Acid Etching - This process for the decoration of glass involves the application of hydrofluoric acid to the glass surface. Hydrofluoric acid vapors or baths of hydrofluoric acid salts may be used to give glass a matte, frosted appearance (similar to that obtained by surface sandblasting), as found in lighting glass. Coating the glass with wax and then inscribing the desired pattern through the wax layer can produce glass designs. When applied, the acid will corrode the glass but not attack the wax-covered areas.

Annealing Point - The temperature at which internal stresses in glass are significantly reduced. In the annealing operation, glass is gradually cooled from above the annealing point temperature to below the strain point temperature. This slow cooling relieves residual thermal stresses that would develop if the glass were allowed to cool in an uncontrolled manner.

Annealing - The process of slowly cooking a completed object in the furnace. The furnace is called an annealer or a Lehr. This is an integral part of glassmaking because the glass will be highly strained if it reaches room temperature too quickly and may break.

Antique glass - Glass with an uneven surface texture and bubbles inside produced using antique methods in order to obtain the appearance of glass made before the development of industrial processes. It may be drawn or produced from mouth-blown cylinders.

Art Glass - (1) Several types of glass with newly developed surface textures, shaded color, or casting, made in the United States from about 1870 and in Europe between about 1880-1900; (2) more generally, any ornamental glasswork made since the mid-19th century.

At-The-Fire - The process of reheating a blown glass object at the glory hole during manufacture, to permit further inflation and/or manipulation with tools.

Batch - The mixed raw materials used in manufacturing glass that have been blended and proportionally mixed for delivery to the glass furnace.

Bending - A process whereby the shaped glass article still in sheet form is placed on a stainless steel, sheet steel or cast iron mold coated with talc or powdered chalk. The temperature is increased until the glass sheet sinks in to the mold.

Bits - Pieces of molten glass snipped off a blowpipe or punty rod and applied hot to a glass form.

Blank Mold - The metal mold in which the parison is formed.

Blank - Usually refers to a glass parison that is formed during the first step of glass molding. The piece is then transferred to a lamp worker or glass blower for final shape configuration.

Blanks - The mold parts used in all glass container machines for preliminary formation of glass in preparation for the most efficient completion of glass containers in the finish molds where bottles are blown. The blank forms the parison. The parison itself is at times referred to as the blank.

Blister - A gaseous inclusion or bubble in the glass.

Blobbing - The technique of decorating hot glass by dropping onto the surface blobs of molten glass, usually of a different color or colors.

Block - A block of wood hollowed out to form a hemispherical recess. After it has been dipped in water to reduce charring and to create a "cushion" of steam, the block is used to form the gather into a sphere, prior to inflation.

Blowing - The technique of forming an object by inflating a glob of molten glass gathered on the end of the blowpipe. The gaffer blows through the tube, slightly inflating the glob, 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.

Borosilicate Glass - A high silicate glass with at least 5% boron oxide.

Bubbles - A pocket of gas trapped in glass during manufacture. The term is used for both bubbles introduced intentionally (also known air traps or beads) and bubbles trapped accidentally during the melting process. Very small bubbles are known as seeds.

Bullions - One of the few forms of flat glass still produced by the hand process. Bullions or "bull' eyes" are used for decorative window glass and are made by reheating and spinning out a bowl-shaped piece of glass.

Cable - A pattern resembling the twisted strands of a rope.

Came - A grove strip of lead or (rarely) another metal, generally with an H shaped cross section, used to join separate parts of glass window.

Cane - 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.

Caning - The removal of glass from the surface of an object by means of handheld tools.

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 formed.

Cast Glass - Glass produced by "casting', in other words by pouring molten glass into a mold or by heating glass already contained in the mold until the glass melts and assumes the shape of the mold.

Casting - The generic term for a wide variety of techniques used to form glass in a mold.

Cerium Oxide - The oxide of the rare earth, cerium, used alone or together with other substances as a polishing agent for glass.

Cobalt - A silvery-white magnetic metallic element, which, even in small quantities, gives a strong blue coloration to glass. It can be used as a decolorizor on its own for opal glasses. For flint, it may be used with selenium, manganese, nickle or cerium.

Cold Working - The collective term for the many techniques (such as engraving or cutting) used to alter or decorate glass when it is cold. Used to create texture or pattern into the surface.

Copper-Wheel Engraver - 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, 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.

Cords - Flaws in the material, which affects the artist's ability to work with the glass.

Core Forming - The technique of forming a vessel by trailing 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.

Core - The form to which molten glass is applied in order to make a core formed vessel.

Cracking Off - The process of detaching a glass object from a blowpipe or punty.

Crackle Glass - To produce the crackle effect, the parison is rolled in moist sawdust or covered with sand in order to give the surface a coarse finished. It is then submerged in water, causing the surface to crack, without destroying the glass. A fresh layer of glass is then added and reheated until the cracks fuse together slightly so that the glass maintains its stability.

Crown glass - Window glass blown into a crown or hollow globe that is flattened and cut before use. This is produced by reheating and spinning out a bow-shaped piece of glass (bullion) that causes the glass to extend into a flat disk by centrifugal force. The glass is then cut into the size required.

Dalle Glass - Colored glass produced in pot furnace and cast in molds to form plates. Dalle glass ("dalle" is French for "tile") is used in church and decorative glazing, as well as for furnishing such as door handles.

Dichroic - A type of manufacturing glass which has ability in two different ways. Color is transmitted through the glass and complimentary colors are reflected from the surface.

Electroplate - A process by which metal is adhered to glass by dipping it into an electrically charged solution. Encased Painting on Glass: The process of painting a glass object with glass paint, then subsequently re-heating the glass and gathering more hot glass over the surface, encasing the paint in 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 (muffin) kiln (about 500-700 degrees Fahrenheit). Sometimes, several rings are required to fuse the different colors of an elaborately enameled object.

Engraved - 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.

Engraving - The production of a design in glass by cutting into the glass surface. Engraving methods include copper wheel engraving, diamond, of tungsten point engraving, acid etching and sand blasting.

Etch - To create a design by cutting the surface of finished glass with a tool or treating it with acid.

Figured Glass - Also known as "patterned" or "ornamental" glass, figured glass is generally produced by the rolling process. The surfaces of the rollers used carry the pattern or design to be "imprinted" in the glass as it passes between them. The process gives the glass a texture surface on one side or both sides. The surface finish may be both decorative and functional. Apart from the huge variety of patterns possible, figured glass can also offer light dispersion and glare reduction characteristics.

Filigrana - The generic name for blown glass made with colorless, white, and sometimes colored cane. The filigrana style originated at Murano , Italy in the 16th century and spread through Europe .

Finished - The process of completing the forming or decorating of an object. Finishing may take the form of manipulating the object into its final shape while it is hot, of cracking off prior to annealing, or of grinding, cutting or polishing.

Fire-Resisting Glass - Flat glass with a wire inlay which helps retard shattering in the event of fire and thus delays the spread of smoke and flames. Such glazing is classified either as class G (which resists fire and prevents the spread of smoke and flames for a specific period of time) or class F (which has the characteristics of class G but also impedes the spreading of radiant heat for specific periods). New developments include pre-stressed wire-free borosilicate glass and double-glazing with the inner space filled with an intumescent material which acts as a heat shield.

Firing - The process of bringing a glass furnace up to its operational temperature and then maintaining the temperature.

Flameworking - The technique of forming objects from rods and tubes of glass that, when heated in a flame (gas-fueled torches), become soft and can be manipulated into the desired shape.

Flashing - The application of a very thin layer of contrasting color. This is achieved by dipping a gather of hot glass into a crucible containing hot glass of the second color.

Flat Glass - AII types of glass (rolled, float, plate, etc.) produced in a flat form, regardless of the method of production. Float process: A method for the production of high-quality sheet glass whereby a ribbon of molten is fed across a bath of heated liquid, usually molten tin, in a carefully controlled atmosphere. The UK firm Pilkington Brothers developed the process.

Flint - A glass color or lack of color. Flint is perfectly clear transparent glass, like window glass, used for all types of containers.

Founding - The initial phase of melting batch. The material must be heated to a temperature of about 2450 degrees Fahrenheit. This is followed by a maturing period, during which the molten glass cools to a working temperature of about 2000 degrees Fahrenheit.

Frit - Batch material that is melted with other materials and then ground into powder form before being added to the batch. Lead oxide, which can produce a harmful dust, may be melted with silica, for example, and then ground down as a lead silicate.

Fusing - (1) The process of rounding or melting the batch; (2) healing pieces of glass in a kiln or furnace until they bond; (3) heating enameled glasses until the enamel bonds with the surface of the object. Fusing glass-to-glass: Glasses of different compositions can be fused together for decorative purposes and also in the sealing of electric, medical and industrial components. The fusion temperature for soda-Iime glasses is generally between 760 and 820C. Particular attention must be paid to the thermal expansion coefficients of different glass types.

Gaffer - The master craftsman is charge of the team of hot workers.

Gather - (Noun) A mass if molten glass collected on the end of a blowpipe or punty. (Verb) to collect molten glass on the end of a tool.

Gathering Iron - A long, thin tool used to gather molten glass.

Glass - A homogeneous material with a random, liquid like molecular structure. The manufacturing process requires that the raw materials be heated to a temperature sufficient to produce a completely fused melt, which, when cooled rapidly, becomes rigid without crystallizing.

Glory Hole - A hole in the side of a glass furnace, used when reheating glass that is being fashioned or decorated. The glory hole is also used to fire-polish cast glass to remove imperfections remaining from the mold.

Glassblowing -The shaping of glass using air pressure.

Grall - A glassblowing technique wherein a thick "blank" or core form is blown, usually with two or more layers of color. The blank is then engraved, bringing out the underlying color much like a cameo. The engraved blank is subsequently reheated and blown to full shape, fusing the image into the surface.

Grinding - The removal of glass with abrasive or abrasive (grinding) wheels in order to shape, polish or otherwise finish both flat and hollow glass. Grinding process include milling, sawing, edging, and drilling.

Hard Glass - A glass with a high softening point or high viscosity (usually borosilicate).

Hydrofluoric Acid - A highly corrosive acid that attacks silicates such as glass. Purehydrofluoric acid dissolves glass, leaving a brilliant, acid-polished surface.

Incalmo - The process in glassblowing of joining two or more bubbles of hot glass together to create defined bands of color.

Intaglio - A method of engraving whereby the orientation is cut into the object and lies below the surface plane.

Kiln Cast - The use of a mold, usually plaster, filled with crushed glass, which is melted in a kiln to produce a solid glass form.

Kiln - A high-temperature electric oven, usually monitored by a computer, used for casting, fusing and slumping glass.

Laminated Glass - Laminated (or compound) glass consists of two or more sheets of glass with one or more viscous plastic layers "sandwiched" between the glass panes. The solid joining of the glass takes place in a pressurized vessel called an autoclave. In the autoclave, under simultaneous heating of the already processed layers of glass and special plastic, lamination occurs. When laminated safety glass breaks, the pieces remain attached to the internal plastic layer and the glass remains transparent.

Lampworking - Flame re-working of a blank or tubing cane, typically on a lathe.

Lehr - A long belt-fed, tunnel-shaped oven used to heat glass to the annealing point and then slowly cool it to room temperature to remove any residual thermal stresses in the glass. Can also be a large oven where glass is manually loaded and unloaded (batch lehr).

Linear Coefficient of Expansion - The fractional change in length of a piece of glass per degree change in temperature. The coefficient of expansion generally indicates the thermal endurance of the glass. Glasses with a low linear coefficient of expansion can be subjected to greater rapid temperature changes with less chance of fracture than glasses with a high coefficient of expansion. (Generally, Type I glasses have a lower COE than Type III ).

Lost Wax Casting - The object to be fashioned in glass is melded in wax and encased in clay or plaster that is heated. The wax melts or is "lost" , leaving a mold into which hot glass can then be poured. The mold must be broken in order to retrieve the cast object.

Marver - A smooth, flat surface, over which softened glass is rolled in order to smooth it or to consolidate applied decoration.

Melt - The fluid glass produced by melting a batch of raw materials.

Millefiori - Objects made from preformed elements placed in a mold and heated until they fuse. Millefiori is a Venetian term. The term "mosaic glass" is also accepted. Mold: A form normally made of wood or metal.

Mold-Blown - Glass formed into a shape by being blown into a mold usually made of wood, metal or plaster.

Mosaic Glass - Produced by a glassblower rolling the hot glass globe over a marble or iron plate covered with small pieces of colored glass. These pieces adhere to the surface of the globe. The object is then overlaid with clear glass before being finished.

Murrinni - Patterned glass cane cut into sections to form small disks used in decorating glass or constructing glass.

Off-Hand - Formed free hand on the end of a punty of blowpipe. No mold is used.

Optical Glass - The glass in lenses and prisms, in which homogeneity, refractive characteristics and the absence of defects such as seeds area of major importance. In many modern optical glasses, lead oxide has been replaced with barium oxide while lanthanum oxide is used for optical glass with low dispersion and a high refractive index.

Overlay - A thin layer of clear or colored glass on the outside of a piece.

Opal Glass - Glass that resembles an opal, being translucent and white, with a grayish or bluish tint.

Paradise Paint - A specially formulated glass paint, which will not loose color when, exposed to the intense heat of molten glass. Paradise paint is often used to decorate pieces created using encased painting or graal techniques. Patterned glass: see figure glass.

Pick-up Decoration - A technique whereby a hot parison is rolled in chips of glass, which are picked up, marvered, and inflated.

Plate Glass - Flat glass made by the casting or rolling of molten glass which is then mechanically ground and polished to produce a smooth and transparent sheet.

Pipe – A long hollow steel rod used in glass blowing. By blowing through the pipe, the glass is formed into the preliminary shape. Sometimes referred to as a “rod”.

Polishing Wheel - Traditionally made of wood or bristle and more recently of cork, polyurethane and bonded cloth, these discs are used in conjunction with abrasive pastes to polish glass surfaces. Felt wheels with material such as cerium oxide and other commercially produced powders are now widely used for fine polishing. In the polishing process, the wheel is rotated at speed by means of a motor and applied to the glass to be polished.

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

Pontil - The pontil, or punty, is a solid metal rod that is usually tipped with a wad of hot glass, and then applied to the base of a vessel to hold it during manufacture. This is called the "punty mark".

Pot - A fire clay container placed in the furnace in which the batch of glass, raw materials used to make glass, is held and melted. The glass worker gathers directly from the pot.

Punty – A solid metal rod that is usually tipped with a wad of hot glass, and then applied to the base of a vessel to hold it during manufacture. This is called the "punty mark".

Reticello - {Vetro a Reticello) A type of blown glass made with canes laid in a crisscross pattern for form a net.

Sand - The most common form of silica used in making glass.

Sandblasting - To blow or blast sand or Carborundum onto a piece of glass, which etches or blasts away layers of glass. Masking is used to create patters.

Sandblown - The process of blowing a bubble of hot glass into sand mold.

Sandcast - To ladle hot glass into a mold made of special casing sand.

Sar - A single piece of glass formed by fusing several canes or rods. A bar can be cut into slices, all with the same design, to be used as inlays or appliques, or making mosaic glass.

Satch - The mixture of raw material (often silica, soda or potash, and lime) that is melted in a pot or tank to make glass. Gullet is added to help the melting process.

Scavo - Corrosive chemical material added to the surface of hot glass, which gives a matte finish to the final piece.

Screen-Printing - A process for the decoration of glass whereby colored ink is forced by a flexible "squeegee" through a fine-mesh screen, or "mask", {traditionally made of silk, now also made of nylon, polyester and stainless steel) onto the glass surface. A separate mask is used for the application of each color. Considerable automation of the process has been developed, thus allowing extremely high printing speeds for even complex designs.

Scruffitto - Color is added to the surface of glass and then scratched away, so that an image appears in reverse.

Seeds - Minute bubbles of gas, usually occurring in groups.

Shard - A small fragment of glass. Colored shards can be melted into pieces for decoration.

Slump - To heat a sheet of glass in a mold until it is soft enough to assume the mold shape with out becoming molten.

Smalti - A soft, intensely colored Venetian glass that is chipped into squares for use in creating traditional mosaic.

Soda-Lime (or Soft) Glass - A glass with a substantial portion of lime in the formula.

Softening Point – The specific temperature in which glass is just barely able to maintain its shape and not flow like a liquid.

Softening Point. Temperature at which a thread or rod of glass rapidly deforms under its own weight.

Stippling - (1) The technique of tapping the surface of a glass objects with a pointed tool, often a diamond or tungsten carbide tip. Each tap produces a mark, and the decoration is composed of many hundreds and thousands of marks. (2) On lacy-pattern pressed glass, the stippling is part of the decoration of the mold.

Strain Point - The temperature at which thermal residual stresses become permanent upon cooling. Temperatures above the strain point will introduce permanent stresses that can cause or contribute to fracture. At temperatures below the strain point, the glass can be temporarily heated and cooled without introducing permanent stress. The strain point can be considered the maximum service temperature.

Studio Glass Movement - A movement that began in the United States in the 1960's and has spread allover the world. It is characterized by the proliferation of glass artist who are not affiliated with factories, but work with hot glass in their own studios. The emergence of independent glass artists was made possible by Harvey Littleton and Dominick Labino's developments in 1962 of a small furnace and easy-to-melt glass.

Threads - Thin strands of glass usually colored, which can be added to the glass in a variety of ways for different effects.

Tank - The furnace that melts the raw materials into molten glass. Temperatures in the tank vary depending on the glass type being melted, but are typically in excess of 1,200°C.

Temper - The degree of residual stress in annealed glass as measured using polarized light techniques.

Tolerance – The allowable variation from actual specifications permitted in the manufacturing operation.

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

Undercutting - The technique of decorating glass in high relief by cutting away part of the glass between the body of an object and its decoration.

Type I Glass – Containers made of Type I Borosilicate glass are generally used for preparations that are intended for parenteral administration. Highly resistant borosilicate glass.

Type II Glass – Treated soda lime glass.

Type III Glass – Soda lime glass.

Type NP Glass – General purpose soda lime glass.

Underlay - A thin layer of clear of colored glass on the inside of a piece. Weathering: Changes on the surface of glass caused by chemical reaction with the environment. Weathering usually involves the leaching of alkali form glass by water, leaving behind siliceous weathering products that are often laminar .

Weathering – The attack on glass surface by atmospheric elements.

Wheel Engraver - Wheel engraving process of decorating the surface of glass by the grinding action of a wheel, using disks or various size and materials (usually copper but sometimes stone). An abrasive in a grease or slurry is applied to a wheel, as the engraver holds the object against the underside of the rotating wheel.

Wrap - A strand of glass applied hot to a vessel.

Zanfirico - The process of heating up cut canes of glass (usually with an Interior spiral pattern) and gathering them onto a pipe to be blown into shape. Also know as filigrana. Formerly called latticino.