§ 105 Enamels Over Reliefs
See now another sort of work in silver and in gold, commonly called enamel, a kind of painting intermingled with sculpture, suitable for lining the bottom of pieces intended to hold water.286 This when worked on gold, needs the very finest gold; and when on silver, the silver at least of the quality of the giulio.287 The following method is necessary in order that the enamel may remain in its place and not run beyond its proper limits. The edges of the silver288 must be left so fine that when looked at from above they escape the eye. In this way is made a flat relief contrary to the other kind,289 in order that when the enamels are put over it, it may take its darks and lights from the height and depth of the intaglio. Then glass enamels of various colours are picked out and carefully fixed with the hammer;290 they are kept in little bowls filled with clear water, separated and distinct one from the other. Those which are used with gold are different from those that serve for silver291 and they are worked in the following manner. The enamels are lifted out separately with the most delicate little silver shovel and spread in their places with scrupulous cleanliness, and this is done over and over again, according as the enamel adheres properly, and so with all the quantity that is needed at the time. This done, an earthenware receptacle, made on purpose, is prepared; it must be perforated all over and have a mouthpiece in front, then the muffle, which is a little perforated earthenware cover that will prevent the charcoal falling from above, is introduced into this receptacle, and above the muffle the space is filled up to the top with oak charcoal kindled in the ordinary way. In the empty space which is left under the aforenamed cover the enamelled object is placed on a very thin iron tray to feel the heat gradually and is kept there long enough to admit of the enamels melting, when they flow all over almost like water. Which done, it is allowed to cool, and then with a ‘frassinella,’ that is, a stone for sharpening iron tools, and with sand such as is used for drinking glasses moistened with clear water, it is rubbed till it becomes perfectly level. When the process of removing all superfluity is finished, the object is placed in the actual fire, to be melted a second time in order that the whole surface may become lustrous.292 Another sort is made by hand, and polished with Tripoli plaster (powder) and a piece of leather, but of this there is no need to make mention.293 I have however described the above because being, like the other processes, of the nature of painting it seemed to come into our subject.