Cathedral Glass

Describes transparent glass that is monochromatic—i.e., single color sheet glass, with smooth or textured surfaces.

Copper Foil

Thin, narrow strips of adhesive-backed copper tape used to wrap the edges of glass pieces that have been cut to fit a pattern. Once wrapped, solder is applied, bonding the glass pieces together. Assembling a stained glass project in this manner is called the "copper foil technique." Louis Tiffany is credited with its development.

Iridescent

Surface treatment in which a layer of metallic oxide is bonded to the hot glass surface just after sheet-forming, resulting in a colorful, shimmering effect.

Opal or Opalescent

Said of any glass into which a material has been introduced at the raw materials stage (usually fluorine or phosphorus) which causes a degree of crystallization to occur, and creates opacity in the glass. Reflected light is colorless, therefore white. The degree of opacity (and "whiteness") is variable depending upon composition and temperatures used in the manufacturing process. Commonly then, white glass is called "opal."

• Solid Color Opalescent Glass: Glass which is both colored and crystallized, creating a single color sheet, more opaque than a cathedral. Sometimes called "opaque" glass.
• Mixed Opalescent Glass: White glass (opal) mixed with one or more other colors to create a variegated, multi-colored sheet. Light transmission varies with composition. Also called "variegated opalescent," sometimes "streaky."

Seedy Glass

Glass in which air bubbles are entrapped. Air or gas is injected into the molten glass prior to forming the sheet

Stained Glass

Commonly used to describe any colored flat glass or any object made of such glass joined by metal strips. The term originally applied to colored or clear flat glass cut to fit an artist's design, on which details were painted in pigment with a brush. The glass pieces were then heated in a kiln or oven to bond the pigment to the glass surface. This firing makes the painted detail as durable and permanent as the glass itself. Most religious windows from medieval times until this century were executed in this manner, and so the term came to be used first for any architectural application, and then for any design in colored flat glass. It is now universally accepted as a convenient general term to define the art, the craft, and the industry.

Streaky Glass

Two or more cathedral glasses mixed together to create a multi-colored glass sheet. Some use this term also to describe Mixed Opalescent glass as defined above.

Textured Glasses

• Rolled textures: In rolled glasses (see definitions below), one of the forming rolls is embossed with a texture that is imprinted on the glass as the sheet is formed. This produces glass smooth on one side and textured on the other. Common examples are "hammered," "granite," and "muffle."
• Natural textures: any textural effect created without mechanical influence or embossed rolls. Includes Baroque and Waterglass®.
• Cold glass textures: this category includes glue chipping, etching, sand blasting, and any other surface treatment performed on the cold glass sheet at room temperature.

Waterglass®

A Spectrum Glass exclusive. A natural surface texture created by stretching the hot glass sheet while it is still in a malleable state. The result is gentle, rolling waves that resemble the surface of a lake or stream.

Wispy

A Spectrum Glass innovation. Mixed opalescent glass with only thin wisps of white, like lazy cloud trails.