled Glass Glass decorated with streaks of two or more colors, resembling marble. Marbled glass was a Venetian specialty from the 15th to 17th centuries, but it was also made in other times and places. Venetian marbled glass is known as calcedonio.
Marver A steel (or marble) table that is used to shape the glass. The artist can roll the glass on this table to achieve a variety of goals, most of which have to do with shape.
Marquetry A decorating technique whereby pieces of hot glass are applied to still molten glass and marvered into the surface, creating an inlaid effect. After the glass is cooled, it is possible to further emphasize these areas by carving and engraving. See also Inlay.
Marver (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.
Matte Finish A non-shiny finish made by grinding, sandblasting, or exposing the surface to fumes of hydrofluoric acid. See also Frosting.
Metal A term frequently used as a synonym for glass. It is misleading because glass is not a metallic substance, and its use is discouraged.
Metallic Oxide 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. See also Iridescence and Luster.
(Italian, “half-mold”)
A term applied to the process of making vertical ribs on the lower part of a blown glass object by gathering additional glass on the parison and inflating it further in a dip mold. This technique is also known as mezza stampatura or, in Muranese dialect, meza stampaura.
Mirror Monogram A monogram written in such a way that each letter is reversed to produce its mirror image, the letter and its image being combined to give a symmetrical ornamental form.
Mold Blown An open ended cylindrical designed to create effects or grooves in the molten glass by blowing into the blowpipe while in the mould vertically.
Moil The unwanted top of a blown object. When the last stage in the forming process is the removal of the object from the blowpipe, the result is a narrow opening that almost certainly is not what the glassblower desires. After annealing, therefore, the top of the object is removed, usually by cracking off. The moil from a mold-blown object is often known as an overblow.
Moil-Wrap A bit of hot glass that is wrapped around the moile to keep it from breaking / cracking.
Mold 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.
Mold Blowing 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.
Mold Pressing Forcing hot glass into an open or multipart mold by means of a plunger.
Mosaic A surface decorated with many small, adjoining pieces of varicolored materials such as stone or glass.
Mosaic Glass 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.
Muff A glass cylinder intended to be cut into sheets.
Muffle Kiln A low-temperature kiln for refiring glass to fuse enamel, fix gilding, and produce luster.
Murini Glass tiles and round tiles that are fused together in glass coloration designs, usually they are quite intricate.
Natron Sodium sesquicarbonate, originally obtained mainly from the Wadi el-Natrun, northwest of Cairo. It was commonly used by Roman glassmakers as the alkali constituent of batch.
Neck The edge of the piece that will be scored and seperated when transfering the working piece onto the punty.
Newspaper Soaked newspaper the artist uses to grab hold of the glass and squeeze in the shape they are looking for.
Nipt-Diamond-Waies The technique of manipulating adjacent vertical ribs with pincers to form a diamond pattern. “Nipt-diamond-waies” was the term used by the English glassmaker George Ravenscroft (1632-1683) in a 1677 advertisement for his new lead glass.
Obsidian A volcanic mineral that was the first form of natural glass used by humans. It is usually black, but it can also be very dark red or green; its splinters are often transparent or translucent.
Openwork Work that is perforated. Openwork in glass objects can be made by creating a network of trails, by casting, or by cutting.
Optic Mold A steel or bronze mold that puts ridges or other shapes into the vessel, Optic Molds are used early in the process.
Overblow A by-product of mold blowing, this is the portion of the parison that remains outside the mold. The overblow, or moil, is usually removed by cracking off.
Overlay A layer of glass that covers a layer of a different color, often as the result of casing or flashing.
Overshot Glass Rolled molten glass is covered with splinters covering the surface as a final completed surface.
Pacioffis Wooden jacks used to open up large pieces like bowls
and plates.
Paddle A wooden tool used to flatten the bottom of a piece.
Pallet A glassworker’s tool consisting of a square piece of wood or metal and a handle. It is used to flatten the bases of vessels.
Paperweight 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.
Parison A gather, on the end of a blowpipe, that is already partly inflated (from French paraison) .
Pasterelli A flat plate mounted on a steel rod that can be used to hold latticino glass, sheet glass, murini and glass components, while they are in the gloryhole.
Pâte de verre
(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.
Pattern Mold Glassware that has been blown into a mold whose interior has a raised pattern so that the object shows the pattern with a concavity on the inside, underlying the convexity on the outside. Pattern molds are not used to impart the final form to the object.
Pegging The process of pricking molten glass with a tool that leaves small, air-filled hollows. When the glass is covered with a second gather, the hollows become air traps. This technique is used to decorate knops and paperweights.
A technique whereby a hot parison is rolled in chips of glass, which are picked up, marvered, and inflated.
Piece Mold A mold made of two or more parts.
Pillar-Molded Glass A term used by 19th-century English glassmakers to describe vessels with mold-blown vertical ribs but no corresponding indentations on the interior. This effect was achieved by partly inflating the gather, allowing it to cool sufficiently to become somewhat rigid, and then gathering an outer layer of glass around it. The parison was then further inflated in a ribbed dip mold, which shaped the soft outer layer without affecting the inner layer. The term is frequently but incorrectly applied to ancient Roman ribbed bowls, which were made in a different manner.
Pincers A glassworker’s tool used for decorating objects by pinching the glass while it is hot.
Pipe Warmer a small gas oven that is used to preheat the steel pipes; many glory holes have pipe warmers built into the side.
Plating A 19th-century American synonym for casing.
Polishing 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.
Pontil, 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.”
Post The glass used to attach a second pontil to glass that is about to be pulled into a cane.
Post Technique Instead of being applied to a vessel with a wad, the pontil is attached to a flat plate of glass called a “post,” which is then affixed to the base or footring of the vessel.
Pot A fire-clay container in which batch is fused and kept molten. The glassworker gathers glass directly from the pot.
Potash Potassium carbonate. It is an alternative to soda as a source of alkali in the manufacture of glass.
Pot Furnace A furnace that the glass sits inside a crucible which sits inside the furnace. If the Crucible breaks, it can be
easily replaced.
Pressed Glass 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.
Printy, Printie A circular or oval wheel-cut depression. A decorative pattern of long, mitered grooves, cut horizontally in straight lines so that the top edges of each groove touch the edges of the adjoining grooves. Prismatic cutting is usually found on the necks of pitchers and decanters.
Prunt A blob of glass applied to a glass object primarily as decoration, but also to afford a firm grip in the absence of a handle.
Pulegoso (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.
Punty A solid steel rod that is used for bits and for the transfer process of the piece from on the blowpipe to the "punty".
Pyrex 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.
Pyrometer High heat thermometer used to measure temp inside furnace or gloryhole.
Quincunx (from Latin, “five-twelfths”) An arrangement of five objects in a square or rectangle, with one at each corner and one in the middle, like the five spots on dice. Prunts and other motifs are sometimes arranged in a quincunx pattern.
Raised Diamond
An allover pattern of raised four-sided diamonds of pyramidal form, each with a sharp apex, cut with a mitered wheel. It was produced by English and Irish glass cutters between about 1780 and 1825.
Rag Tick layers of wet newspapers folded to provide a cool safe pad for the glassworker to shape the hot molten glass.
Raspberry Prunt A flat, circular prunt with an impressed design resembling a raspberry.
Reducing Atmosphere An atmosphere in a kiln or furnace that is deficient in oxygen. Sometimes, a reducing atmosphere is created deliberately to reduce oxides to their metallic state, as in the case of luster pigments.
Refractory A substance, usually clay with a high silica content, capable of resisting high temperatures. Furnaces and pots are made from refractory materials.
Relief Cutting A type of cut glass with decoration in high relief, made by removing the background.
Reheat to heat the glass back to a molten state; usually done
in the gloryhole.
Resist A substance that resists or prevents a particular action. During the process of acid etching or sandblasting, parts of the surface are protected with a resist.
Reverse Foil Engraving A decorative technique in which gold or silver leaf is applied to the back side of a piece of glass, engraved, and protected by varnish, metal foil, or another piece of glass.
Reverse Painting The term applied to a number of decorative techniques, all of which involve painting, on the back side of the glass, a design that is viewed from the front (that is, through the glass). Because of this, the painter must apply the pigments in the reverse of the normal order, beginning with the highlights and ending with the background.
Rigaree A raised band or pattern of bands, usually made by crimping applied trails.
Ringer The glass worker that applies the ring for glass to the
larger piece.
Rock-Crystal Engraving A style of copper-wheel engraving that, combined with polishing, gave glass objects the appearance of rock crystal. The style was introduced by Thomas Webb & Sons of England in the 1870s.
Rod A monochrome segment of glass cut from a trail.
Rod Forming The technique of winding molten glass around the tip of a narrow metal tool or wire coated with clay or kiln wash to act as a separating agent. It is used for making narrow objects such as beads and pendants.
Roman Foot A flangelike base formed by folding. The ancient Romans were the first glassworkers to make bases in this manner.
Rondelle A flat blown glass that was spun hot.
Rotary Polishing The process of polishing an object with tools and an abrasive while turning it on a lathe.
Sandblasting A method used to remove layers of glass. A cloudy dull finish will result with every layer removed. Some artist use the sandblasting process to remove enough glass to actually go through the glass for different effects.
Satin Glass A acid matt finish or frosting.
Sawing Cutting glass with a rotating wheel with a blade usually diamond tipped.
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.
Sand Casting,
Sand Molding
A forming technique in which molten glass is poured or ladled into a mold of compacted sand. A rough-textured granular surface results where the glass comes into contact with the sand.
Satin Glass A 19th-century term for glass with a matte finish.
Scale An accidental inclusion in glass, consisting of corrosion products detached from the metal implements used to stir the batch or to form the object.
Scavo (Italian, “excavation”) A technique involving the application, to the surface of an object, of substances that, when heated to about 1470°F (800°C), fuse and create an effect similar to weathering, thereby imitating glass from an archeological excavation.
Schmelzglas (German, “enamel glass”) A term applied to several types of decorative glassware, including calcedonio and opaque white glass with a red overlay applied by flashing. It does not refer to glass decorated with enamel.
Seam Mark A slight, narrow ridge on a glass object, which indicates that it has been made in a mold. The seams appear where gaps in the joins between parts of the mold have permitted molten glass to seep during formation. On well-made pieces, the seam marks are usually smoothed away by grinding or fire polishing.
Seeds Small air bubbles found in glass that has not
been squeezed.
Sculpting Handmade free forming solid glass works designed while in molten glass form.
Shard Glass fragments usually colored of which would be rolled or melted into a working piece for the additions of colors of textures is not melted all of the way. Different colors melt at different temperatures lending creative textures with variation.
Shears Glassmakers scissors that are used for the cutting, trimming and shaping of hot glass. Usually very primitive in design with heavy gage steel.
Shearings Slivers of waste glass formed by trimming glassware during manufacture.
Silesia The main ingredient of glass used for art glass.
Silica Silicon dioxide, a mineral that is the main ingredient of glass. The most common form of silica used in glassmaking has always been sand.
Silveria Is a type of art glass with incased silver foil.
Silver Stain A deep yellow stain made by painting the surface of the glass with silver nitrate or similar compounds and firing it at a relatively low temperature.
Silvered Glass 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.
Sintering The process of heating a mixture of materials so that they become a coherent mass, but not melting them.
Size In glassworking, the name applied to several glutinous materials, such as glue and resin, used to affix color or gold leaf.
Slumping 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.
Smalt Colored glass, often deep blue glass colored with cobalt oxide. Smalts are finely ground to use as colorants for glass and enamel.
Soda 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.
Sodium Flare The bright light that is given off of the reaction of oxygen rich flame and the sodium of the glass in a kiln. Didymium glass in the glasses to avoid serious damage to the vision of one’s eyes. Usually, Flame-workers Lamp-workers are at the primary concern here.
Soffietta (Italian) A tool used as a puffer to further inflate a vessel after it has been removed from the blowpipe and is attached to the pontil. It consists of a curved metal tube attached to a conical nozzle. The glassblower reheats the vessel, inserts the nozzle into its mouth so that the aperture is blocked, and then inflates the vessel by blowing through the tube.
Soft Glass A generic name for glass (e.g., soda-lime glass) with a relatively high coefficient of expansion. The term hard glass (e.g., borosilicate glass) refers to glass with a relatively low coefficient of expansion.
Soliflore A French term for a vase with a bulbous body and a long drawn out neck for a single flower.
Spatter Glass The glass with flecks of contrasting color rolled into it.
Sputtering A metal coating process for the glasses surface.
Squeeze The process of getting seeds out the glass, by cooling the glass in the furnace and then reheating it, the air bubbles are forced out the top of the glass AKA Fining.
Staining 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.
Steam Stick a cone shaped piece of wood and is used in place of a soffietta, instead of blowing the steam stick uses the water soaked into the wood to creat steam which can push the glass out.
Stick Lighting, Stickwork The process of using a point to scratch internal details in painted or enameled decoration.
Stippling (1) The technique of tapping the surface of a glass object with a pointed tool, often with a diamond or tungsten-carbide tip. Each tap produces a mark, and the decoration is composed of many hundreds or thousands of marks. (2) On lacy-pattern glass, the stippling is part of the decoration of the mold.
Stone 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.
Strain Cracks Fissures in the body of a vessel caused by internal strain resulting from inadequate annealing and/or accidental thermal shock.
Straight Shears To cut a straight line or bit.
Stretch Glass A cracked iridescence on the surface.
Striking The process of reheating glass after it has cooled, in order to develop color or an opacifying agent that appears only within a limited range of temperatures.
Stringer Like cane but applied from a molten glob of color over the surface of hot glass.
Sulphide A small ornamental object of white porcelainlike material, made to be encased in glass. The term is also applied to objects that are decorated with sulphides. They were popular in Europe and America throughout the 19th century. The term “sulphide” is probably connected with the use of sulfur by 18th- and 19th-century moldmakers.
A pattern of spiraling vertical ribs made by inflating the parison in a dip mold with vertical ribs, withdrawing it, and twisting it before continuing to inflate. The pattern is also described as wrythen.
Taglia (Italian) A square-ended knife used to shape or sculpt molten glass on the blowpipe.
Tank A large receptacle constructed in a furnace for melting batch. Tanks, which were first used in antiquity, replaced pots in larger glass factories in the 19th century.
Teardrop A glass shape that is usually blown from above and allows a consistent growth of a glass blown into it.
Thermal Shock The cause by a sudden shift of temperature hot or cold causing the glass to break, crack or shatter.
Thermocouple Bimetal probe that measures the kiln’s temperature.
Threading 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.
Threading Wheel A pipe rest that uses ball bearings to spin the pipe evenly backward allowing the artist to evenly apply a spiral down the piece.
Tongs Glassmakers tool for picking up, transferring and applying water to the Punty to remove the glass piece from the pipe of blowpipe.
Trail A strand of glass, roughly circular in section, drawn out from a gather.
Trailing The process of applying trails of glass as decoration on the body, handle, or foot of a vessel. It is done by laying or winding softened threads on a glass object during manufacture. See also Combed decoration.
Tweezers To be used to pinch and pull glass.
Twist A type of decoration in the stems of 18th-century and later drinking glasses, made by twisting a glass rod embedded with threads of white glass, threads of colored glass, columns of air (air twists), or a combination of all three.
Undercutting 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).
Vermiculée (French, “vermiculate”) Design A convoluted ground pattern resembling worm tracks.
Verre églomisé (French) A decorative technique in which gold or silver leaf is applied to the back side of a piece of glass, engraved, and protected by varnish, metal foil, or another piece of glass. The name is derived from the French mirror and picture framer Jean-Baptiste Glomy (d. 1786). Decoration of this type, however, had been made since the 13th century, and the term reverse foil engraving is preferable.
Virtual Production Replications The remaking and replacement of an unattainable (non-art) original "production" glass piece with an as close as possible custom made glass piece for repair, recovery or restoration for historic purposes, etc.
Waster A defective object discarded during manufacture. Wasters are routinely recycled as cullet.
Wax Bees Wax and or Carnuba wax is used to coat the jacks so that they don't stick to the glass.
Weathering Changes on the surface of glass caused by chemical reaction with the environment. Weathering usually involves the leaching of alkali from the glass by water, leaving behind siliceous weathering products that are often laminar.
Wetting Off The separation line for the glass work from the blowpipe or pipe uses cold water to fracture control the break and separation.
Wheel Engraving 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.
Wraps A string / spiral of glass that is added on to the main piece. Can be melted into the piece or can be left 3 dimensional.
Yoke A stand in front of the gloryhole that is used as a support for the blowpipes. Using ball bearings it allows the artist to turn the pipe easily with little effort giving them a chance to regain strength.
Zanfirico (Italian) A type of polychrome cane made by assembling a bundle of rods of different colors, and heating it until it is soft. The bundle is then attached to two pontils and elongated by drawing. At the same time, the bundle is twisted to produce a spiral pattern. Zanfirico, which is a synonym for vetro a retorti, takes its name from the Venetian dealer Antonio Sanquirico, who, in the 1830s, encouraged the revival on Murano of this and other traditional techniques.
Zwischengoldglas (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.
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