The process of heating a glass object to release the strain introduced in the forming process.

The relative content of oxygen and fuel in a flame or kiln. Atmosphere that is rich in fuel particles will affect glass one way (reduction) while an atmosphere that has a high proportion of oxygen will affect it differently (oxidation). Usually these affects are greatest on the metallic oxides used to color glass.

The working area of the glassblower or lampworker.

Blow Hose
A neoprene tube attached to a swivel with a mouthpiece at the other end. It is used to enable the flameworker to blow into his bubble while he works it in the flame.

The heat source of the flameworker. It usually runs on gas and oxygen or air. It consists of a head that contains many orifices to distribute and direct the flame, a body where the gas is passed up to the head, and a valve assembly where the proportions of the gas/oxygen mix and volume are controlled.

The application of one layer of glass over another, usually to achieve a layered effect for graal or cameo glass.

Coefficient of Expansion. The relative amount that a material will expand when heated.

Different glasses that have the same COE are said to be compatible. This means that they can be joined together while hot without breaking apart when cool.

Cracking off
The technique of breaking off the punti or rod that has been used as a handle during the forming process.

The term literally means “un-glass” and means just that. Under certain adverse conditions the elements at the surface of glass can break down and leave a white powdery-looking deposit. Sometimes devitrification can be eliminated by reheating, but often it cannot and it must be removed by acid-polishing.

Glass that has been coated with a thin layer of metallic oxide. Dichroic coatings transmit certain wavelengths of light while reflecting others, creating an interference effect similar to iridescence.

A violet-colored glass that has the property of being able to filter out the frequency of light given off by glass as it is heated in an oxidizing atmosphere. This bright light is called sodium flare and can be harmful to the glassblower’s or flameworker’s eyes so didymium glass is used to make protective eyewear for hot glass artists.

The technique of pulling a piece of hot glass to make it narrower.

A flameworking technique where the finished piece is reheated in a bushy, relatively cool flame to relax the stresses built up in it during the construction process. This is usually used only on small pieces and is generally regarded as a temporary measure for work that is to be properly annealed later on.

Any technique where the flame is used to burn apart two pieces of rod or tubing.

Also known as lampworking or lamp-blowing. The technique of heating, melting and forming glass rods and tubes using a flame generated by a burner or torch.


Ground up bits of colored glass varying in consistency from fine sand-like particles to coarse chunks. It is used as an applied decoration.

The technique of coating a rod of glass with a metal such as silver or gold and then placing the coated rod in the flame while holding the piece to be decorated jut just behind it. The metal is vaporized and the resulting fumes condense on the relatively cool surface of the piece.

Any mass of molten glass collected on the end of a punti or rod.

An amorphous, homogeneous material with a random, liquid-like molecular structure formed by heating the raw materials to a temperature sufficient to completely fuse them into a consistent material that, when cooled, becomes rigid without crystallizing.

A crystalline form of carbon, commonly used in glassworking tools because it does not burn or stick to hot glass.


Hard Glass
A common name for borosilicate glass. It has a COE of approximately 33.

A high-temperature electric oven used for annealing, fusing or casting glass.

A device that turns glass tubes at a consistent rate so that large pieces can be easily formed into other shapes. The use of a lathe frees the hands so that tools can be more efficiently utilized.

Melting point
The temperature below which glass acts as a solid and above which it can be shaped.

A form, usually made of clay, metal, or wood, that is used for shaping glass.

Optic mold
A open, cone-shaped mold with ridges on the inside that will impart a pattern on the surface of a gather or bubble that is inserted into it when hot.

An atmosphere that is rich in oxygen and contains very little uncombusted gas. Oxidizing atmospheres ten to affect colored glass that contains metallic oxides in a different manner than reducing atmospheres.

A common tool, usually made of graphite, used for forming hot glass.

A section of tubing prepared for flameworking. It consists of a specific length of full diameter tube with a tapered handle on each end formed when the section is drawn off the original tube. The tapered handles are also called “points”, and can be opened to allow the flameworker to blow into the tube to form a bubble.

Pontil, punti
A metal rod used by glassblowers to make small gathers or to provide a handle for an object while it is being made. Flameworkers use glass rods for puntis.

Finely ground glass.

The process of heating a glass piece from room temperature to a state sufficient to prevent serious shock when plunged into a flame. This can either be done in a kiln or in the backwash of a flame.

Pre-mix burner
Any burner that mixes the gases inside the body of the burner prior to ignition.

A tool, usually made of graphite, that a flameworker used to help form shaped form tubing.

An atmosphere that contains a large quantity of uncombusted fuel that can cause the oxygen molecules contained in the metallic oxides that color the glass to react. This can cause a metallic deposit to appear on the surface of the glass.

A device for controlling the pressure of gas within a contained system.

A length of solid glass of a consistent diameter.

A tool used to trim off ragged edges or unwanted bits of glass.

Holding a piece of glass in the annealing oven at a particular temperature to assure proper annealing.

Sodium flare
A bright flame resulting from the reaction of an oxygen-rich flame and the surface of glass containing sodium. It is protection from this that is the main purpose of didymium glasses.

Glass that changes color when re-heated is said to “strike”. The most dramatic example of this are the borosilicate colors in the ruby family that strike from a clear to deep red simply upon reheating.

A small metal attachment for plastic tubing used in blowhoses. This allows a flameworker to attach a blowhose to the end of a tube or point so that he can blow into the tube while he rotates it in the flame.

Thermal shock
The strain created by suddenly heating or cooling a piece of glass.

The working end of a burner that distributes the gases just prior to ignition. Tips are available in different shapes and sizes.

Glass that has been manufactured in a hollow form instead of solid rods. Tubing is used by flameworkers to make bubbles instead of gathering glass on a blowpipe.

An insulating material to prevent glass from cooling too quickly, prior to annea