Art Glass Terms

Annealing

Cooling the formed glass product at a controlled rate of temperature change for the purpose of relieving thermal stress. The appropriate cooling curve varies with glass type and formed shape, especially thickness.

Antique

A. Full Antique: Term applied to art glass produced by the historical mouth-blown cylinder method. The craftsman blows a glass cylinder which is annealed and cooled. The cylinder is then scored lengthwise, separated, re-heated and folded out into a flat sheet. Common characteristics include attractive linear striations and a very pristine surface.

B. Drawn Antique: Also called semi-antique, machine antique or new antique. A simulated full-antique produced by the Vertical Draw method (see Sheet Forming Methods). The textural striations are mechanically applied. Quality is excellent and cost is less than full antique. GNA (German New Antique) is a common example.

C. Scribed Antique: A simulated full antique produced by the Double Roll method (see Sheet Forming Methods). The linear striations are scribed into the hot glass surface. Quality is excellent and cost is considerably less than full antique. Introduced by Spectrum® Glass in 1996 under the trade name Artíque®, and now produced by Oceanside Glass and Tile®.

Artíque®

See Scribed Antique, above.

Baroque™

A machine made “reamy” glass, created by combining glasses of mis-matched compositions. The different glasses “oppose” each other when they are stirred together, creating artistic 3-D swirls. An Oceanside exclusive.

Bent (or Slumped) Glass

Glass which has been heated in a kiln from room temperature to a temperature high enough to cause it to soften and slump (sag) into or over a mold. The finished item takes the shape of the mold. Also called “curved glass.”

Bevel

Cold glass (usually clear, thick plate) with edges that have been ground and polished to an angle other than 90 degrees. Transmitted light is refracted and a prism-like effect results. Bevels are available in a variety of sizes, shapes and geometric configurations (called “clusters”) for incorporation into leaded glass work.

Billet

A glass ingot, similar to a dalle, used in glass casting.

C.O.E.

See Coefficient of Expansion.

Came

Channeled strips of lead, zinc or other metal used to bind glass pieces within a design. (See Leaded Glass.)

Cane

A cane is a long and narrow piece of glass, usually in the form of a rod (round in cross-section). Canes are made by stretching a mass of hot glass to the desired thickness, and are often made with encased designs that can be seen from the side or when cut in cross section.

Cast Glass

A glass art medium in which glass is melted in, or melted and then poured into, a pre-shaped mold to create a desired shape, often with great detail. Frit casting is a popular form of casting on a smaller scale using molds made for the purpose. Finished frit castings can be stand-alone art or can be incorporated into other fused work.

Cathedral Glass

Describes transparent glass that is monochromatic—i.e., single color sheet glass, with smooth or textured surfaces.

Catspaw

(Single Roll forming method.) A surface texture resulting from the chilling of hot glass on a cool table. The appearance is likened to the paw prints of a cat.

Coefficient of Expansion

The ratio of the change in length or volume of a glass to its original length or volume per unit change in temperature. Used to help determine compatibility of different glasses for the fusing process. (See Compatible and Tested Compatible.)

Confetti

Eggshell-thin glass shards, made by shattering thinly blown colored glass. Confetti can be incorporated into a fused or blown glass design.

Combing

A process in which a rake-like tool is drawn across molten glass to create artistic patterns.

Compatible/Compatibility

Glasses are said to be compatible if, after being fused together by blowing or kiln forming and properly annealed, they remain relatively free from internal stress. (See Coefficient of Expansion.)

Copper Foil

Thin, narrow strips of adhesive-backed copper tape used to wrap the edges of glass pieces that have been cut to fit a pattern. Once wrapped, solder is applied, bonding the glass pieces together. Assembling a stained glass project in this manner is called the “copper foil technique.” Louis Tiffany is credited with its development.

Crackle

(Blown Cylinder method.) The hot cylinder of glass is dipped in liquid, causing radical, random fissures in the glass. The cylinder is then reheated and further blown to heal the surface fissures. Resulting surface resembles the texture of alligator skin.

Dalles

Thick (usually 1”) slabs of cathedral glass.

Dalle de Verre

An art glass medium in which dalles are broken into pieces with a carbon hammer and set in an epoxy base to adhere them in a decorative design. Dependent on large scale for best appearance, they are primarily used in architectural applications such as church walls.

Dichroic

Commonly used term to describe glasses that have been coated with one or more ultra-thin crystalline layers of transparent metal oxides designed to enhance reflections at specific wavelengths of light. The process occurs in a vacuum chamber at elevated temperatures. The resulting effects are striking and brilliant color reflections at varying angles of incidence.

Drapery Glass

Glass sheets with multiple dramatic folds, likened to those in hanging drapes.

Expansion Coefficient

A numerical designator assigned to a glass to describe its Coefficient of Expansion.

Flashed

Glass of one color with a very thin layer of another color on one side. Flashed glass is often used for etched or sandblasted glass art. When sections of the thin color layer are removed, the base color shows through.

Fiber Paper

Heat-resistant ceramic products that range from paper-thin to ¼-inch thick. Products can be used to protect a kiln shelf (Papyros® kiln shelf paper for example), used in damming, or to help create shapes in glass fusing and slumping processes.

Flux

Chemical agent (liquid or paste) used to facilitate the flow of solder and prevent formation of oxides during soldering.

Frit

Frit is crushed glass, ranging in particle size from a fine powder (F1) to sizes useful in mosaic work (F7). While frit is sometimes used as a raw material in glass manufacture, it is known to artists as a coloring agent or used to create decorative effects in blowing and fusing. Frit is often used in fusing to produce a look similar to painted works of art.

Fused Glass

Glass forms produced by placing different pieces of glass in contact with each other in an arranged design, then firing them in a kiln at a temperature high enough to fuse them into one piece of glass. Also known as “kiln-formed glass.”

Fractures & Streamers

In the single roll process (see Sheet Forming Methods), thin glass chips or shards (fractures) and/or glass string (streamers) are arranged on the casting table before the glass is poured, and thus pressed into the glass sheet as it is formed.

Glob

See Nugget.

Glue-Chip

A texture created on the surface of cold glass by applying hot animal glue and allowing it to dry under controlled temperature and humidity conditions. As the glue dries and contracts, it chips the glass surface in a lacy, organic and attractive pattern, similar to frost on a window pane.

Gold Pink

Common name for colored glasses in the pink/cranberry/fuchsia range that require gold oxide as a coloring agent.

Hand Cast Sheet Glass

Sheet glass produced by the single roll method (see Glass Sheet-Forming Methods).

Kiln-carving

Although not really “carving,” kiln-carving is a technique that creates the appearance that part of the glass surface has been carved away. The process is usually achieved using thick ceramic fiber paper that is cut and placed underneath the glass when it’s fired in a kiln. The glass is heated hot enough to allow the glass to form around the cut fiber shapes to take on the desired design.

Iridescent

Surface treatment in which a layer of metallic oxide is bonded to the hot glass surface just after sheet-forming, resulting in a colorful, shimmering effect.

Jewel

A piece of glass that has been cut and faceted or press-molded into a geometric shape like a jewel. Often incorporated into leaded glass artwork.

Leaded Glass A.

Sheet glass pieces joined with metal strips, usually made of lead, called “came.” Solder is applied to the joints of the came to bond the work together. B. Glass containing lead as a raw material (as in “leaded crystal”).

Millefiori

Italian for “a thousand flowers.” Commonly refers to glass objects made from masses of murrini slices.

Mosaic

A picture or decorative design made by setting small pieces of a hard material (such as glass, tile, or stone) onto a surface.

Mottled Glass

An opalescent glass in which rates of crystal growth have been controlled to create areas of opacity on the surface in a visually mottled effect. See also Ring Mottle.

Murrini

A thin slice of complex, patterned glass cane that can be used as a component in another glass object.

Noodle

A thin and flat, fettuccini-like, length of glass used as a decorative element in the hot glass arts.

Nugget

(See also Glass Blowing Nuggets.) A small, irregularly shaped “glob” of glass, flat on the bottom, rounded across the top. Nuggets are made by literally dropping a small amount of molten glass onto a flat surface. Frequently called “globs,” they are often incorporated into leaded glass artwork, or created from tested compatible glass for fused work.

Oceanside Compatible™

A line of tested-compatible products for the hot glass arts made by Oceanside Glass and Tile®. Oceanside Compatible products are formulated with the COE of 96 and are fully compatible with System 96® products.

Opal or Opalescent

Said of any glass into which a raw material has been introduced into the formulation (usually fluorine or phosphorus) which causes a degree of crystallization to occur, and creates opacity in the glass. (Reflected light is colorless, therefore white.) The degree of opacity (and “whiteness”) is variable depending upon composition and temperatures used in the manufacturing process. White glass is commonly called “opal.”

1. Solid Color Opalescent Glass: Glass which is both colored and crystallized, made into a single color sheet. Sometimes called “opaque” glass.

2. Mixed Opalescent Glass: White glass (opal) mixed with one or more other colors to create a variegated, multi-colored sheet. Light transmission varies with composition. Also called “variegated opalescent,” sometimes “streaky” or “wispy.”

Painted Glass

Glass on which special paints (containing frit) have been applied in illustration or decorative pattern and then heated in a kiln to a temperature high enough to fuse the pigments permanently to the glass surface. The modern version of the original medieval “stained glass.”

Pate de Verre

An art glass medium in which powdered glass frits are spread in a decorative design, then fired in a kiln.

Reamy

Descriptive of Full-Antique glass with a wavy irregular surface.

Refactory

High-temperature brick used to construct ovens for melting glass.

Ring Mottle Glass

An opalescent glass in which rates of crystal growth have been controlled to create ring-shaped areas of opacity on the surface.

Ripple

A surface texture, often dramatic, consisting of linear or irregular ripples. Created naturally in some sheet-forming processes, imitated with an embossing roll in others.

Rods

Used to describe cylindrical, pencil-thick sticks of glass used primarily in torch-working and glass bead making. They are available in a wide color range and many expansion coefficients. “Rod dots” are small (1/4-inch or less) nipped pieces of rod or cane used in fusing.

Rondel

A mouth-blown piece of glass that has been spun into a circular shape, often irregular. Sometimes incorporated into leaded glass artworks. Machine-made facsimiles are common, and are known as "pressed rondels."

Seedy Glass

Glass in which air bubbles are entrapped. Air or gas is injected into the molten glass prior to forming the sheet.

Semi-Translucent Glass Sheets

Oceanside-produced sheet mixes that have predominantly opalescent content, therefore allowing less light to pass through the sheet, or pass through in only small areas.

Slumped Glass

Glass which has been heated in a kiln from room temperature to a temperature high enough to cause it to soften and slump (sag) into or over a mold. The finished item takes the shape of the mold.

Solder

A fusible alloy, usually tin and lead, used to join metallic parts, or the act of applying it. Used to bond metals in both the leaded and copper foil techniques of stained glass work.

Stained Glass

Commonly used to describe any colored flat glass or any object made of such glass joined by metal strips. The term originally applied to colored or clear flat glass cut to fit an artist’s design, on which details were painted in pigment with a brush. The glass pieces were then heated in a kiln or oven to bond the pigment to the glass surface. This firing makes the painted detail as durable and permanent as the glass itself. Most religious windows from medieval times until the 20th century were executed in this manner, and so the term came to be used first for any architectural application, and then for any design in colored flat glass. It is now universally accepted as a convenient general term to define the art, the craft, and the industry.

Streaky Glass

Two or more colored glasses mixed together to create a multi-colored glass sheet in which each color can be seen separately as well as where they intersect to make new color(s).

Stringer

A thin, spaghetti-like, strand of glass used as a decorative element in the hot glass arts.

Studio Nuggets™

Uniform clear glass pellets used as a raw material in glass blowing, glass casting, and fusing. Part of the Oceanside Compatible™ family of tested compatible products.

System 96®

Tested compatible products for the hot glass arts that are now produced by Oceanside Glass and Tile® under the name Oceanside Compatible™.

Terrazzo

A combination of marble, granite, onyx, or glass chips in a binder of portland cement or other resinous material. After curing, the surface is ground to expose the decorative chips.

Tested Compatible

Descriptive of glasses which have been tested and marked prior to sale to verify compatibility with each other when combined in a hot glass process like blowing, fusing, or casting.

Textured Glasses

1. Rolled textures: In rolled glasses (see definitions below), one of the forming rolls is embossed with a texture that is imprinted on the glass as the sheet is formed. This produces glass smooth on one side and textured on the other. Common examples are “hammered,” “granite,” and “muffle.”

2. Natural textures: any textural effect created without mechanical influence or embossed rolls. Includes Baroque and Waterglass®.

3. Cold glass textures: this category includes glue chipping, etching, sand blasting, and any other surface treatment performed on the cold glass sheet at room temperature.

Tools Used in Glass

Nippers — A bit like “scissors” for glass, the nippers chew up glass with ease, creating a characteristic curvy break that’s artistic and versatile. 
Aim flying nips into a container, and always wear safety glasses.

Glass Cutter — The cutter’s wheel creates a “score” as it’s guided across the glass surface. When pressure is applied to both sides of this score, the glass will break. There are many cutter grip styles from which to choose.

Running Pliers — These specially designed pliers put pressure on both sides of the glass cutter’s score, encouraging a “run” (crack) along the line of the score. Often the glass will break all the way along the score with just gentle pressure from this tool.

Breaking (or Grozier) Pliers — These sturdy pliers act like metal fingers, to grab, pull, and break the glass along the glass cutter’s score line. Especially useful for small pieces, or to nibble off pointy spots.

Translucent Glass Sheets

These Oceanside-produced mixed sheets are made of both transparent and opalescent glass but contain a higher amount of transparent glass, allowing light to pass through in many or most areas.

Waterglass®

An Oceanside exclusive. A natural surface texture created by stretching the hot glass sheet while it is still in a malleable state. The result is gentle, rolling waves that resemble the surface of a lake or stream.

Wispy Glass

Transparent glass with thin wisps of opalescent white stirred into the sheet.

Glass Manufacturing Process Terms
Annealing

Cooling the formed glass product at a controlled rate of temperature change for the purpose of relieving thermal stress. The appropriate cooling curve varies with glass type and formed shape, especially thickness. Directly related to glass cutability.

Batch

The mixture of granular raw materials that is prepared and put into the melting furnace to create a given glass — for manufacture or blowing. The primary raw materials for clear glass are silica sand, soda ash and limestone. Cullet is also often used.

Continuous Furnace

A glass melting furnace which is continuously full of molten glass. The introduction of batch (raw materials) into the furnace displaces existing molten glass and forces it out of the furnace and through the forehearth to the forming process. The process continues for the life of the furnace. (See Process Diagram.)

Cullet

Crushed glass scraps, generally created as a by-product in glass making, can also be crushed glass specifically produced per a customer’s request. Some glass makers use cullet from other sources or from glass recyclers as a major raw material in their own batches.

Day Tank

A glass-melting furnace that is designed to operate on a 24-hour cycle. The batch is added to an empty furnace at a rate that allows it to melt properly, until the furnace chamber is full. Then, after suitable “cookout” has occurred, the molten glass is used to make product. When the furnace is empty, the cycle is repeated.

Forehearth

A shallow chamber through which molten glass passes on its way from a continuous melting furnace to the forming process. The purpose of this chamber is to allow the temperature of the glass to drop from melting temperatures (about 2,700°F) to forming temperatures (about 2,200°F for 1/8” thick sheet glass).

Lehr

An enclosed chamber through which formed glass products are carried for the purpose of annealing.

Pot Furnace

A melting chamber in which one or more ceramic pots are placed. Batch is fed into the individual pots through ports in the chamber walls, and when melted, glass is ladled from the pots via the same ports. Each pot is fairly small. The pot furnace allows the melting of a number of different glass colors (as many as there are pots) at the same time, within a single melting chamber.

Glass Sheet Forming Methods
Blown Cylinder

Method Term applied to art glass produced by the historical mouth-blown cylinder method. The craftsman blows a glass cylinder which is annealed and cooled. The cylinder is then scored lengthwise, separated, re-heated and folded out into a flat sheet to create “Full Antique” glass. Common characteristics include attractive linear striations and a very pristine surface. See Full Antique.

Single Roll Method

Molten glass is poured onto a metal table and a single metal roll is used to flatten it into a sheet. Sometimes called “hand cast” sheet glass.

Double Roll Method

Molten glass is passed between a pair of rotating metal rolls to form the sheet.

Vertical Draw Method

Molten glass is pulled up vertically through a slit in a large one-piece refractory block that is floating on the glass surface. The annealing lehr is mounted vertically over the draw chamber. Drawn glass is generally more pristine than rolled glass because its surface has remained untouched during forming.

Float Process

Molten glass is pulled from the forehearth atop a bath of molten tin. The process produces a perfectly smooth sheet of uniform thickness in high volume. The float process is used to produce virtually all common window glass today, thus the term “float glass.” Not used for art glass production.