Post 501 by Gautam Shah
Surface finishing or decorating with a foreign material is a very ancient technology. Metals have been embellished by several techniques. Metals have been coated by metal plating, surface alloying and deposition. Metals have been inlayed with metals, precious stones and objects.
These processes include:
● Damascening a technique of encrusting gold, silver or copper wires in the finely chased surfaces of iron, steel, or bronze.
● Niello is made from black metallic alloy of sulfur with silver, copper, or lead. It is filled in chased or engraved patterns over silver. The surface is heated for the niello to melt. On polishing the surface gets a dual metallic effect.
● Granulation is made by soldering or fusing granulated beads of silver or gold to effect a bloom to the surface than of a beaded surface.
● Filigree is made by forming a fine network of very thin wires fused selectively and than fixed on a metal surface of an object.
● Ajouré is similar to filigree but the fine network is created by cutting or piercing the patterns in the metal. Raised patterns or cut out motifs are also fused onto the surface.
● Embellishments with Other Materials were formed using precious stones, exotic substances such as rare woods, metals, ivory, horn, beads, sea shells, jade, and amber, and niello-work, fixed into chased or performed cavities or depressions. Fixing was by wire, metal forming, heat-fusing, thread knitting and knotting.
● Inlay works are of many varieties. Pre-formed cavities or depressions are filled in by many different materials such as wood, stones and metals. The fixing is with tight fitting, adhesives, or by hammering a ductile metal.
● Gilding is application of metal like silver, gold, silver, palladium, aluminum, and copper alloys, in the form of very thin foils. Gilding by gold or silver foils requires as no adhesives as sufficient electrical charges attract the foil to the base, however for permanent fixing (on exterior use) some form of adhesives are used.
● Overlays can be defined as metal sheathing or cladding by metal sheets that are slightly heavier than used for gilding. Overlaying is also done by applying a gold amalgam (gold+mercury) and than removing the mercury with heat.
Enamelling is a metal embellishment technique wherein a vitreous glaze is heat-fused to create a very long lasting decorative effect of brilliant colours. (Read on > Enamels).
Painted Enamels are used to coat and decorate the surfaces of metal objects. Enamelling offers a long-lasting , and brilliantly coloured finish. Technically Enamel is a comparatively soft glass or ceramic, a melted compound of flint or sand, lead, and soda ash or potash. This glass, called flux, frit or fondant, is clear with a tinge of blue. This ground and remelted with oxide colours, but shade variations are achieved by changes in the mix proportion for the flux. Painted Enamels are used in translucent and opaque forms. Similarly the hardness of the flux depends on the mix proportions. Hard Enamels require hire temperature for fusing, and have better resistant to weather. Enamels have a size limitations so are used as important inserts in art compositions, with size enhancement through drawn or carved framing etc.
Painted Enamels are used for Jewellery, arms, armour, horse trappings, mirror frames, dishes, bowls. Enamels are also used for interior decoration such as ceilings and walls (as in the rooms of the châteaus of France).
Painted Enamels are like miniature oil paintings. These are made on a metal base or plate covered with a layer of an opaque enamel. The opaque or white enamel base is further embellished with ‘glass forming but with colouring materials’, rendered by fine needle painting, spraying, screen printing, spattering, scratching or block printing. Separate firing is required for each of the colours. Artists created portraits and other art subjects on very small metal plates, surpassing richness of larger canvass-based oil paintings. Painted Enamels being very small could be carried anywhere as a personal item of collection or treasure. The colours are permanent and non-yellowing or fading. The painted enamel has remained a craft and is not accepted as medium of art. The painted enamels of China are known as Canton (Guangzhou) enamels. Painted enamels are termed by the Chinese yangci (foreign porcelain).
Coloured enamel embellishments were created over arms, armour, mirrors, bowls, cups, chalices, spoons, and miniature pendants, tableware, wall and ceiling panels, signages, table clocks, and snuffboxes.
Five main types of enamelling processes are used:
● Champlevé (French= raised field) enamels are created by scratching or etching a copper surface, which are than filled-in with pulverized enamel material, fired and polished.
● Cloisonné (French= partitioned) has very small partitions or cloisons formed with thin metal strips. The partitions are filled with pulverized enamel and fired.
● Basse-Taille (French= low cutting) process is a kind of champlevé, but is applied to silver or gold. Here the depressions are filled with translucent enamel, which allows the substrate or patterns on it to be seen.
● Plique-à-jour (French=open braids) enamelling resembles cloisonne, but here the partitions form a separable lattice. The lattice is removed after firing, giving an effect of stained glass. It is exceptionally fragile work.
● Encrusted Enamel: Encrusted enamel or enamel en ronde bosse is prepared by spreading of an opaque enamel paste over slightly roughened surfaces of objects such as small figures.