Similar experiments in surface treatment and patination were applied to horn, a decidedly non-precious material that exemplified art nouveau jewelers’ emphasis on beauty and artistic effect over intrinsic value. Processed primarily from the horns of domestic cattle, the material had been used for centuries to make utilitarian objects such as spoons and combs, but rarely for jewelry. Although attractive when polished, horn was valued primarily for its versatility; its thermoplastic properties meant it could be flattened and molded under heat and pressure, and it could be bleached, dyed, or stained to imitate more expensive materials such as jet and tortoiseshell.
Lalique was the first person to show a piece of jewelry incorporating horn at the Salon of the Société des Artistes Français in 1896, and the following year he presented a whole showcase of decorative combs in horn and ivory that was greatly admired.10 Other jewelers, including Gaillard, Vever, and Aucoc, quickly followed, intrigued by horn’s mellow translucence, its strength and flexibility, and the great variety of surface effects that could be produced upon it. Lalique and Gaillard were particularly praised for the delicate tints and luminous iridescent skin or “bloom,” which they used to great effect in their many decorative haircombs.11 While the exact formulas and techniques used to produce these patinas are not known, the powdery whitish films found on many objects seem to have been produced by bathing or painting the surfaces with a mild acid solution.12
Art nouveau jewelers also used horn to achieve remarkably delicate and transparent representations of natural structures, such as sycamore seeds and insect wings, in works such as Aucoc’s dragonfly brooch(Figs. 1, 4). Each of the wings is carved from a thin sheet of horn, obtained by delaminating the growth layers of the horn during processing.13 Each of the wing pieces would have undergone several rounds of soaking and shaping under heat and pressure, and perhaps been treated with tallow to enhance its transparency.14 It was then cut to shape, heated, and pressed and allowed to cool between the two halves of a mold of wood or metal. Next the surface of each wing was painstakingly carved away to a thickness of between 1 and 1.5 millimeters, leaving the veins as tiny raised ridges. Holes were cut to permit the insertion of shaped collets set with diamonds and jewels of cabochon enamel (a technique by which the enamel surface is built up to form a domed shape, similar to a cabochon gemstone). Deeper pockets were cut into the surface to accommodate the large teardrop-shaped elements set into each wing, and the bands of platinum-set diamonds riveted to the top edge of each. As a finishing touch, the horn was drilled or cut away behind each individual stone and cell of enamel to permit light to pass through more easily.
A butterfly brooch also attributed to Aucoc is similar in design, materials, and execution to the dragonfly, but the overall effect is quite different, largely because of the way the horn wings have been treated (Fig. 13). They are thicker than the dragonfly’s (approximately 2 to 3 millimeters) and fairly flat on the back. The high relief on the front is the result of carving rather than molding, with the veins carved into the surface rather than resting above it. To give the surface a pearlescent sheen and slightly striated appearance, recalling the rows of tiny scales on an actual butterfly’s wings, it was most likely washed with acid to break down the material between the horn’s natural layers and make their edges more prominent. The surface may also have been stained or treated with other chemical compounds to give it a metallic quality.15 This surface, while not as delicate and subtle as the patinas favored by Gaillard and Lalique, also acts as an effective background for the open-backed cabochon enamel elements, which seem to glow like stained-glass windows.16
Glass was another material favored by art nouveau jewelers for its aesthetic qualities rather than its intrinsic value, and Lalique was again the first of his contemporaries to feature this material in his jewelry. His experiments with glass began in the 1890s, as an extension of his work with enamel, and he found cast glass to be a particularly effective material for the representation of complex three-dimensional forms. He also learned to enhance its luminous quality by enameling it with opalescent colors and by frosting the surface with acid. For the carnation brooch in Figure 6, Lalique cast the flower in clear glass, and selectively acid-frosted the petals and polished their edges to make the flower seem white and opalescent and to enhance its lively three-dimensional quality.