metalwork
- Related Topics:
- enamelwork
- bronze work
- copper work
- ironwork
- silverwork
metalwork, useful and decorative objects fashioned of various metals, including copper, iron, silver, bronze, lead, gold, and brass. The earliest human-made objects were of stone, wood, bone, and earth. It was only later that humans learned to extract metals from the earth and to hammer them into objects. Metalwork includes vessels, utensils, ceremonial and ritualistic objects, decorative objects, architectural ornamentation, personal ornament, sculpture, and weapons.
General processes and techniques
Many of the technical processes in use today are essentially the same as those employed in ancient times. The early metalworker was familiar, for example, with hammering, embossing, chasing, inlaying, gilding, wiredrawing, and the application of niello, enamel, and gems.
Hammering and casting
All decorative metalwork was originally executed with the hammer. The several parts of each article were hammered out separately and then were put together by means of rivets, or they were pinned on a solid core (for soldering had not yet been invented). In addition, plates of hammered copper could be shaped into statues, the separate pieces being joined together with copper rivets. A life-size Egyptian statue of the pharaoh Pepi I in the Egyptian museum, Cairo, is an outstanding example of such work.
After about 2500 bce, the two standard methods of fabricating metal—hammering and casting—were developed side by side. The lost-wax, or cire perdue (casting with a wax mold), process was being employed in Egypt by about 2500 bce, the Egyptians probably having learned the technique from Sumerian craftsmen (see sculpture). Long after the method of casting statues in molds with cores had superseded the primitive and tedious riveting process, the hammer continued as the main instrument for producing art works in precious metals. Everything attributable to Assyrian, Etruscan, and Greek goldsmiths was wrought by the hammer and the punch.
Embossing, or repoussé
Embossing (or repoussé) is the art of raising ornament in relief from the reverse side. The design is first drawn on the surface of the metal and the motifs outlined with a tracer, which transfers the essential parts of the drawing to the back of the plate. The plate is then embedded face down in an asphalt block and the portions to be raised are hammered down into the yielding asphalt. Next the plate is removed and re-embedded with the face uppermost. The hammering is continued, this time forcing the background of the design into the asphalt. By a series of these processes of hammering and re-embedding, followed finally by chasing, the metal attains its finished appearance. There are three essential types of tools—for tracing, for bossing, and for chasing—as well as a specialized tool, a snarling iron or spring bar, which is used to reach otherwise inaccessible areas. Ornament in relief is also produced by mechanical means. A thin, pliable sheet of metal may be pressed into molds, between dies, or over stamps. All of these methods have been known from antiquity.
Chasing
Chasing is accomplished with hammer and punches on the face of the metal. These punches are so shaped that they are capable of producing any effect—either in intaglio (incising beneath the surface of the metal) or in relief—that the metalworker may require. The design is traced on the surface, and the relief may be obtained by beating down the adjacent areas to form the background. Such chased relief work sometimes simulates embossed work, but in the latter process the design is bossed up from the back. The detailed finish of embossed work is accomplished by chasing; the term is applied also to the touching up and finishing of cast work with hand-held punches.
Engraving
To engrave is to cut or incise a line. Engraving is always done with a cutting tool, generally by pressure from the hand. It detaches material in cutting. When pressure is applied with a hammer, the process is called carving.
Inlaying
The system of ornamentation known as damascening was much practiced by the early goldsmiths of Damascus; hence the name. It is the art of encrusting gold wire (sometimes silver or copper) on the surface of iron, steel, or bronze. The surface upon which the pattern is to be traced is finely undercut with a sharp instrument. The gold thread is forced into the minute furrows of the cut surface by hammering and is securely held.
Niello is the process of inlaying engraved ornamental designs with niello, a silver sulfide or mixture of sulfides. The first authors to write on the preparation of niello and its application to silver were Eraclius and Theophilus, in or about the 12th century, and Benvenuto Cellini, during the 16th. According to each of these authors, niello is made by fusing together silver, copper, and lead and then mixing the molten alloy with sulfur. The black product (a mixture of the sulfides of silver, copper, and lead) is powdered; and after the engraved metal, usually silver, has been moistened with a flux (a substance used to promote fusion), some of the powder is spread on it and the metal strongly heated; the niello melts and runs into the engraved channels. The excess niello is removed by scraping until the filled channels are visible, and finally the surface is polished.
Enameling
There are two methods of applying enamel to metal: champlevé, in which hollows made in the metal are filled with enamel; and cloisonné, in which strips of metal are applied to the metal surface, forming cells, which are then filled with enamel. (For a detailed discussion, see enamelwork.)
Stephen Vincent GrancsayGilding
Gilding is the art of decorating wood, metal, plaster, glass, or other objects with a covering or design of gold in leaf or powder form. The term also embraces the similar application of silver, palladium, aluminum, and copper alloys.
The earliest of historical peoples had masterly gilders, as evidenced by overlays of thin gold leaf on royal mummy cases and furniture of ancient Egypt. From early times, the Chinese ornamented wood, pottery, and textiles with beautiful designs in gold. The Greeks not only gilded wood, masonry, and marble sculpture but also fire-gilded metal by applying a gold amalgam to it and driving off the mercury with heat, leaving a coating of gold on the metal surface. From the Greeks, the Romans acquired the art that made their temples and palaces resplendent with brilliant gilding. Extant examples of ancient gilding reveal that the gold was applied to a ground prepared with chalk or marble dust and an animal size or glue.
Beating mint gold into leaves as thin as 1⁄280,000 inch (0.00001 centimeter) is done largely by hand, though machines are utilized to some extent. After being cut to a standard 37/8inches (9.84 centimeters) square, the leaves are packed between the tissue-paper leaves of small books, ready for the gilder’s use.
The many substances to which the gilder can apply his art and the novel and beautiful effects he can produce may require special modifications and applications of his methods and materials. Certain basic procedures, however, are pertinent to all types of gilding. For example, the ground to be gilded must be carefully prepared by priming. Flat paints, lacquers, or sealing glues are used, according to the nature of the ground material. Metals subject to corrosion may be primed (and protected) by red lead or iron oxide paints. With pencil or chalk the gilder lays out his design on the ground after the ground has been prepared and is thoroughly dry. Patterns may also be laid down by forcing, or pouncing, powdered chalk or dry pigment through paper containing perforations made with pricking wheels mounted on swivels; the swivel arrangement permits the attainment of the most intricate of designs.
To create an adhesive surface to which the gold will be securely held, the area to be gilded is sized. The type of size used depends on the kind of surface to be gilded and on whether it is desirable for the size to dry quickly or slowly. When the size has dried enough so that it just adheres to the fingertips, it is ready to receive and retain the gold leaf or powder.
Gold leaf may be rolled onto the sized surface from the tissue book. Generally, however, the gilder holds the book firmly in his left hand with the tissue folded back to expose as much leaf as is needed and detaches that amount with a pointed tool, such as a sharpened skewer. He then picks up the leaf segment with his gilder’s tip, a brush of camel’s hair set in a thin cardboard holder, and carefully transfers it to its place in his design. The leaf is held to the tip by static electricity, which the gilder generates by brushing the tip gently over his hair. For some gilding operations the gilder uses a cushion to hold his pieces of leaf. This is a rectangular piece of wood, about 9 by 6 inches (23 by 15 centimeters) in size, which is padded with flannel and covered with dressed calfskin; a parchment shield around one end protects the delicate leaf from disturbance by drafts of air. When the gilding is completed, the leaf-covered area should be pounced with a wad of soft cotton of surgical grade. Rubbing with cotton burnishes the gold to a high luster. Application of a gilder’s burnisher—that is, a highly polished agate stone set in a handle—also imparts a fine, high finish to the metal. Loose bits of gold, or skewings, may be removed from the finished work with a camel’s hair brush.
Leaf gold may be powdered by being rubbed through a fine-mesh sieve. Powdered gold is so costly, however, that bronze powders have been substituted almost universally for the precious metal. When gold leaf is employed in the gilding of domes and the roofs of buildings, it is used in ribbon form. For finishing processes, such as burnishing and polishing, see sculpture.
Ellen Louise Young