Glossary of Terms


An amorphous solid, glass has a random molecular structure like a liquid even when it cools to a solid state. Made primarily of silica, other materials such as fluxes, stabilizers, and oxides are mixed into the base formula for glass to achieve desired properties such as heat tolerance, strength, or color. These materials are melted at high temperature and fuse together into a new material - glass!

Image Source: 


Hot Shop

Glassblowing - Inflating and shaping a gather (gob) of molten glass on the end of a blowpipe to the desired size and form. 

Hot Sculpting - Using tools to manipulate hot glass into identifiable shapes or abstract forms. 

Soloblowing - When a gaffer works without any assistants.

Moldblowing - When a molten glass bubble is blown into a negative space and takes on the new shape. Molds can be made of a range of materials, but are traditionally wood, cork, metal, graphite, or plaster. 

Gaffer - The person in charge of the blown glass piece. If working in a team, they are the lead person on the team. 

Assistant - The person helping the gaffer on the glassblowing team.

Furnace - An enclosed chamber used for melting the batch (raw glass), and keeping molten glass ready to use. The furnace at UrbanGlass stays on 24/7 at 2,150°F! 

Reheating Chamber - Where the glassblower reheats the glass after it has been gathered from the furnace, usually situated in front of the bench.

Annealer - Kiln (oven) used to slowly cool glass. 

Cane - Thin, colorful glass rods used to make decorative lines and patterns in blown/sculpted objects.

Murrine - Pulled glass cane that is fused together and cut into thin cross sections, revealing a pattern. 

Goblet - A cup or bowl that rests on a footed stem. A goblet usually requires a series of very fine, intricate parts to be joined together in careful sequence. 

Flame Shop

Flameworking - Forming objects from pre-made rods and tubes of glass that when heated in the flame of a torch become soft and shapeable by tools into desired forms.  

Torch - Tool emitting a controlled flame fueled by a mixture of gas and oxygen, used to melt the glass.

Soft Glass - Generic name for glass with a relatively low melting point and high COE (see other glass terms). It works well as furnace glass, but cannot handle rapid heating and cooling.

Borosilicate - Type of glass that withstands the shock of sudden changes in temperature (thermal shock), often used in scientific glass and cookware.

Rod - A monochrome or clear segment of glass, available in different diameters. 

Tube - Hollow, cylindrical sections of glass available in varying diameters, thicknesses and lengths.

Beadmaking - Winding molten glass around a mandrel to create a bead with a hole in its center that may be strung into beautiful jewelry or sculptural objects. 

Mandrel - Thin metal rods used in beadmaking.

Bead Release - Clay-like slurry used to coat the end of a mandrel, keeping hot glass from fusing directly to the metal. The finished bead can then be pulled free and the mandrel reused infinitely.

Vermiculite - Non-flammable insulation material, useful for slowly cooling hot glass without an annealer. 

Neon Shop

Neon Bending & Signmaking - The process of bending glass tubes according to a pattern, filling them with inert gasses, and introducing an electrical charge so the gasses emit light. Different gasses emit different colors. Regardless of the gasses employed, the finished product is called neon.

Electrode - A specially made, wired glass component fused to either end of the glass tube, which allows power to run through the tube and light it up. 

Transformer - An electrical component that adapts the power from a wall socket to make it suitable for illuminating neon tubes. 

Wiring Kit - Small package of wires and plastic parts used to connect a completed neon piece into a wall socket for power and illumination. 

Ribbon Burner - Torch with an expandable strip of flames that allows a long section of glass tubing to be heated at once, which is useful for bending arcs. 

Cross Fire - Torch with two heads facing each other, allowing a piece of glass to be heated from both sides at once.

Plasma - An ionized gas consisting of positive ions and free electrons in proportions resulting in more or less no overall electric charge, typically at low pressures (as in the upper atmosphere and in fluorescent lamps) or at very high temperatures (as in stars and nuclear fusion reactors). The fourth state of matter.

Cold Shop

Coldworking - The collective term for the many techniques used to shape, join or decorate glass with manual tools or machines when it is at room temperature (aka, solid). 

Lathe - Machining tool that spins wheels with various profiles to cut, sand, or engrave, using water to reduce abrasive friction. Lathe wheels are fixed on spindles and coated with an abrasive substance like diamonds to grind away the glass. 

Engraving - Cutting various marks into the surface of a glass object without going all the way through, either by holding it against the rotating wheel of a lathe, or with a hand-held engraver.

Sandblasting - The process of eroding or frosting the surface of glass by blasting it with fine grains of sand that are propelled by compressed air through a hand-held hose. 

Polishing - The multi-stage 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. 

Hand Lapping - Manually grinding or polishing glass against a flat glass plate with an abrasive grit called silicon-carbide. 

Lamination - Bonding flat facets of disparate pieces of glass together with glue.

Mold Shop & Kiln Room

Kilnforming - General term for fusing or shaping glass by heating it in a kiln, with or without a mold.

Kiln Casting - Melting glass into molds with the heat of a kiln.

Pate de Verre - Paste made from fine glass powder, a binder, and a flux (to facilitate melting). It typically has a grainy texture and is used to fill mold shapes. 

Lost Wax Casting - A sculpted wax model is encased in a plaster/silica mold then the wax is steamed out of the mold - or “lost” - creating a cavity. The cavity is then filled with glass and fired in the kiln, resulting in a glass object exactly like the wax model.

Kiln - Special oven used to melt, fuse, and slump glass at a controlled rate.

Plaster - Powdered material that when mixed with the right amount of water will become a liquid that will harden, making it great for moldmaking and casting. 

Silica - The most common component of sand, silica is the main ingredient used to make glass. Silica can be mixed with plaster to create high-temp molds for casting.

Billets - Thick glass tiles that are intended for glass casting, resulting in castings with few or no trapped air bubbles.

Frit - Crushed glass ranging in size from coarse granules to fine powder. 

Flat Shop

Glass Imagery - General term for the vast range of processes for applying imagery to glass including painting with enamels, applying decals, manipulating powders, and more.

Fusing - The process of heating separate pieces of glass in a kiln or furnace until they bond.

Slumping - Heating a piece of glass until it becomes soft enough to bend under its own weight over or into a mold, taking on the shape of the mold.

Mosaic - The process of cementing small glass pieces into place to form a larger picture, then grouting over the final image to seal the work. 

Stained Glass - Generic name for decorative windows made from pieces of colored glass joined together at the seams with copper foil and solder, or lead came. 

Copper Foil Method - This process was made famous by stained glass lamp shades designed by Louis Comfort Tiffany. Metallic foil is wrapped around pieces of glass and then paint with flux in preparation for soldering the pieces together. 

Solder - Metal wire, typically a mix of lead and tin, that is melted onto the edges of glass covered to bond the pieces together. 

Flux - Paste that lowers the melting temperature of another substance so that less heat/energy is required to melt it. 

Glass Cutter - Tool that scores a line on a piece of glass, creating a stress point along which it can be snapped apart. 

Lead Came - Channeling used in stained glass to make framing or structural lines.

Other General Terms

Amorphous Solid - Any noncrystalline solid in which the atoms and molecules are not organized in a definite lattice pattern.

Batch - The mixture of raw materials (often silica, soda or potash, and lime) that is melted in a pot or tank to make glass. It begins as an opaque dust and turns into clear glass once fully melted. 

Cullet - Pre-melted glass used to refill the furnace as the level of glass lowers with use.

Annealing - The process of slowly cooling a hot glass object to room temperature to remove any stress that causes breakage. Hot glass left out at room temperature will crack from thermal shock as it cools.

Coefficient of Expansion (COE) - How much a material expands and contracts in response to changes in temperature. Different glasses have different COEs. Other materials can be embedded in glass if they have the same COE and are therefore compatible. 

Obsidian - a naturally formed glass made from the rapid cooling of viscous lava from a volcano. 

Tempered Glass - Glass that has been heated and then rapidly cooled, causing it to hold tension, which makes it very resistant to breaking. When it does shatter, however, the high stress causes it to break into even, small bits rather than larger shards. 

Float Glass - Molten glass is floated on a bed of molten tin to create large, perfectly flat sheets. This glass is made in very large industrial furnaces and used in skyscrapers and windows.