Description of the compositions and properties of niellos, including those of Pliny, Eraclius, Theophilus, and Cellini. All except Pliny, whose recipe did not contain Pb, used a ternary mixture of sulphides of Ag, Cu, and Pb. Cellini's mixture is much closer to the eutectic and thus has a sharper melting point. X-ray diffraction, physical, and chemical tests are described.