The Lost Wax Process

Clay Original of NocturneThe lost wax process is a traditional method of casting in bronze which has been used by sculptors for at least 5,000 years. Barbara Chen has selected lost wax bronze for the execution of her limited edition sculptures for its fidelity to her original sculpture and for the rich and solid appearance of bronze. Chen casts her sculptures at a world-class foundry in Joseph, Oregon. Chen creates her original sculptures in an oil-based clay placed on a steel and foam "armature" or structural skeleton which she builds herself. Working by eye, she spends several weeks to several months on each new sculpture. She always works to music ("everything from opera to calypso") because she finds the music inspires the poses and energy in her sculptures. Chen prefers to have two or three sculptures in progress at any given time, so that she can always have "fresh eyes" for the piece she is currently working on.

Rubber Mold of Nocturne After an original sculpture is completed by Chen, a rubber mold is carefully taken from the clay original in a process which takes several days. The oil-clay original remains soft, and is destroyed after the mold is taken. Several layers of hot wax are then poured into the rubber mold, resulting in a hollow replica of the original sculpture. The wax version of the sculpture is removed from the mold, and any imperfections such as air bubbles or seam lines are then "chased" away by hand. At this point in the process, Barbara Chen inspects and retouches each wax to assure fidelity to her original sculpture. A new wax is poured for each casting in an edition, and the mold is destroyed after the entire edition has been cast.

A Sprued Wax of Minuet The next step in the process is the addition to the wax sculpture of a network of wax "sprues" and "vents", which will act as channels through which the molten bronze will flow into the sculpture and gases will escape. For most sculptures, the wax reproduction must be cut into several pieces before sprueing in order to ensure a successful bronze pour. The placement and design of these channels is crucial; proper placement ensures a successful and complete filling of the mold before the bronze cools to a solid state, as well as perfect reproduction of minute details. A wax cup is connected to the sprues, which will serve as the receptacle into which the bronze is poured.

Over a period of approximately nine days, this wax "tree", consisting of the pieces of the wax sculpture, connected by a network of wax channels to a wax cup, is dipped alternately into ceramic slurry and silica sand. During this period, each coat of slurry and sand is allowed to dry and gain strength. This "ceramic shell" is then placed in a kiln, melting out the wax (hence the term "lost wax") contained in the tree, and firing the shell. The ceramic shell mold is now hardened and ready to receive molten bronze.

Chen inspects bronze casting Bronze is melted in a crucible to 2100 degrees Fahrenheit, and poured into the pre-heated ceramic shell through its cup. The sculpture, sprues and cup are filled with molten bronze. After the bronze cools completely, the shell is chipped and sandblasted off the bronze casting. The sprues and vents are removed from the bronze, which is now a set of pieces identical in form to the cut- up wax original prior to sprueing. These bronze pieces of the sculpture then are welded together by highly skilled craftsmen, and the resulting bronze sculpture is again "chased", removing any imperfections from the casting process.

Chen inspects bronze casting Barbara Chen again inspects each sculpture at this stage to assure that every detail is perfect before the patina is applied to the sculpture. A variety of chemical solutions is carefully applied by hand by expert patineurs while the sculpture is heated with a torch.

Patineur applying finish Chen works closely with the patineurs in the development and execution of each patina she chooses for her sculptures.

The resulting lost-wax bronze sculpture is then sealed and mounted to a custom-made stone or wood base. The finished work of art is an enduring sculpture which will bring joy and beauty into the lives of those who view it for generations to come.

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©2000 Barbara Chen. All rights reserved. Last update on 2/4/2000.