Archaeologists have analyzed 2,900-year-old stone carvings and a long-ignored chisel from the Iberian Peninsula, revealing that local craftspeople produced steel long before previously thought.

Lost-wax casting – also called investment casting , precision casting , or cire perdue ( French: [siʁ pɛʁdy] ; borrowed from French ) [ 1 ] – is the process by which a duplicate sculpture (often a metal , such as silver , gold , brass , or bronze ) is cast from an original sculpture. Intricate works can be achieved by this method. Illustration of stepwise bronze casting by the lost-wax method The oldest known examples of this technique are approximately 6,500 years old (4550–4450 BC) and attributed to gold artefacts found at Bulgaria's Varna Necropolis . [ 2 ] A copper amulet from Mehrgarh , Indus Valley civilization , in present-day Pakistan, is dated to circa 4,000 BC. [ 3 ] Cast copper objects, found in the Nahal Mishmar hoard in southern Israel , which belong to the Chalcolithic period (4500–3500 BC), are estimated, from carbon-14 dating , to date to circa 3500 BC. [ 4 ] [ 5 ] Other examples from somewhat later periods are from Mesopotamia in the third millennium BC. [ 6 ] Lost-wax casting was widespread in Europe until the 18th century, when a piece-moulding process came to predominate. The steps used in casting small bronze sculptures are fairly standardized, though the process today varies from foundry to foundry (in modern industrial use, the process is called investment casting). Variations of the process include: "lost mould ", which recognizes that materials other than wax can be used (such as tallow , resin , tar , and textile ); [ 7 ] and "waste wax process" (or "waste mould casting"), because the mould is destroyed to remove the cast item. [ 8 ] [ 9 ] On the left is an example of a rubber mould, often used in the lost-wax process, and on the right is the finished bronze sculpture. A video illustrating the process used by the National Park Service to create bronze sculptures at the Saint-Gaudens National Historical Park in the United States Casts can be made of the wax model itself, the direct method, or of a wax copy of a model that need not be of wax, the indirect method. These are the steps for the indirect process (the direct method starts at step 7): Model-making. An artist or mould-maker creates an original model from wax, clay , or another material. Wax and oil-based clay are often preferred because these materials retain their softness. Mouldmaking. A mould is made of the original model or sculpture. The rigid outer moulds contain the softer inner mould, which is the exact negative of the original model. Inner moulds are usually made of latex , polyurethane rubber or silicone , which is supported by the outer mould. The outer mould can be made from plaster , but can also be made of fiberglass or other materials. Most moulds are made of at least two pieces, and a shim with keys is placed between the parts during construction so that the mould can be put back together accurately. If there are long, thin pieces extending out of the model, they are often cut off of the original and moulded separately. Sometimes many moulds are ne