NIELLO is a method of ornamenting metal plates, practised chiefly during the middle ages Upon the plate—which was most commonly of silver, but sometimes of gold or copper—the design was first sketched with a style, and then somewhat deeply engraved with a burin or graver. [Esenasio.] The lines thus incised were filled with a composition called from its colour tzissellans (whence the Italian and, the plate being polished, an effect w•aa produced something like that of a pen-and-ink drawing. The composition was an amalgam of quicksilver, silver, and lead, (with occasionally a little copper) melted together, and blackened by the addition of sulphur. When cold the nigellum was pounded and kept ready for use. This powder was laid, with borax, on the incised lines, into which it was melted by a gentle heat being applied to the back of the plate, which when cold was polished and burnished, and the work was complete. This kind of engraving is of considerable antiquity. It appears to have been practised in the early centuries of Christianity by the goldsmiths who prepared the more costly articles for ecclesiastical purposes. Two small gold cups which bad in the centre crosses in 'Mello were bequeathed by the Abbot Leodebode to the convent of St. Aignan &Orleans in the 7th century. At the beginning of the 9th century a pectoral cross, of which ono side was decorated in Mello, was sent by Nichephorus, patriarch of Constantinople, to Pope Leo III.; and towards the end of the same century, various articles of silver engraved in niello were made at Constantinople for the church of St. Mark at Venice. The art. in these early times seems to have been chiefly practised by Byzantine artists; but in the 10th century we fad it practised both in Italy and Germany, though the workmen may possibly have been Greeks. From the I2th century niello seems to have formed a regular part of the goldsmith's art, and it was applied to the ornamentation of a great variety of articles, as well for secular as for ecclesiastical purposes. The Italian goldsmiths especially acquired great skill in the art, and produced works of exceeding beauty of deign and execution.
As mentioned under Exentiviso, niello is regarded as the parent of engraving in the modern sense of the term, that is, for taking impres sions on paper. Tho application is usually ascribed to 3faso Finne guerra, the most famous of the Florentine workers in niello. lu order to observe the progress of their work the niellatori were accustomed to take caste from it at various stages in clay, upon which they poured melted sulphur, and thus obtained faesimiles of their engraving.
Into these lines in the sulphurs, as they are called, they rubbed a composition of oil and lamp black, and were thus able to judge of the appeamnee of the plate after the insertion of the nigellum. According to Vraari, and other Italian authorities, it occurred to Finneguerra that he might save himself much of this troublesome process by filling the lines in the original plate with a similar composition, and taking impressions directly from it upon damped paper. Not only was his experiment successful, but these impressions on paper soon grow to be so much in request that niellatori found it a profitable occupation to prepare plates especially for their production ; and their extension to the imitation of paintings and drawings soon followed, and engraving became a distinct profession. At the same time, however, the working in Mello proper seems to have declined ; since Benvenuto Cellini relates that by 1515 the method of executing niello was nearly for gotten in Florence, when he, stimulated by the admiration expressed for the nielli of Finneguerra, applied himself with great diligence and entire success to the restoration of the lost art. Of this period many beautiful including suits of armour and other large articles, adorned with eiedH are still extant, as well as numerous smaller articles. The art, however, gradually passed out of use, and old Moth are now comparatively rare, and placed among the most precious artiolca of public and private collections. Among the public museums, the British 31 use= is one of the richest in nielli, and in impressions In sulphur and on paper—having about 70 silver plates, including some of extreme rarity and beauty of style. several fine sulphurs, and above a hundred proofs on paper, some of which are unique. Reference has been made to these last in tho article ENGRAVtao : it will be enough therefore to add that a case has recently bxen placed in the King's Library, open consequently to public inspection, which contains some of the finest of Mai, sulphurs, awl proofs, so arranged as to illustrate the history of the art, and its connection with that of engraving. l'ho national museums at Paris, Vienna, Berlin, and Dresden, are also rich in nielli ( Duchesne,Essoi ear ka ; Bartach, Le Pcintre Grareur, vol. xiii ; Paraavant, he Peislre Grareor, vol. t ; Ottley, /figory of Enyrarisg.)