The illustration depicts the process of making metal sculptures using the lost-wax casting process. The steps involved in the process are as follows:

1. Wax model: A wax model of the sculpture is built up around a clay core. Wax is used because it is soft enough for carving fine details, but hard enough to retain its shape at room temperature.
2. Clay mold: Clay is applied to the wax model in layers of increasing coarseness, and left to dry. The inner, finer layers capture every detail of the sculpture in a smooth mold. The outer, coarser layers (clay mixed with sand) provide strength.
3. Melting wax:The clay-covered wax model is then baked in a kiln. Because wax has a low melting point, the wax model melts away inside the clay, leaving a hardened shell mold. This clay mold is then used to make the final sculpture.
4. Molten metal: Molten (liquid) metal is poured into the clay mold and left to cool and harden. For this sculpture of an African head, a mixture of copper, zinc, and lead was used.
5. Metal sculpture: When the metal has cooled, the clay shell is broken open to reveal the finished metal sculpture.