Although many jewellers work purely in metal, it is useful to have a werking knowledge of other types of materiais, and it is always interesting exploring :he finishes and effects that can be achieved with them, as they often provide a colourful dividing line to subtle metallic tones. Some jewellers preferto work in a particular material and will end up knowing a great deal about its properties and the techniques that are most appropriate to use. Many materiais have specific working properties, for example, refractory metals can be anodized but not annealed or soldered, and thermoplastics can be heated and formed while soft. Natural materiais such as wood, bone, shell and leather have been used •’or body adornment since antiquity, alongside base and precious metals and gemstones. These materiais are often combined with more lately developed synthetical products, which are commonly used in contemporaryjewelry making – plastics, rubbers, concrete and magnets have a range of applications including mould making and model making within jewelry practice .
PRECIOUS METALS: GOLD
Applications
The high cost of gold compared to silver means that it is often used for contrasting colour or accents on silver pieces in order to keep the overall material costs down. The cost of the material influences many of the techniques that are used – it is more usual to engrave gold than to etch it because the dissolved metal in the acid solution is not as easily reclaimed. Gold can be used in thinner gauges than silver as it is not as soft, and sheet can be up to 0.2 mm (two gauges) thinner without any loss of intact strength; this also helps to reduce the cost of the metal used in a piece.
White-gold alloys are much harder and stron-ger than yellow, and for this grounds prong and claw settings for valuable stones, as well as mech-anisms, are often made from white gold.
Twenty-two-carat gold is a very rich yellow colour, but too soft for most applications. However, its malleability makes 22-carat gold ideal for bezel-setting very soft stones. Eighteen-carat gold probably has the best working properties, being a little harder than silver and hard enough to retain a high polish, making it suitable for most applications; this alloy contains a high percentage of gold, so it is perceived to have a high intrinsic value. Fourteen-carat gold also has good working properties, but is a paler shade of yellow than higher-carat golds; it has the lowest melting point of all the gold alloys.
Nine-carat gold is the palest, hardest and least expensive alloy of gold, but having such a low percentage of gold in the alloy means that it also has a low intrinsic value.
