Wednesday, June 13, 2007
In creating jewellery, gemstones, coins, or other precious items are often used, and they are typically set into precious metals. Alloys of nearly every metal known have been encountered in jewellery -- bronze, for example, was common in Roman times. Modern jewellery usually includes gold, white gold, platinum, palladium, or silver. Most American and European gold jewellery is made of an alloy of gold, the purity of which is stated in karats, indicated by a number followed by the letter K. American gold jewellery must be of at least 10K purity (41.7% pure gold), (though in England the number is 9K and is typically found up to 18K (75% pure gold). Higher purity levels are less common with alloys at 22 K (91.6% pure gold), and 24 K (99.9% pure gold) being considered too soft for jewellery use in America and Europe. These high purity alloys, however, are widely used across Asia, the Middle East, and Africa. Platinum alloys range from 900 (90% pure) to 950 (95.0% pure). The silver used in jewellery is usually sterling silver, or 92.5% fine silver.
Other commonly used materials include glass, such as fused-glass or enamel; wood, often carved or turned; shells and other natural animal substances such as bone and ivory; natural clay; polymer clay; and even plastics. However, any inclusion of lead or lead solder will cause an English Assay office (the building which gives English jewellery its 'stamp of approval, the Hallmark) to destroy the piece.
Beads are frequently used in jewellery. These may be made of glass, gemstones, metal, wood, shells, clay and polymer clay. Beaded jewellery commonly encompasses necklaces, bracelets, earrings, and belts. Beads may be large or small, the smallest type of beads used are known as seed beads, these are the beads used for the "woven" style of beaded jewellery.
Advanced glass and glass beadmaking techniques by Murano and Venetian glassmasters developed crystalline glass, enameled glass (smalto), glass with threads of gold (goldstone), multicoloured glass (millefiori), milk-glass (lattimo) and imitation gemstones made of glass. As early as the 13th century, Murano glass and Murano beads were popular.
Silversmiths, goldsmiths, and lapidaries methods include forging, casting, soldering or welding, cutting, carving, and "cold-joining" (using adhesives, staples, and rivets to assemble parts).
Diamonds, long considered the most prized of gemstones, were first mined in India. Pliny may have mentioned them, although there is some debate as to the exact nature of the stone he referred to as Adamas; Currently, Africa, Australia, and Canada rank among the primary sources.
The British crown jewels contain the Cullinan Diamond, part of the largest gem-quality rough diamond ever found (1905), at 3,106.75 carats. Now popular in engagement rings, this usage dates back to the marriage of Maximilian I to Mary of Burgundy in 1477.
Although diamonds are considered the most prized of all gemstones, many other precious stones are used for jewellery. Some gems, for example, amethyst, have become less valued as methods of extracting and importing them have progressed. Some man-made gems can serve in place of natural gems, an example is the cubic zirconia, used in place of the diamond.
For platinum, gold, and silver jewellery there are many different techniques to create different finishes. The most common however are: high-polish, satin/matte, brushed, and hammered. High-polished jewellery is by far the most common and gives the metal the highly-reflective and shiny look. Satin, or matte finish reduces the shine and reflection of the jewellery and is commonly used to accentuate gemstones such as diamonds. Brushed finishes give the jewellery a textured look, and are created by brushing a material (similar to sandpaper) against the metal, leaving 'brush strokes'. Hammered finishes are typically created by using a soft, rounded hammer and hammering the jewellery to give it a wavy texture.