Glass Blowing Terminology



Annealing- is the uniform and controlled cooling of a finished piece of glass.  Without proper annealing the finished work may eventually crack or break.

 Annealing Temperature Range -is the temperature at which molecular stresses are relieved in the cooling process after heating the glass.

Bead Separator (also known as bead release) -is a thick liquid that is applied to a mandrel to keep the hot glass from sticking to the stainless steel.  A simple bead release is a mixture of alumina and high-fire clay with water.

Borosilicate Glass (also known as Hard Glass) -is a glass composed of boron and silica.  An example would be Pyrex, a brand name of this type of glass.

Cane- is a thin rod of pulled or twisted glass.

Cased Beads or Encased Beads- are composed of two or more fused layers of glass.  The final or outside layer of glass is usually clear or transparent.

Coefficient of Thermal Expansion or COE- is the linear measure of how much a material elongates within a given temperature change.

Cold-working- is mechanically altering the appearance of glass when it is cold.  Grinding, etching, cutting and faceting are examples of cold-working techniques.

Compatibility- refers to types of glass which have the same coefficient of expansion - COE.  When glass is heated it expands and when it is cooled it contracts.  The ability to contract at the same rate is essential.  When glass is incompatible breakage will usually occur.

Controller- controls the cooling, heating and maintaining of the temperature of a kiln.

Devitrification- occurs on the surface of some glass when crystals form due to the loss of the fluxing agent when over heated. The glass often takes on a matte or dull finish. Certain types and colors of glass are more susceptible to this than others, one particular shade of Moretti purple in particular, which is often referred to by beadmakers as “Evil Devitrifying Purple”, or, EDP.

Dichroic Glass- appears one color in reflected light and the complementary color in transmitted light.  The iridescent appearance is caused by a thick layer of metallic oxides. (di = two; chroic, chrome = color).

Drawn Beads- are cut from a hollow pulled tube.  The process usually refers to furnace glass.

Didymium Lenses- are used by lampworkers to protect the eye from infrared and ultraviolet radiation from hot glass and to eliminate the yellow sodium flare created when glass is worked in the flame.

Encased Bead – see Cased Bead.

Etching- is a surface finish that results in a matte or frosted appearance.  Hydrofluoric acid, sandblasting and tumbling are all methods used for etching.

Faceted Beads- have surfaces that are cut into a systematic arrangement of intersecting, flat planes.  Faceting accentuates the optical properties of glass by increasing its reflective qualities.

Fiber Blanket- is a thick insulating blanket made from non-asbestos fibers.  Some beads may be prevented from thermal shock by placing them between two layers of fiber blanket so that they can be annealed at a later time.

Filagran-a is a rod with a solid color core cased in a clear or transparent color.

Fiber Pape- is a high-temperature fiber material made in thin sheets.  It is used for mold making and other kiln forming processes.

Fire Polish- is to create a glassy finish on glass by the use of heat.

Flame Annealing- is a method of slowly cooling a bead in the outer reaches of the flame of the torch.

Flameworking- is the manipulation of glass by means of a torch.

Frit- is crushed glass of varying mesh sizes.

Fuming- is the process of melting or burning a metal or metallic salt onto the surface of a piece of glass.  The metal, often gold or silver, is heated within a flame until it vaporizes.  The vapor is then deposited onto the surface of the glass creating an iridescent glow.  Metallic vapors can be toxic.  Safety precautions should be taken when fuming.

Furnace-worked Beads- are beads that have been made with the use of a pot furnace and glory hole.  Traditional glassblowing techniques are often utilized in the production of these beads. Also known as Drawn Beads.

Fusing- is the process of heat bonding two or more pieces of glass together.  This can be done in a glory hole, kiln or torch.

Gather- is a glob of glass on the end of a punty or blowpipe.  In lampworking the gather is formed by melting the end or a rod and allowing more of the rod to be fed into the flame so that the molten area of the glass is increased.

Glass- is a non-crystalline material with the mechanical rigidity of a solid and the atomic qualities of a liquid.  Most glass is composed of silica, sodium oxide and a stabilizer such as calcium oxide.

Glass Enamels- are powdered glass applied to and bonded by heat to a heat resistant surface such as glass, fine silver, copper or pure gold.

Glory Hole- is a type of furnace used by glassblowers to re-heat glass while it is being formed.

Hard Glass – see Borosilicate Glass.

Kiln (also known as oven)- is a heated chamber used for the fusing, slumping, casting, or annealing of glass.  Kilns are typically powered with electricity.

Kiln Casting- is the forming of glass within a mold using a kiln as the heat source.

Kiln Wash-  is a liquid ceramic mixture that is applied to a surface to prevent the hot glass from fusing to that surface.  In beadmaking the term bead release is often used.

Lampworking- is a term derived from the original method of working glass with an oil lamp or Bunsen burner.  Today this technique is commonly referred to as Flameworking.

Lathe- is a machine on which a piece of glass is mechanically spun.  It is used by glassblowers as a third hand to aid in the forming of glass.

Latticino- is a decorative type of twisted glass cane.  The Italian word literally translates into “little milk-white strands” and referred to canes made with only clear and opaque white glass.  Today the term includes all color combinations of twisted cane.

Luster- is a decorative finish created by applying a metallic oxide to the surface of glass.

Mandrel- is a stainless steel rod used in beadmaking.

Mandrel Release – see Bead Release.

Mandrel Wound (also known as Wound Bead)- refers to beads that have been made on a mandrel.

Maria – Flattened disk made on the end of glass rod, or punty, to provide a wider surface for attaching a glass bundle.

Marver- is a surface, often metal, stone or graphite, on which hot glass is rolled to smooth or shape.

Metallic Foil or Leaf- is a paper thin sheet of metal applied to the surface of glass or encased as a decorative element.  Fine silver, 22k or 24k gold and palladium are metals most commonly used by beadmakers.

Millefiori- are a specific type of murrine which resemble a flower.  Translated from the Italian it literally means a thousand flowers.  Millefiori are slices of a mosaic cane that have been built up from concentric layers of glass.

Mold- is a form which is used to shape glass.  Typically molds for lampworking are made from metal, wood or graphite.  For kiln forming the molds are constructed from heat tolerant fiber paper or a plaster-like investment.

Murrina (singular)- is a slice of cane that has been made by composing different colors of glass to create an image.  The design will run the full length of the cane.  Murrine (plural) can be made using various hot and cold techniques.  The end result can depict faces, animals, numbers, letters and other non-linear images.

Oxidizing Flame- is a flame that has an excess of oxygen, causing the flame to be hotter, which could boil the glass..

Pate De Verre- literally translates from French as paste of glass.  Originally the term referred to the process of fusing thin layers of colored, powdered glass that had been painted onto the surface of a mold.  The mold would support the glass during firing and would later be removed to reveal the glass sculpture inside.  Today the term Pate De Verre is used more generally to include larger frit casting methods.

Pontil or Punty- is a metal or glass rod used to handle molten glass.

Pulling Points- is to heat, collapse and pull a section of tubing to create a long thin handle.

Premix Torch- is a torch that is constructed so that the gasses are mixed inside the torch.

Press Molding- consists of pressing hot glass into a form to achieve a desired shape.  Historically beads and glass cabochons, flat-backed pieces of glass set as stones, have been made using one and two part molds.

Pot Furnace- is a heated chamber which holds a crucible or container of molten glass.  Glassblowing furnaces are typically powered with gas.

Powder- is glass that has been ground to a fine, flour-like consistency.

Raking, Feathering, Trailing -are all decorative techniques of drawing softened threads of glass over the surface of a hot piece of glass.  Graphite or metal tools may be used to push and pull the threads of color to their desired position.

Reducing Flame- is a flame which is deficient in oxygen.  Using a reducing flame can steal oxygen from metal oxide colorants in the glass making it dull.

Rod- is a straight, round length of glass.

Sandblasting- is the technique of etching the surface of glass with sand projected by compressed air.

Scoring- is to scratch the surface of glass, creating a fracture point where the glass can be broken.

Soak or Soaking Time- is the length of time an object is held at the annealing temperature to remove the internal strain created by heating glass.

Soda-Lime or Soft Glass- is composed of silica, soda and a stabilizer such as calcium oxide.  Bullseye and Effetre (Moretti) are examples of this type of glass.

Softening Point- is the temperature where the glass will slump or deform under its own weight.

Strain Point- is the temperature below which, stress can neither be added nor subtracted from the glass. Below this temperature, the molecules of the glass are “frozen” in place.

Stringers- are thin spaghetti-like pieces of glass.  They are often used for surface decoration or in creating small details of design.

 Surface-Mix Torch is a torch that is constructed so that the gasses are mixed at the surface of the face plate of the torch.

Thermal Conductivity- is a measure of how quickly heat moves through a material.

Thermal Expansion- is the property of a material that when it is heated it's dimensions increase or expand.

Thermal Gradient- is a variation of different temperatures within the glass.

Thermal Shock- is the strain created by abruptly heating and cooling a piece of glass.  Glass can be thermal shocked when it is heated or cooled too fast and breakage will occur.

Torch- is a heat source used for lampworking.  A mixture of compressed oxygen and fuel gas (such as propane, natural or MAPP) is burned.

Tumbling- is the technique of abrading the surface of glass using an electronic tumbling machine and various metal or plastic media and chemical compounds.

Twistie- is a rod or stringer made by twisting two or more colors of glass together.

Working Range- is the temperature needed to form an object from glass.
Wound Bead – see Mandrel Wound.

Viscocity- is the measure of the amount of force needed to make a material flow.