Glasswork Glossary

Some basic terms


Aventurine – (goldstone) Clear glass containing millions of tiny copper crystals which give the glass a golden sheen. It is used as a base material for beads, and for decorative elements on beads.

Aventurine Blue – (sparklie) Similar to goldstone, but it is made from a dark blue glass containing tiny metallic filings that sparkle.

Annealing – After glass has been worked with heat, it will have residual stress within from temperature differences. Annealing is the process of heating the glass very slowly to a set temperature determined by the make and type of glass. It is held at this heat for a soaking period, during which the glass relaxes all stress, but does not change shape, or slump. It is then cooled very slowly to room temperature. Small work can be successfully annealed with the torch at the time of completion.

Bending – This is one of the fundamentals of glassblowing, referring to shaping heated glass with mechanical force. With respect to bead making, very little force can be tolerated, but gravity certainly is used to influence the shape of a bead. There are several techniques used to manipulate glass that are forms of bending, such as raking.

Bullseye fusible glass – A brand of glass manufactured in the US originally for the stained glass trade. In recent years, they began controlling the mixes and testing their glass for compatibility. The standard COE of 90, is now used to compare many other brands of glass as “Bullseye compatible”. Moretti glass is NOT compatible with Bullseye glass.

Cane – Glass rod or cane, is produced by slowly and steadily drawing a piece of glass from a molten pot of raw glass, or by heating and drawing out a block of glass that can have complex patterns inside. The cane is cut to lengths, or in slices, for use in glassblowing.

Casing – Covering the entire surface of the work with glass, using clear glass on beads, and generally a neutral color on mosaic work.

C.O.E. – Stands for “coefficient of expansion” which is a measure of how much a material expands for each degree it is heated, expressed as 104 x 10-7/0C. The whole number value is generally used by itself when comparing different types of glass, such as COE 104 for Moretti, and COE 90 for Bullseye.

Cutting – The first of the seven fundamental steps in glassblowing is cutting. Glass is most often cut by the “scratch and break” method, but can also be cut in a torch flame, and with an abrasive saw blade.

Dichroic glass – This is glass which has been coated on one side with metal oxide layers. These oxides are vaporized and deposited on the glass surface in a vacuum chamber, by heating the metal oxides between 1,000 and 2,500 degrees Celsius. The thickness of each layer is precisely calculated within five millionths of an inch. By building up multiple layers of different oxides, a wide range of reflected and transmitted colors are produced. Dichroic means two color, and each piece of this glass will reflect two different colors, depending on the angle light strikes it. Because of the specialized manufacturing, this glass can cost ten times more than plain glass.

Drawn glass beads – In the manufacture of glass beads, drawn canes with a central hole are produced the raw material from which many nearly identical beads will be cut. They can be produced in great numbers in a short time, compared to wound glass beads which must be made one at a time. The cut pieces of cane are finished by flame polishing, or by tumbling with abrasives.

Drawing – An essential step in glassblowing, where hot glass is pulled to make a longer and thinner piece. For example, when making stringers from rod.

Eye beads – Beads made of any material that have circular or spotted decoration may be considered eye beads. They were considered to ward off evil, by always watching out for the owner.

Feathered bead – There are two traditional forms of this technique, the “feather” and the “festoon” pattern. Both begin by trailing a contrasting color of glass onto a base bead to form parallel lines. A tool called a rake is used to drag the glass in a perpendicular direction, often referred to as “combing”. In the festoon, all combing is in one direction, while the feather alternates direction.

Filigrana – A clear cased glass rod with a colored core.

Frit – Granulated colored class, sometimes referred to as crumb glass. Hot glass is rolled in frit to create the effect of small dots of color. A single color can be used at a time, or mixed colors applied to form a pattern of spots.

Fusing – Fusing is the joining of glass while in it’s molten state. It is what happens to each gather of glass added to the piece being worked, a fundamental step in all glassblowing. It also is used to describe work done in a kiln or an oven where the pieces of glass are allowed to fuse together while hot.

Gathering – Another fundamental step in glassblowing, molten glass must be accumulated in the proper amount and location, referred to as gathering. The glass rod when heated in the flame will form a “gather” at the tip as it is rotated and softens.

Hard glass – (borosilicate glass) A heat resistant glass made under the brand names “Pyrex”, “Kimax”, and “Duran”. Boron oxide is added to the glass mix, reducing the COE to 33, and making it react far less to thermal changes. This makes it usable in the kitchen oven. Most glass figurines, ships, and sculptural pieces, are made of hard glass because of it’s tolerance to some parts cooling, while other areas are being worked in a flame. It is called hard glass because it retains it’s shape when heated, and does not flow or soften as readily as soft glass.

Lampwork – A form of glassblowing where the glass is heated over a flame. Originally from the Middle Ages, the term lampwork referred to oil lamps with a blowpipe directed into the flame to increase the heat generated. Today, modern torches use propane, natural gas, or hydrogen mixed with compressed air or pure oxygen to generate the intense heat required.

Latticino – The twisted canes of multi colored glass, cased in clear, are called latticino. In the basic design, the colored glass will look like a flat ribbon twirling inside the clear glass, but may also be many thin strips of color which spiral lengthwise.

Lusters – These are colors and metals like gold, which are painted on the surface, and then fired in a kiln to leave a permanent decoration.

Marvering – To shape heated glass into a cylinder, it is rolled over a flat marble, stone, or cast iron surface called a “marver”, and the process is called marvering. Most bead makers today use a graphite plate or hand held paddle.

Moretti – A brand of soft glass from Italy, that comes in many colors both transparent and opaque that is generally compatible for fusing together. The company has a 500 year history of glass manufacture, and countless beads have been produced with this glass throughout those years. The C.O.E. of Moretti glass is 104 x 10-7 /degrees Celsius, except the Alabaster colors which vary, and are not totally compatible. The glass is heated to 1706F when fluid, and solidifies when cooled to 1202F. The annealing temperature is 968F

Mosaic glass – (millefiori) In glassmaking, pieces of colored glass are assembled and fused into bundles with patterns, and both the glass units and finished work made from it are referred to as mosaic glass. Millefiori, meaning “thousand flowers”, is the best known type. Other designs are “stratified”, “ribbon”, and “filigree”. Mosaic beads are made from one or more mosaic components.

Murrini – Glass is bundled, fused, and pulled into cane similar to mosaic glass, but the goal is to produce a picture in a cross section of the finished glass cane. The image can be anything from a face to a fish or even words. Components such as eyes and lips, can be produced first, and incorporated in the final design. Each step of assembling pieces and pulling it out, reduces the size of the image, while retaining the detail. The finished murrini is sliced into thin chips that are then incorporated into a bead.

Polychrome – Meaning more than one color, in the context of glass beads, polychrome identifies individually created beads decorated by hand with several colors of glass.

Punty – A temporary handle attached to the glass piece in work where a “cold touch” of glass to glass to glass will break off easily when the piece is finished.

Rake – See Feathered bead. A pointed metal hook with a handle.

Soft Glass – (sodalime glass) Glass is composed of quartz sand (silica, silicon dioxide, SiO2) soda (sodium carbonate Na2CO3 or sodium oxide Na2O) quicklime (calcium oxide CaO) and other oxides added for clarity or coloring. The glass used in most of our beads is a soft glass, referring to the relatively low temperature that it is worked and how fluid it gets. The soda acts to lower the melting point of silica and was originally produced from the ashes of seaweed and certain salt water tolerant plants. Lime is added to strengthen the glass. In some areas potash (potassium carbonate K2CO3) was substituted for soda which is produced from wood ash. Historically, glass produced in factories varied depending on the local materials available.

Stringer – Glass rod of perhaps 2 mm or less diameter, that is used to add detailed decoration.

Tooling – Shaping hot glass into a desired form using a tool, such as pliers, mashers, or patterned stamps to make an impression.

Wound glass – Molten glass is wound around a mandrel like thread on a spool, forming a bead.