The spruing does not have to be hollow, as it will be melted out later in the process. The carefully planned spruing usually begins at the top with a wax "cup," which is attached by wax cylinders to various points on the wax copy. The wax copy is sprued with a treelike structure of wax that will eventually provide paths for the molten casting material to flow and for air to escape. Wax pieces that were moulded separately can now be heated and attached foundries often use registration marks to indicate exactly where they go. The wax now looks like the finished piece. The wax is dressed to hide any imperfections. Each hollow wax copy is then "chased": a heated metal tool is used to rub out the marks that show the parting line or flashing where the pieces of the mould came together. The model-maker may reuse the mould to make multiple copies, limited only by the durability of the mould. ![]() This hollow wax copy of the original model is removed from the mould. With this method it is more difficult to control the overall thickness of the wax layer. After this the rest of the wax is poured out again, the mould is turned upside down and the wax layer is left to cool and harden. ![]() Another method is to fill the entire mould with molten wax and let it cool until a desired thickness has set on the surface of the mould. ![]() This is repeated until the desired thickness is reached. Once the mould is finished, molten wax is poured into it and swished around until an even coating, usually about 3 mm ( 1⁄ 8 inch) thick, covers the inner surface of the mould. Sometimes many moulds are needed to recreate the original model, especially for large models. If there are long, thin pieces extending out of the model, they are often cut off of the original and moulded separately. 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. The outer mould can be made from plaster, but can also be made of fiberglass or other materials. Inner moulds are usually made of latex, polyurethane rubber or silicone, which is supported by the outer mould. The rigid outer moulds contain the softer inner mould, which is the exact negative of the original model. A mould is made of the original model or sculpture. Wax and oil-based clay are often preferred because these materials retain their softness. An artist or mould-maker creates an original model from wax, clay, or another material. These are the steps for the indirect process (the direct method starts at step 7): 4.5 Greece, Rome, and the MediterraneanĬasts 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.(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) and "waste wax process" (or "waste mould casting"), because the mould is destroyed to remove the cast item. The steps used in casting small bronze sculptures are fairly standardized, though the process today varies from foundry to foundry. Lost-wax casting was widespread in Europe until the 18th century, when a piece-moulding process came to predominate. ![]() 3700 BC, making them more than 5,700 years old. Conservative estimates of age from carbon-14 dating date the items to c. and the objects discovered in the Cave of the Treasure ( Nahal Mishmar) hoard in southern Palestine (region), which belong to the Chalcolithic period (4500–3500 BC). Other examples from somewhat later periods are from Mesopotamia in the third millennium B.C. The oldest known example of this technique is a 6,000-year old amulet from the Indus Valley Civilization. Intricate works can be achieved by this method. Lost-wax casting (also called " investment casting", "precision casting", or cire perdue which has been adopted into English from the French, pronounced ) is the process by which a duplicate metal sculpture (often silver, gold, brass or bronze) is cast from an original sculpture. 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.
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