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Reading Selection, Lesson 7

Lost Wax Casting:
Exploiting Melting Points for Art and Industry

Knowledge of melting points is very important for people who work with metal. Let's look at the goldsmiths who live in a small village in Côte d'Ivoire (Ivory Coast), West Africa, as an example. They make jewelry and other items by using a technique that has been in existence for thousands of years. It is called “lost wax casting.”
wax model with sprues

The artist carves a model in wax (usually beeswax). Wax is soft, and the artist can use it to produce intricate carvings. After completing the model, he attaches tiny wax rods (called sprues) to it that will produce channels in the mold for draining the wax and receiving the gold.


In this technique, an artist produces a clay mold around an easily carved substance: wax. When the mold is heated, the wax, which has a melting point less than 70 °C, melts away. The hard clay mold can then be used to produce jewelry made from metals with high melting points. The artists often use gold, which has a melting point of more than 1000 °C.  

 

Wax model covered with clay. The artist covers the wax figure with several layers of fine wet clay. Coarse clay is then added in layers to complete the mold. The clay mold is placed in an oven and heated until it hardens. The wax melts and runs out of the mold (in other words, it’s lost!).
Wax model in artist's hand being cleaned. The wax model is carefully cleaned before the first layer of fine clay is added.

 

 

 

 

 

 

 

Casters working at furnace.
Air is pumped by hand bellows into a charcoal furnace. This produces the high temperature needed to melt gold.

The pictures here show the major steps in lost wax casting. In these pictures the artist is using gold.

Crucible containing gold pieces.
Pieces of gold are placed in a crucible.

 

 

 

 

 

 

Crucible being attached to the mold.
The crucible is attached to the mold. The two parts are then sealed together using more clay.

 

Molding of gold piece.
The mold and gold are heated together in a furnace. When the gold has melted, the mold is turned over so that the metal flows into it. The mold cools. The clay mold is cracked off, leaving a casting.

 

 

 

 

 

 

 

 

 

 

 

 

illustration of an artist filing rough edges from the cast gold.
The artist files away a few rough edges, and the jewelry is ready.
Figurine created using the lost wax casting method. The lost wax method has been used to produce a variety of objects, including this figure of a king from Nigeria.

 

 

 

 

 

 

 

 

 

 

 

 

Precision parts created using lost wax casting. Recently, new uses have been found for lost wax casting. It is one technique used to produce precision parts, such as these—designed for aircraft and other machines.

 

 

 

 

 

 

 

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