Annealing - The process of slow cooling heated glass through the annealing zone to prevent the presence of internal stress.

Annealing Point - The most efficient temperature at which to anneal a particular glass.

Annealing Zone - The temperature range starting at the softening point and ending at the strain point. Generally located between 1100°F and 600°F (593°C and 316°C), depending on the chemical makeup of the particular glass.

Blank - A solid bottom layer of glass on which other pieces of glass are positioned prior to fusing.

Burn Out - The process of pre-firing a mold or material in a vented kiln to remove, with heat, any unwanted contaminants.

Casting - The process of pouring molten glass into a mold

Coefficient of Expansion (COE) - The measured expansion of heated glass based on the percentage of change of a glass rod heated one degree centigrade.

Combing - An activity in which glass that is heated to a liquid state is manipulated by pulling or "combing" a blunt point through the surface. Also used in glass blowing.

Compatibility - The absence of stress when different glasses are fused together. Glass that have the same or similar COE's are said to be compatible.

Crucible - A high temperature, pot-shaped container used to melt glass in furnaces or kilns.

Devitrification - A crystalline growth that appears as a scum or matte finish on the surface of some glasses when heated to fusing temperatures.

Fiber Paper - A thin, blanket type of ceramic fiber used in fusing for molds and kiln shelf protection.

Firing Profile - a.k.a. Firing Schedule - The entire collection of heating rates, set point temperatures and soak times associated with a particular firing.

Fire Polish - Heating glass to the point where the surface has a glossy, wet appearance. A technique used to retain a shiny surface to glass after it has been ground or sandblasted.

Flash Glass - A sheet of glass composed of a base layer with a thin contrasting layer of another color flashed or fused to the surface.

Frit - Small granules of glass ranging from fine powder to rock-salt size.

Frit casting - A process in which a mold filled with frit is heated to the point where the frit fuses into a solid mass.

Full Fuse - Melting two or more pieces of glass into one single piece of glass. At full fuse the surface is without texture.

Furniture - A collective term for the various posts and shelving used to support and separate the glass within the kiln chamber.

Fuse - The process of heat bonding glass together.

Glass Separator - A protective coating used to keep glass from sticking to the kiln floor and shelves.

Kiln Formed - Glass that is altered, fused, shaped or textured by the heat of a kiln.

Laminate - To heat bond glass to the point of just sticking together.

Lamp Work - any glass working technique done using the direct flame of a torch.

Mold - Any form made of a refractory material in which glass can be shaped by slumping into or over.

Pate'-de-verre - A frit casting technique; a paste of frit is placed in a mold and heated to the point where the individual granules fuse into a solid mass.

Peep Hole - Small hole(s) in a kiln designed for viewing the contents of the kiln chamber.

Pyrometer - The pyrometer is a meter that indicates high temperatures. In order to work, a pyrometer must have a thermocouple (temperature sensor) connected to it.

Refractory - Any material that will not bend, warp, deform or explode at a specific high temperature.

Sagging - When heated glass starts to soften, it slumps and sags under its own weight.

Slump - A Technique used to form glass using a mold, heat and gravity.

Soak - Holding glass at a particular temperature for a given period of time.

Softening Point - A term used to express the exact point at which unsupported glass, when heated, starts to soften and bend.

Stone - Small impurities in glass, such as a particle of furnace material.

Strain Point - The lowest annealing temperature. Below the strain point any stress in glass is permanent.

Stress - A force creating tension and compression within glass that could cause unwanted breakage. Internal stress can be caused by poor annealing or fusing of incompatible glass.

Strike - When glass changes color during a heating cycle due to the oxidation atmosphere of the kiln.

Thermal Shock - Glass breakage caused by rapid or uneven heating or cooling.

Thermocouple - The temperature sensing probe of a pyrometer. It's inserted into the kiln chamber to measure temperature.