ANNEALING- The process of slowly cooling glass in an annealer to release any stress and strain created during the forming process. Proper annealing is critical in glassmaking, as glass that is allowed to cool too quickly will break as it cools or will be highly strained when it reaches room temperature and liable to break easily.
ASSISTANT- An individual assisting the gaffer make a piece.
BATCH- The mixture of raw materials (silica, soda, potash, lime) that is melted to make glass. UrbanGlass uses Spruce Pine batch.
BENCH- The bench is the heart of the hot shop work station. It consists of two parallel rails (to roll the blowpipes on), a tool table, and a seat where the artist sits and manipulates the glass.
BIT(S)- Small pieces of molten glass that are added to a piece to create color, handles, and stems.
BLANK- A cooled object that is manipulated and decorated while cool. Often it is reheated and blown or sculpted hot to produce a finished effect.
BLOCK- A wet wooden tool used to shape a hot gather in the glass before it's blown out.
BLOWING- The act of inflating a hot gather of glass through a blowpipe.
BLOWPIPE- An iron or steel tube, usually about five feet long, that is used for blowing glass. Blowpipes have a mouthpiece at one end and are usually flared at the other end with a shape that helps retain the gather.
BOROSILICATE GLASS- A type of glass that is dense, harder than soda or lead glass, and has a low co-efficiency of expansion (which allows it to withstand sudden changes in temperature). It is often used for sculpture flameworking because it passes from the molten to rigid state quickly.
CALIPER- Lockable tongs used to measure or reference a size or dimension of a glass piece.
CANE- A thin rod of glass, or a composite rod made up of different glass pieces bundled together and fused, and often pulled and/or pulled and twisted to form a design that is visible in cross section.
CARVING- The removal of glass from the surface of an object by means of hand-held tools or sandblasting.
CASTING- Generic term for a wide variety of techniques used to form glass in a mold, such as kiln casting and hot casting. Hot casting includes pouring molten glass into a mold or form. Kiln casting involves melting glass in a mold inside a kiln.
CHARGE- The act of filling the furnace with batch.
COLDWORKING- A term encompassing a variety of polishing, grinding, cutting and engraving techniques that are executed (usually in a Cold Shop) after glass objects have been formed, fully annealed and cooled. Many coldworking techniques include the use of rotary machinery fed with water and abrasives, or hand-held tools.
CORD- Accidental, colorless streaks in the glass caused by local differences in refractive indexes. Often caused by poor mixing of the [batch].
CORE FORMING- The technique of forming a vessel by winding, trailing or gathering molten glass around a core form supported by a steek rod or mandrel. After the forming process, the glass object is annealed, then removed from the mandrel and the core is scraped clean.
CRACKING OFF- The process of detaching the unwanted portion of the parison from the blowpipe and the intended rim.
CRUCIBLE- The cauldron (or bowl) that holds the glass inside the furnace.
CRYSTAL- Popular term for colorless lead glass that has a high refractive index and, consequently, is particularly brilliant. Often used to describe any fine glass tableware.
CULLET- Raw glass, or pieces of broken glass from a cooled melt. These scraps are generally intended for recycling.
CUTTING- The technique whereby glass is removed from the surface of an object. 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.
DEVITRIFICATION- A process during which glass becomes partly crystallized as it cools from the molten state. It can occur on the surface of a glass object as a result of unsuccessful annealing or accidental heating to a high temperature.
DICHROIC GLASS- Glass that is one color when seen by reflected light and another when light shines through it, sometimes due to the presence of minutes quantities of colloidal gold.
DIP MOLD/OPTIC MOLD- A cylindrical, tapered mold with an internal pattern. The mold is open at the top so that a [parison] can be dipped into it and then inflated.
ENGRAVING- A pattern or design that is cut into a glass surface, usually with a diamond-surfaced wheel on a lathe or bench grinder.
FINISHING- The procedure of concluding the shaping process.
FIRE POLISHING- Reintroducing the glass to heat in order to melt away any irregularities.
FIRING- The process of reheating an unfinished glass object while it is being worked.
FLAMEWORKING (lampworking)- The technique of forming objects from rods and tubes of glass that, when heated in a flame, become soft and can be manipulated into a desired shape. Historically, the source of the flame was an oil or paraffin lamp used with a foot-powered bellows, but today bench torches are used, which provide an intense,oxygenated natural gas or propane flame. This technique is also referred to as Lampworking.
FLASHING- Quickly placing the working glass into the glory hole to reheat the entire piece. This is meant to ensure that the glass will remain pliable and be kept safe from cracking.
FOOT- The base of an object; the part on which it rests.
FREE BLOWN (off-hand blown) GLASS- Glassware shaped solely by inflation with a blowpipe and manipulation with tools.
FRIT- Small pieces of colored glass that vary in size, and are used in the coloring process.
FURNACE- An enclosed structure for the production and retention of heat, used for melting glass batch and maintaining glass in a molten state.
FUSING- The process of heating the pieces of glass in a kiln until they bond. Over several hours, the temperature in the kiln is slowly brought up to fusing temperature, 1510° F (820° C), and then slowly cooled down again.
GAFFER- The master craftsman in charge of a chair, or team,of hot-glass workers and the entire production of a project.
GARAGE- A heating chamber used to hold and keep hot parts of objects that are intended to be assembled on the blowpipe while other parts are being made.
GATHER- The technique of winding a ball of molten glass (called a gather) from the furnace onto the end of a blow pipe or punty.
GATHERING IRON- A long, thin rod used to gather molten glass.
GLASS- A homogeneous material with a random, liquid (non-crystalline) molecular structure. The process requires that the raw materials (batch) be heated to a temperature high enough to produce a completely fused melt. The glass, when cooled rapidly, then becomes rigid without crystallizing.
GLASSBLOWING- The technique of forming an object by inflating molten glass gathered on a blowpipe. The glass is then manipulated and shaped by rolling it on a marver, swinging it, and shaping it with tools.
GLORY HOLE- A high-temperature, gas-fueled chamber used to reheat and maintain the temperature of glass pieces while being worked on. The glory hole contains an oxygenated gas flame that maintains a temperature of 2200° F.
GRAAL- A type of decorative glass developed by Orrefors of Sweden in 1916. The design is carved, engraved, or etched on a parison of colored glass, which is then reheated and cased in a thick layer of transparent glass of a different color, and inflated.
GRINDING- The technique of removing the surface of an object with a rotating wheel fed with an abrasive, or by some other means.
HOT-FORMED, HOT-WORKED- The generic term for glass that is manipulated while it is hot.
ICE GLASS- A decorative effect that causes the surface of the glass to resemble cracked ice, achieved by plunging the hot glass into cold water and withdrawing it quickly to create small fissures in the surface.
INCALMO- The technique of joining two or more sections of blown glass while hot.
INCLUSIONS- A collective term for bubbles, precious metal, glass particles, and other material that have been added to the internal layer of a glass object for decorative effect.
INTALGO- A method of engraving whereby the design is cut into the object and lies below the surface plane. The German name for this technique is Tiefschnitt.
JACKS- Large tong-like tools that are used to create score lines in the neck of a piece, among other things. It is the main tool used by glassblowers, and is also known as a borsella or pucellas.
KILN- An insulated, temperature-controlled chamber for heating and cooling glass.
KILN FORMING- The technique of fusing, shaping or otherwise altering glass utilizing the heat of a kiln.
LATHE CUTTING- The technique whereby a blank in the general shape of the finished object is mounted on a lathe and turned, while a tool fed with abrasive is held against the surface in order to polish it, modify the profile, or cut it.
LATTICINO- Threads of white or colored glass within the clear glass, sometimes lace-like in pattern.
LEAD GLASS- Glass that contains a high percentage of lead oxide (at least 20 percent of the batch). This kind of glass is relatively soft, and its refractive index gives a brilliance that may be exploited by covering the surface with polished wheel-cut facets.
LEHR, LEER- The oven used for annealing glass.
LIP WRAP- A thin trail of color that is wrapped around the lip/mouth of the piece.
MANDREL- A metal rod around which beads and other small obects can be formed.
MARVER- In French, marbre, meaning "marble". A flat sheet of steel used to shape and cool the glass.
MELT- The fluid glass produced by melting a batch of raw materials.
MILLEFIORI- An Italian glassmaking term meaning "one thousand flowers," used to describe Venetian mosaic glass objects.
MOIL- The unwanted top of a blown object. Removed after annealing, usually by cracking off.
MOSAIC GLASS- The technique of surface decoration or object making made up of smaller glass components, usually many small, adjoining pieces of glass that are then joined together through fusing or, in the case of tile mosaic, grouting.
MURRINE- From Latin murra, apparently a stone from which costly vessels (vasa murrina) were made.The English adjective "murrhine" and the Italian adjective murrino are sometimes applied to mosaic glass and similar objects. There is no evidence that confirms the popular view that the ancient Roman vasa murrina were made of glass. When used as a noun, murrina refers to a slice of a complex cane, while a murrino is an insert of multicolored glass embedded in a glass object.
NEON- An inert gas which, like some other gases, has the properties of high electrical conductivity and strong light-emissive power. Such gases may be introduced into evacuated glass tubes. Under these conditions, an electrical discharge causes the gas to emit light. Different gases emit different colors; for example, neon emits red, and xenon emits blue. Regardless of the gases employed, lighting of this type is known as neon lighting. The creation of neon-illuminated objects requires creation of glass tubes.
PARISON- A gather on the end of a blowpipe that is already inflated.
PATE DE VERRE- A French term meaning "glass paste," pate de verre is the technique of creating a solid form from a glass powder or frit. The "glass paste" is brushed or tamped into a mold and fused together in a kiln to form a solid object.
PINCERS- A glassworker's tool used for decorating objects by pinching the glass while it's hot.
POLISHING- The process of smoothing the surface of an object by holding it against a rotating wheel fed with a fine abrasive such as pumice or cerium oxide. Glass can be polished with hand held tools as well.
PONTIL/PUNTY- The pontil, also known as the punty, is a solid metal rod that is tipped with a small amount of hot glass and applied to the base of a vessel or object to hold it while the glass is formed. When the punty is removed it often leaves a scar on the base of the object called the pontil mark or punty mark, which is usually polished out of final art works.
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.
SANDBLASTING- The process of removing glass or imparting a matte finish by bombardment with fine grains of sand that are propelled by compressed air.
SCAVO- A process by which a rougher, matte finish is achieved, by adding a corrosive chemical to the surface of hot glass while it is cooling.
SEEDS- Small bubbled of gas that usually occur in groups.
SHEARS- A scissor-like tool that is used to cut, trim, and shape hot glass.
SILICA- Silicon dioxide, a mineral that is the main ingredient in glass. Sand is the most common form used in glassmaking.
SLUMPING- The technique of forming glass using a mold, heat and gravity in a kiln. Glass is shaped by falling into or over a slumping mold as the kiln heats the glass to a pliable state, referred to as slumping temperature, 1250° F (676° C).
SODA-LIME GLASS- Historically, the most common form of glass. It contains three major compounds in varying proportions, but usually silica (about 60—75%), soda (12-18%), and lime (5-12%). Soda-lime glasses are relatively light, and upon heating, they remain plastic and workable over a wide range of temperatures. They lend themselves, therefore, to elaborate manipulative techniques.
SOFFIETTA- A tool used to further inflate a vessel after it has been removed from the blowpipe and attached to the punty. The vessel is reheated, and the conical nozzle of the soffietta is inserted into its mouth so that the aperture is block and air can be blown in through the tube.
SOFT GLASS- A generic name for glass with a relatively high coefficient of expansion.
STAINED GLASS- The generic name for decorative windows made of pieces of colored glass fitted into canes and set in iron frames. In addition to glass colored by staining, glaziers use glass colored throughout by metallic oxide, glass colored by flashing, and glass decorated with enamel.
STAIN CRACKS- Fissures in a glass object caused by internal stress from inadequate annealing and/or accidental thermal shock.
STRIKING- The process of reheating glass after it has cooled, in order to develop the color or the opacifying agent which appears only within a limited range of temperatures.
STUDIO GLASS- A term used to describe unique or limited-edition glass objects that were designed and created in a studio instead of a factory.
STUDIO GLASS MOVEMENT- Art movement that began in the United States in the 1960s, characterized by the proliferation of glass artists who were not affiliated with factories, but worked with hot glass in their own private studios. The emergence of independent glass artists was made possible by the development of small furnaces and easy-to-melt glass.
TAGLIA- A square-ended knife used to shape or sculpt molten glass on the blowpipe.
THREADING- The process of winding a thin trail of glass around an object to create the appearance of parallel lines.
TOOL- General term that describes any tool used by glassworkers during the glassmaking process. Glassworker's tools include the blowpipe, pontil, gathering iron, jacks, shears, clapper, pallet, block, pincers, battledore, lipper, and crimper.
TRAIL- A strand of glass, roughly circular in section and drawn out from a gather, used to decorate the surface of a glass object.
VETRO A RETICELLO- An Italian term, meaning "glass with a small network." This blown glass technique utilizes glass canes laid in crisscross pattern to form a fine net, which may contain tiny trapped air bubbles.
VETRO A RETORTI- A type of glass made with canes that have been twisted to form a spiral pattern.
WHEEL ENGRAVING- The process of decorating the surface of the glass by grinding it against a wheel. The engraver holds the object against the underside of the rotating wheel to which disks of various sizes and materials and an abrasive in a grease or slurry have been applied.