Niello is more than simply a drawing on metal. That would come under the head of engraving. A graver is used to cut out the design on the surface of the silver, which is simply a polished plane. When the drawing has been thus incised, a black enamel, made of lead, lamp black, and other substances, is filled into the interstices, and rubbed in; when quite dry and hard, this is polished. The result is a black enamel which is then fused into the silver, so that the whole is one surface, and the decoration becomes part of the original plate. The process as described by Theophilus is as follows: "Compose the niello in this manner; take pure silver and divide it into equal parts, adding to it a third part of pure copper, and taking yellow sulphur, break it very small... and when you have liquefied the silver with the copper, stir it evenly with charcoal, and instantly pour into it lead and sulphur." This niello paste is then made into a stick, and heated until "it glows: then with another forceps, long and thin, hold the niello and rub it all over the places which you wish to make black, until the drawing be full, and carrying it away from the fire, make it smooth with a flat file, until the silver appear." When Theophilus has finished his directions, he adds: "And take great care that no further work is required." To polish the niello, he directs us to "pumice it with a damp stone, until it is made everywhere bright." There are various accounts of how Finiguerra, who was a worker in niello in Florence, discovered by its means the art of steel engraving. It is probably only a legendary narrative, but it is always told as one of the apocryphal stories when the origin of printing is discussed, and may not be out of place here. Maso Finiguerra, a Florentine, had just engraved the plate for his famous niello, a Pax which is now to be seen in the Bargello, and had filled it in with the fluid enamel, which was standing waiting until it should be dry. Then, according to some authorities, a piece of paper blew upon the damp surface, on which, after carefully removing it, Maso found his design was impressed; others state that it was through the servant's laying a damp cloth upon it, that the principle of printing from an incised plate was suggested. At any rate, Finiguerra took the hint, it is said, and made an impression on paper, rolling it, as one would do with an etching or engraving.