Coloured glass is glass that has been tinted during manufacture by adding metallic oxides and other compounds to the molten batch. Different additives produce different colours: cobalt gives blue, copper produces green or turquoise, gold gives ruby or cranberry red, manganese creates purple or amethyst, uranium produces a yellow-green glass that glows under ultraviolet light, and iron gives greens and browns.
Coloured glass has been made since antiquity, but it became especially fashionable in Britain in the late eighteenth and nineteenth centuries. Bristol blue glass was popular for decanters, finger bowls and scent bottles, while the Victorian period saw a great expansion of colour, including cranberry, ruby, amethyst, green, vaseline and opaline glass. Cased or overlay glass combined layers of different colours, which could be cut back to reveal decorative patterns, and stained glass windows used coloured panels to dramatic effect. Antique coloured glass is collected for its beauty and variety, and its appeal is best seen when displayed against natural light.
