niello (nēĕlˈō) [key] [Ital. from Latin nigellus = blackish], black metallic alloy of sulfur, copper, silver, and usually lead, used as an inlay on engraved metal. The metal surface is brushed with a borax solution as a flux, dusted with powdered niello, then heated. After cooling, the surface is scraped and shows a black pattern in the incised lines. Pulling a paper proof of the design in order to make corrections before inlaying is said to have been the start of printing from an engraved plate. The Egyptians are credited with originating niello decoration, which was practiced in classical times, spread throughout Europe during the Middle Ages, and came into high repute in the 15th cent. with the work of the Florentine goldsmith Finiguerra.
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