Stained Glass Terminology & Definitions 

Stained glass is an old and historically significant form of glass art. While it has existed in some form since ancient times, stained glass reached its peak in the Middle Ages. 

Medieval stained glass decorated churches and taught illiterate churchgoers about important religious concepts. With both aesthetic and practical value, it is no wonder that hundreds of medieval churches and other buildings were decorated with ornate stained glass panels. 

Like any other type of art, stained glass has its own set of terminology. These words and concepts are important to know when studying and creating stained glass. 

Most of the terms provided here relate the historical methods of stained glass, and are therefore helpful for those wishing to better understand medieval stained glass. 

Abrasion

Scratching the surface of glass to remove one layer of color and reveal another. 

Acid etching

Removal of the surface layer to expose underlying glass using hydrofluoric acid. In medieval times, a tool was used. 

Badger

A broad brush used to spread glass paint evenly and easily. 

Cartoon

A full scale drawing of the intended glass design. Major artists like Hans Holbein sketched cartoons for various stained glass projects. 

Catherine window

Also known as a rose or wheel window, Catherine windows are symmetrical windows with radiating wheel spoke designs. Common in Gothic architecture. 

Cement

To make stained glass watertight. A mixture of chalk, linseed oil, and fixative applied to both sides of the stained glass piece and then cleaned. 

Cinquefoil

A window with a five-lobed shape. 

Corrosion

The deterioration of glass over time. Can include pitting, crusting, or unwanted iridescence. 

Diaper

A decorative pattern added to glass with paints. 

Glazier’s mark

Letters of numbers painted or scratched into the surface of a glass panel to identify, sort, or order pieces. 

Gothic

An architectural style popular in the Middle Ages. Developed from Romanesque architecture and identified by arches, vaulted ceilings, flying buttresses, and stained glass.

Grisaille

Monochrome painting on stained glass. Commonly silver enamel applied to clear glass. 

Lead

Metal used to assemble windows. Glass panels are surrounded by lead (or copper) and joined to other pieces. 

Panels

Pieces of stained glass windows, generally less than one meter square. Stained glass windows are made up of several panels. 

Quarry

Diamond shaped glass panes used as major design elements of background decoration. 

Rinceau

A foliated design used as background decoration.  

Roundel

A circular panel with a self-contained design. 

Trace lines

Strong, thick lines that emphasize the main design of a stained glass subject. 

Vidimus

Approved preliminary sketch that would become a cartoon. Several sketches were made before deciding on the vidimus and creating the cartoon. 

White glass

Clear or uncolored glass. Would have had a green or yellow hue in the Middle Ages.