The use of the lost wax technique for creating bronze reproductions of sculptings was known to the Egyptians and Greeks several thousands of years ago and has not really changed substantially since then. New materials are being used, and some new technology has been adopted to speed up the process---but the process remains the same.
Some of the major steps required for this process include:
1. Building an armature which will furnish a sturdy skeleton for the model and prevent the media (clay, wax, plaster, plastilene, etc.) from slipping.
2. Modelling the media to a finished piece
3. Dividing the model with a continuous line of thin copper or other type of shim material so that the mold will part evenly and easily. For complicated and/or large sculptings, it may be necessary to cast the model in separate parts (i.e., cutting the model into sections), later putting the pieces together at the wax and/or bronze stage.
4. Making the master mold. This mold will be the original mold from which all successive editions of the sculpture will be made. The mold is prepared by building several layers of latex or silicone-rubber around the model followed by a secondary, supporting shell of plaster or fiber glass.
5. Removing the media from the parted mold.
6. Coating the open sections of the mold with layers of hot wax after which the mold is reunited and molten wax is poured in and out until the proper thickenss is achieved. This thickness will ultimately determine the thickness and weight of the bronze reproduction. When the wax impression is removed from the mold, after rejoining the pieces, it will be a hollow wax replica of the original model.
7. "Chasing". or cleaning, detailing, and remodelling the wax replica as necessary.
8. Making the second mold using the wax replica. The wax model is filled with ceramic and coated with several (up to 10) layers of different grades of ceramic/plaster,sand mixtures (slurry). Tunnels or "gates" are designed to allow the entry of molten bronze and exit of liquified wax. The ceramic mold is heated and the wax liquified and allowed to exit through the preformed gates, thus meriting the descripor "lost wax".
9. Breaking away the ceramic to recover the solidified bronze statue (or its parts).
10. Chasing, texturing, welding and sometimes remodelling the bronze to render a satisfactory replica of the original model.
11. Patinating the bronze by applying chemicals under high heat to hasten the ageing of the metal. When the "right" patina is achieved, the statue is coated with a protective layer of hard wax.
This process usually takes between three and four months for small sculptings and can take a year or more for larger pieces which require much assembly, welding and chasing. In many cases, the artist will do most of the chasing or remodelling of the wax and bronze replicas. If a foundry (such as Bronzart in Sarasota, Florida: Rick Frignoca and his team at Bronzart produced all of the bronzes shown on this site) has expert craftspeople and sculptors on its team, the artist may choose to let the staff perform this work. For the first reproduction, it is usually a good idea for the artist to be involved as there will be no reference model to work from. In any case, the expertise of the foundry and the sculptor must be combined to produce a quality product. This is a time consuming and expensive process and accounts for the high price of fine bronze sculptings.
It is important to note that, althought the first mold may be used several times, depending on the number of editions stipulated by the artist, no two works will be exactly the same. Each bronze is the product of new wax and ceramic molds and many hours of individualized chasing and re-modelling. When investing in bronze sculpture, it is important to look for the engraved signature of the artist and the edition number and limitation. If a foundry stamp was not applied, the artist or dealer should be able to furnish a certificate of athenticity from the foundry.
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