The origins of the Lost Wax Castings are shrouded in antiquity, but it has been used for thousands of years to produce objects in metal which could not be produced any other way, due to the complexity of their form. It permits anything that can be modelled in wax to be faithfully transmuted into metal, and is still used today for certain industrial parts, dental restorations, fine jewelry, and sculpture.
While wax patterns were originally modelled by hand, and this can still be done, it is now possible to cast wax into molds as well, so that multiple copies may be made even though the wax pattern is lost in the process. Modern synthetic rubbers have been developed which capture very fine detail and can flex to release undercut areas of a model, greatly reducing the number of mold parts and the number of parting lines necessary, when compared to the earlier technique of using wet plaster molds. Waxes can be cast either solid or hollow, as the wax will coat the inside of a mold after it is filled and poured out. This process is repeated to build up the desired thickness of wax. The process is slightly different for jewelry and sculpture; the smaller quantities involved when making jewelry-sized pieces necessitate some adaptations to overcome the effects of surface tension, such as wax injection instead of simple pouring, and the use of a vacuum table or centrifugal casting machine to force metal into molds.
Lost Wax Castings sometimes called by the French name of cire perdue (from the Latin cera perduta) is the process by which a brass or bronze sculpture is cast from an artist's sculpture. Other metals such as silver and gold are also cast. Intricate works can be achieved by this method, primarily depending on the carver's skills. In industrial uses, the modern process is called investment casting. An ancient practice, the process today varies from foundry to foundry, but the steps which are usually used in casting small bronze sculptures in a modern bronze foundry are generally quite standardized.
After it is made and touched-up, the wax model is attached to a "pour-cup", which is funnel-shaped to channel the metal into the mold from the outside, using "gates"or "sprues" made from rods of wax , and a venting system is made the same way to convey air and other gasses out of the mold when it is filled with hot metal. Once the model is set up with its gates and vents, it is surrounded with a material that will cover it smoothly when wet and withstand high temperatures when baked. In some places an ancient technique involving cow-dung and clay is still used; a very fine mixture is painted on to capture the detail, then coarser layers are added to build up a mold that can be handled, baked, and poured into.