niello

noun, plural ni·el·li [nee-el-ee] /niˈɛl i/.

1. a black metallic substance, consisting of silver, copper, lead, and sulfur, with which an incised design or ground is filled to produce an ornamental effect on metal.
2. ornamental work so produced.
3. a specimen of such work.
4. a print on paper made from an incised metal plate before the application of niello and associated especially with 15th-century Italy.

verb (used with object), ni·el·loed, ni·el·lo·ing.

5. to decorate by means of niello; treat with niello or by the niello process.

noun plural -li (-lɪ) or -los

1. a black compound of sulphur and silver, lead, or copper used to incise a design on a metal surface
2. the process of decorating surfaces with niello
3. a surface or object decorated with niello

verb -los, -loing or -loed

4. (tr) to decorate or treat with niello