Association of Art and Antique Dealers
International Confederation of Traders in Works of Art
Materials - Metal
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. Some types of brasses are called bronzes. Brass is a substitutional alloy. Brass has a muted yellow color, somewhat similar to gold. It is relatively resistant to tarnishing, and is often used as decoration and for coins.
Bronze
Bronze is any of a broad range of copper alloys, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminium or 
silicon. It was particularly significant in antiquity, giving its name to the Bronze Age.
"Bronze," in turn, is perhaps ultimately taken from the Persian word "berenj," meaning "brass.” With the exception of steel, bronze is superior to iron in nearly every application. It is considerably less brittle than iron. Bronze only oxidizes superficially; once the surface oxidizes, the thin oxide layer protects the underlying metal from further corrosion.
Copper
Copper is a ductile metal with excellent electrical conductivity and is rather supple in its pure state and has a pinkish lustre which is (beside gold) unusual for metals which are normally silvery white. It finds use as a heat conductor, an electrical conductor, as a building material, and as a constituent of various metal alloys.
Mercury
A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure. Mercury occurs in deposits throughout the world and it is harmless in an insoluble form, such as mercuric sulfide, but it is poisonous in soluble forms such as mercuric chloride or methylmercury. Mercury ores usually occur in very young orogenic belts where rock of high density are forced to the crust of the Earth, often in hot springs or other volcanic regions. Although murcury is very rare, it was used in barometers, thermometers and other scientific apparatus until it’s toxicity started to cause concern. Mercury is often used in barometers.
Ormolu
Ormolu (from French or moulu, signifying gold ground or pounded) is an 18th-century English term for applying finely ground, high-karat gold to an object in bronze. The French refer to this technique as bronze doré, which is used to this day though the item may be merely painted with a gold-tone paint. The manufacture of true ormolu employs a process known as mercury gilding or fire gilding, in which a solution of nitrate of mercury is applied to a piece of copper, brass, or bronze, followed by the application of an amalgam of gold and mercury. The item was then exposed to extreme heat until the mercury burned off and the gold remained, adhered to the metal object.
Most mercury gilders died by the age of 40 due to exposure to the harmful mercury fumes. The principal use of ormolu was for the decorative mountings of furniture, clocks, lighting devices, and porcelain.
Pewter
Pewter is a metal alloy, traditionally between 85 and 99 percent tin, with the remainder consisting of copper and antimony, acting as hardeners, with the addition of lead for the lower grades of pewter, which have a bluish tint. The word pewter is probably a variation of the word spelter. Unlidded mugs and lidded tankards may be the most familiar pewter artifacts from the late 17th and 
18th centuries, although the metal is also used for many other items including porringers, plates, dishes, basins, spoons, measures, flagons, communion cups, teapots, sugarbowls, beer steins and cream jugs.
In the early 19th century, changes of fashion witnessed a decline in the use of pewter flatware, but increased production of both cast and spun pewter tea sets, whale-oil lamps, candlesticks.
Spelter
Zinc in its nonscientific context it is sometimes called spelter; it is impure zinc containing about three percent lead and other impurities. Spelter can often be mistaken for bronze, although it is much lighter and more brittle. Spelter is commonly used for figurines as it can be portrayed as it’s better quality look alikes; Bronze / Ormolu / Iron.