Layered glass is glass made from two or more fused layers of different colours, which may then be cut, engraved, etched or carved to reveal the colours beneath. The technique is also known as cased glass or overlay glass, and it forms the basis of cameo glass, in which the outer layers are carved into relief designs.
Roman glassmakers produced layered cameo glass, the most famous surviving example being the Portland Vase. The technique was revived in nineteenth-century Bohemia, where glassworks produced vases, goblets and decanters with coloured overlays cut through in windows and facets to show clear or white glass. In England, Thomas Webb and Sons and other Stourbridge firms became celebrated for carved cameo glass in white over coloured grounds, while in France, Émile Gallé and Daum used multiple layers and acid etching to create Art Nouveau landscapes and floral designs. Layered glass was also widely used for lampshades, scent bottles and decorative tableware. Collectors look for crisp cutting, clean colour contrasts, quality of carving and signatures where relevant. Chips to cut edges, internal cracks and polished-out damage reduce value, and later reproductions of signed French cameo glass are common.
