Stained glass is made from many different kinds of sheet glass. Knowing the names used by makers and suppliers makes it much easier to read a catalogue, understand a quotation or work out what is in an old window. Most of the terms describe either how the glass was made or how it looks.
Mouth-blown and machine-made
Sheet glass falls into two broad groups. Mouth-blown glass is made by hand: a bubble is blown into a cylinder, cut open and flattened in a furnace. It has slight variations in thickness and small bubbles and ripples, and it catches the light unevenly. Machine-made glass is rolled in a continuous ribbon between rollers, and the surface texture can be pressed in. It is cheaper, more uniform and more consistent from sheet to sheet.
The main kinds
| Name | What it is | Typical use |
|---|---|---|
| Antique | Mouth-blown by the cylinder method. The name dates from the Gothic Revival, when makers rediscovered medieval-looking glass. Small bubbles and streaks (often called straw marks) give it life. | Church and fine domestic work, restoration |
| Cathedral | Machine-rolled transparent glass, smooth on one face, with a light texture on the other. | Economical coloured panels, repairs |
| Flashed | A thin layer of colour over a clear or coloured base. It allows rich colour in thin sections and can be abraded or etched through to show the base. | Ruby, blue and other strong colours; heraldic work |
| Streaky | Two or more colours combined in the sheet, in swirls or bands. Can be mouth-blown or rolled. | Skies, water, foliage, drapery |
| Opalescent | Milky glass, made with a white flash or opal in the melt. Light is partly scattered, so the glass looks creamy and shows depth. | Tiffany-style lamps and panels, copper foil work |
| Opaque (opak) | Dense glass that lets little or no light through. Used where a solid colour is wanted. | Lampshade bases, mosaic, backgrounds |
| Reamy | Mouth-blown glass left deliberately uneven, with thick waves and collapsed bubbles that give a distorted, hand-made surface. | Restoration, character work |
| Seedy | Glass containing many tiny bubbles, either left in on purpose or from the melt. | Older-looking glass |
| Rolled and textured | Machine-made sheet with a pattern pressed into one side: hammered, rippled, granite, reed, and many more. | Privacy glass, doors, bathrooms |
| German new antique | Machine-made sheet with deliberate streaks and ripples to imitate the mouth-blown look. | Budget imitation of antique glass |
| Iridized | Glass with a thin metallic oxide coating that gives a shimmer. | Decorative accents |
| Fusible glass | Glass sold as tested compatible for kiln work, graded by COE (usually 90 or 96). | Fused and kiln formed glass |
Some of these names overlap. A flashed sheet can also be streaky, and an antique glass can be reamy. Suppliers often use slightly different terms for the same thing, so a sample is worth more than a description.
Colour in the glass and on the glass
In pot-metal glass the colour is in the glass itself, produced by metal oxides added to the melt. Flashed glass has colour only on one face. Painted and stained work adds colour or detail afterward and is fixed by firing; see how painted and silver stained glass is fired.
Where the glass comes from
Sheet glass for stained glass work is made by a small number of specialist makers, mainly in Germany, the United States and Britain.
- Germany. Mouth-blown antique glass, with the batch melted for about 14 hours at around 1450 °C. It is known for antique glass, genuine rondels, crown bullions and restoration glass.
- United States. Tested compatible fusing glass in COE 90 and 96, a wide range of sheet colours, sheet popular for copper foil work, and textured and coloured sheet.
- United Kingdom. Float and patterned glass. The float process, invented in the 1950s, underlies almost all modern clear window glass.
For the firing side of these glasses see firing temperatures and schedules for fused and kiln formed glass. Colour and compatibility vary, so test any glass before relying on it.
Choosing glass
- For a window that will be looked at closely and lit from behind, antique or flashed glass gives the most life.
- For privacy, choose a texture and test it in place. Some textures give more privacy than others.
- For copper foil work, opalescent and cathedral are the usual choices.
- For fusing, buy glass that is sold as tested compatible, and do not mix systems.
- Where the glass will be in direct sun or close to a heat source, thin ruby and some flashed glass can behave differently from other colours. Ask the supplier.
Related pages
- Glass Types
- How window glass was made
- Roundels and bullseyes
- Copper foil stained glass
- How to read a church window
- Glass Glossary