section_path: Materials and techniques/Metal
section_name: Metal
paragraph_text: Metal
  
  Bronze and related copper alloys are the oldest and still the most popular metals for cast metal sculptures; a cast bronze sculpture is often called simply a "bronze". Common bronze alloys have the unusual and desirable property of expanding slightly just before they set, thus filling the finest details of a mould. Their strength and lack of brittleness (ductility) is an advantage when figures in action are to be created, especially when compared to various ceramic or stone materials (see marble sculpture for several examples). Gold is the softest and most precious metal, and very important in jewellery; with silver it is soft enough to be worked with hammers and other tools as well as cast; repoussé and chasing are among the techniques used in gold and silversmithing.
  
  Casting is a group of manufacturing processes by which a liquid material (bronze, copper, glass, aluminum, iron) is (usually) poured into a mould, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solid casting is then ejected or broken out to complete the process, although a final stage of "cold work" may follow on the finished cast. Casting may be used to form hot liquid metals or various materials that cold set after mixing of components (such as epoxies, concrete, plaster and clay). Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods. The oldest surviving casting is a copper Mesopotamian frog from 3200 BCE. Specific techniques include lost-wax casting, plaster mould casting, and sand casting.
  
  Welding is a process where different pieces of metal are fused together to create different shapes and designs. There are many different forms of welding, such as Oxy-fuel welding, Stick welding, MIG welding, and TIG welding. Oxy-fuel is probably the most common method of welding when it comes to creating steel sculptures because it is the easiest to use for shaping the steel as well as making clean and less noticeable joins of the steel. The key to Oxy-fuel welding is heating each piece of metal to be joined evenly until all are red and have a shine to them. Once that shine is on each piece, that shine will soon become a 'pool' where the metal is liquified and the welder must get the pools to join, fusing the metal. Once cooled off, the location where the pools joined are now one continuous piece of metal. Also used heavily in Oxy-fuel sculpture creation is forging. Forging is the process of heating metal to a certain point to soften it enough to be shaped into different forms. One very common example is heating the end of a steel rod and hitting the red heated tip with a hammer while on an anvil to form a point. In between hammer swings, the forger rotates the rod and gradually forms a sharpened point from the blunt end of a steel rod.