Foil

A thin metal foil placed behind a gemstone within a closed-back setting to improve its appearance. Metallic foil improves the reflectivity of certain gemstones, whilst coloured foils act as colouring agents when placed behind colourless materials, such as paste and rock crystal.

The practice of foil-backing gemstones can be traced back to Minoan times (circa 2000 BC), however it is most closely associated with the Georgian and early Victorian periods.