The basic method of lost-wax casting has been widely practiced on the African continent for centuries. While it is difficult to establish how the method was developed or introduced to the region, it is clear that West African sculptors were casting brass with this method for several hundred years prior to the arrival of the first Portuguese explorers along the coast in 1484. The technique requires a great deal of skill, involving extensive knowledge of both pottery and metalworking, and a careful attention to changing temperatures to prevent unwanted cracking or other damage to either the clay mold or to the metal sculpture during the casting process. Some of the earliest and most accomplished bronzeworks found in Africa date to the tenth century and are from a site called Igbo-Ukwu.
The process begins with beeswax, latex, or another material with a low melting point. It must be soft enough for carving fine details, but hard enough to retain its shape. After the wax object has been carved, increasingly coarse layers of clay are applied to the object and allowed to dry. The first and finest clay slips capture the wax details in the smooth mold, and the coarser clay layers provide strength. The entire assemblage is fired, causing the original wax carving to melt away, leaving only a baked clay shell. Liquid metal is poured into the empty mold and left to cool and harden. Later, the clay exterior is broken open, revealing the finished metal object beneath. In direct lost-wax casting, the object produced is always unique, as the mold is necessarily destroyed as part of the casting process.
West African sculptors have elaborated on this basic technique in a variety of ways. Many works were produced through multiple castings and by uniting different sections of a large vessel or figure. In addition, many of the brasses are actually a thin sculpture of hollow metal. In this case, the wax sculpture is formed over a clay core. The two clay parts are attached with spikes. Made from iron, the melting point of the spikes is hotter than either the wax or brass, holding the materials in place through the phases of heating and cooling. If reachable, the clay core is broken up and removed from the interior of the completed brass work.