Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal. Silver occurs naturally in its pure, free form as an alloy with gold and other metals, as well as in minerals such as argentite and chlorargyrite. Most silver however, is produced as a by product of copper, gold, lead, and zinc refining.
Silver has long been valued as a precious metal, and is used as an investment, to make ornaments, jewelry,high-value tableware, utensils, and currency coins. Today, silver is also used in electrical contacts and conductors, in mirrors and in catalysis of chemical reactions. Its compounds are used in photographic film, and dilute silver nitrate solutions are used as disinfectants and microbiocides. While many medical antimicrobial uses of silver have been supplanted by antibiotics, research into clinical potential continues.
Jewelry and silverware are traditionally made from sterling silver, also know as standard silver, and is an alloy of 92.5% silver with 7.5% copper. In the US, only an alloy consisting of at least 90% fine silver can be marketed as “silver”. Sterling silver, which is stamped 925, is harder than pure silver, and has a lower melting point than either pure silver or pure copper. With the addition of germanium, the patented modified alloy called Argentium Sterling silver is formed.
Historically, the training and guild organization of goldsmiths included silversmiths, and the two crafts remain largely overlapping.
Unlike blacksmiths, silversmiths do not shape the metal while it is red-hot, but instead, work it at room temperaturewith gentle and carefully placed hammer blows. The essence of silversmithing is to take a flat piece of metal and totransform it into a useful object using different hammers, stakes and other simple tools. Because silver is such amalleable metal, silversmiths have a large range of choices with how they prefer to work the metal includingcasting the metal into intricate decorative designs.
Bronze is an alloy consisting primarily of copper, usually with tin as the main additive. It is hard and tough, andit was so significant in antiquity that the Bronze Age was named after the metal. There are many different bronzealloys but modern bronze is typically 88% copper and 12% tin. Historical “bronzes” are highly variable incomposition, as most metalworkers used whatever scrap was on hand. Commercial and architectural bronzes aremore properly regarded as brass alloys because they contain zinc as the main alloying ingredient. Bismuth bronze isa bronze alloy with a composition of 52% copper, 30% nickel, 12% zinc, 5% lead, and 1% bismuth; it is able to hold agood polish and so is sometimes used in light reflectors and mirrors. Other bronze alloys include aluminium bronze,phosphor bronze, manganese bronze, bell metal, arsenical bronze, speculum metal and cymbal alloys.
Typically, bronze only oxidizes superficially; once a copper oxide layer is formed, the underlying metal is protectedfrom further corrosion. Bronzes are softer and weaker than steel and are less stiff for the same bulk. It also resistscorrosion and metal fatigue more than steel and is a better conductor of heat and electricity than most steels. Themelting point of bronze varies depending on the ratio of the alloy components but is usually about 1,742 °F.
For centuries bronze has been and is still used for a variety of purposes. Ship propellers and submerged bearingsare commonly made in bronze and it is widely used for cast sculpture. Many common bronze alloys have the unusual,desirable property of expanding slightly just before they set, thus filling in the finest details of a mold. Bronzeparts are tough and typically used for bearings, clips, electrical connectors and springs. Unlike steel, when bronze isstruck against a hard surface, it will not generate sparks, so is used to make hammers, mallets, wrenches and otherdurable tools to be used in explosive atmospheres or in the presence of flammable vapors. With so many diverseapplications, bronze will continue to be an important alloy for years to come.