A glossary of stained glass terms

The process of removing the surface layer from flashed glass to expose the underlying glass. This is achieved today by using hydrofluoric acid. In the medieval period a tool was used.

Antique glass
Mouth- blown handmade glass. (See Glass below)

A set of metal bars (wrought iron, aluminium, copper, brass) fixed into the masonry and designed to hold the panels of a stained-glass window.

Badger (badger-hair blender)
A broad, round or rectangular brush, traditionally made out of badger’s hair and used to spread the glass paint into an even matt.

The thick knot of glass at the centre of the crown or blown sheet left by the blowing iron.

Came or Calme (from the Latin calamus, meaning reed)
From the Latin calamus, meaning reed, H-shaped strips of lead used to assemble the pieces of glass. It is composed of a central part, called the heart or core, with leaves or flanges that covering the edges of the glass. Originally cast in moulds, in later times lead calmes have been extruded through a lead mill.

The full-sized drawing of a stained- glass window which shows the exact size and shape of all the pieces of glass, their colour, the sizes of the lead and the support system required to glaze the window.

Used to make a panel completely watertight once the window has been leaded together. Made from a mixture of whiting (powdered and washed white chalk), linseed oil and fixative, it is spread over both sides of the glass with a brush. The glass is subsequently cleaned with sawdust or whiting that soaks up any surplus cement.

Copper foiling
Individual pieces of glass are surrounded by copper tape, laid edge to edge and soldered along the join.

A disc of mouth-blown glass. Pieces blown by this method are recognisable by the concentric striations that result from the spinning of the crown during its manufacture.

A structural glass window/wall which uses thick slabs of cast glass that are cut or broken and cemented into a panel using an epoxy adhesive or cement matrix.

The artist’s original design of a stained-glass window, generally sketched out in a ratio of 1 to 10. The design is used as the basis for the full-size cartoon and is usually coloured. Historically it was called a @italic:vidimus.

A powder of coloured pot metal glass frit (a mixture of silica and fluxes) that can be diluted and used for painting many colours on glass. It is fixed by firing at temperatures between 550ºC and 750ºC.

Flashed glass
A base sheet of glass, usually white, on which is overlaid a thin ‘flash’ layer of coloured glass. The coloured layer can be ground away to reveal the clear or white glass underneath.

The action of taking a ball of molten glass, known as the ‘parison’ or gather, in order to blow it.

In the case of stained glass, the glass is blown and manipulated into a muff, crown or slab bottle.

Glass paint (vitreous paint)
A mixture of finely ground glass, iron or copper oxide, and a flux, applied to the glass and fired which to produces a brownish- black vitreous paint.

Furnishing or fitting windows (or other openings) with glass. This work is usually carried out by a glazier.

From the French word gris, meaning grey. A delicate pattern, usually of foliage, is painted onto white quarries that are then made up into geometric windows using very little coloured glass.

A method of shaping the edges of glass pieces to the right size using a metal tool known as a grozing iron.

Lead line
The line produced on a full-size drawing of a window to indicate the position of the lead calmes.

The web or matrix of lead calmes which hold together pieces of glass in a leaded window.

A single window opening (usually vertical). Gothic windows are made of several lights (or lancets).

A light, even wash of glass paint applied to glass to soften and control the light. Highlighted areas can be created by removing areas of the paint before firing.

Medallion window
A window which includes an arrangement of several narrative scenes enclosed in geometrical shaped borders.

A cylinder of blown glass, cut off at both ends then flattened to form a glass plate.

An element of a stained-glass window, generally no more than 1m square. A single window is, as a rule, made up of several panels.

Two or more pieces of glass laid one behind the other and leaded together to achieve special effects.

Pot metal
Glass that is coloured throughout, when molten, by the addition of one or more metallic oxides.

From the French word carré meaning square. They are usually square or diamond- shaped. They are often used in multiples to make up whole windows, or as a decorative background.

Rose window
A large circular window opening, usually divided by stone mullions, most often composed of stained- glass panels radiating from the centre.

A small panel of stained glass, generally circular, depicting a religious or secular subject.

Saddle (or tie) bar
A metal bar fitted across the window opening to support the window and to prevent sagging and flexing.

A soluble pigment usually prepared from haematite, which takes on a rose tint on firing.

Silver stain (or yellow stain)
A stain produced by applying a silver-compound solution to the surface of the glass. When fired, the stain turns yellow, ranging from a pale lemon hue to deep orange. It is nearly always found on the exterior face of the glass.

A piece of glass cut from a square bottle. Made from around 1890 until the 1940s, slab glass is irregular in thickness and intensity of colour. In windows it produces a jewel-like effect.

A spot of molten tin is positioned at the junction of two calmes in order to fix them together. A fatty substance called tallow is used to permit the solder to flow freely over the lead.

This is achieved by scratching away the paint, when it is wet or dry, by means of a needle, brush handle, etc. This allows for the creation of small patterns or for lightening the paint.

Tracery lights
Tracery lights are the small, often ornate, openings at the top of a window.

The first outlines painted onto the glass to delineate the design. Long, fine brushes are used to create a smooth, straight or curved lines.

A thin layer of glass paint, sometimes barely discernible, which has the effect of modifying the translucency of glass.

White glass
In stained-glass terms this means clear, i.e., uncoloured, glass. Medieval ‘white’ glass was often greenish or yellowish in colour.


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