Niello is a form of decorative inlay that has been used since at least the Roman times. The name comes from the Latin nigellum meaning somewhat black. For antique jewellery, the process involved engraving a design onto a piece of metal, usually silver, then filling the hollowed out areas with a powdered black alloy and heating it so that the black powder melts and fuses into the engraved patterns. According to Pliny, the powdered alloy comprised 3 parts silver, 2 parts sulphur and 1 part copper. Over the centuries the recipe changed and lead was added to the alloy around the 11th century. Sometimes the silver was gilded.
While niello was usually used to fill engraved patterns, it was also used as a background and was painted on to a slightly roughened surface and then heated to fuse it.
By the 18th century, niello jewellery was mainly produced by Russian craftsmen and its popularity had waned. It had been displaced by enamel which could be produced in a range of colours. It became popular again when examples of Niello jewellery was exhibited at the Great Exhibition of 1851. Most of the jewellery came from Russia, although some French and English jewellers also began to produce items. Niello jewellery remained popular up until the Art Deco period. It primarily was used for chains, fobs, bracelets, lockets, cuff links, and watches, as well as pens and boxes. The base of the jewellery was normally silver, 800 as it withstood the firing process better than sterling silver, and it was often decorated with pink gold.
One other place apart from Russia still produces neillo items and that is Thailand. Thai nielloware became known after WWII as soldiers and tourists bought jewellery back as presents. The distinctive silver and black jewellery usually contains images of characters from an important allegorical story in the Hindu religion called the Ramayana, known in Thailand as Ramakien.