THE PROCESS FOR CASTING GOLD objects like ornaments and jewelry is the same as that for casting Asante brass weights. Goldsmiths who were skilled in the art of working with the precious metal were also responsible for casting the necessary boxes, scales, weights, and scoops used in storing and weighing gold dust.
In the early 1970s, David Crownover, Executive Secretary of the Museum, and William Kohler, Research Associate in MASCA, made several trips to Africa for the Penn Museum prior to publishing an article about goldsmithing and lost wax casting in the Spring 1973 issue of Expedition. They described the process of a goldsmith in Kumasi to better understand the craft.
Wild beeswax was harvested or traded in. Working the wax into a mold (foa) required rolling and shaping on a wood block (adwini pono) to get a basic shape. Heated blades (sekan), spatulas made from wood or bone, and bamboo or iron needles were used to carve intricate details.
Thin, hollow wax rods were attached to the completed mold in places that would not ruin the final product. When the mold was covered in clay, they would be left in place to melt away and allow a channel for the molten metal.
The wax mold was allowed to harden. Clay slip, a fine mixture of clay, water, and charcoal, was either painted on or the mold was dipped into it. Multiple layers of slip would be applied to ensure each detail was captured and that the mold would be protected when the clay casing was applied.
The entire piece was allowed to dry completely. The next step was to heat the mold in a furnace (ebura), so that the molten wax could be poured out. Where the wax rods had been was now an opening, and a clay cup (semoa) to hold pieces of brass was attached with clay around this opening. The new joint must now dry as well.
When the time came to cast the piece, the mold was placed in the furnace with the cup below. A charcoal fire, controlled by using a bellows (afa), was used to heat the metal until molten. Once ready, the smith used a pair of tongs (odabaw) to flip the mold upside-down, allowing the molten metal in the cup to flow into the cavity. The mold and metal within would be left to cool in this position.
Once completely cooled and hardened, the clay cast was cracked open. The casting was thoroughly cleaned; bits of blackened clay would have been baked on and had to be chipped away. A mixture of water and lime juiced was used to scrub it further, and then the smith would set to work on trimming any excess metal or imperfections in the casting.
An experienced caster would judge the sizeof the mold and how much metal was required to produce a specific weight. Should the weight come out too far below or too heavy for the intended measure, alterations were made to allow the weight to be used for the next higher or lower standard. If it was close enough, alterations could be as simple as adding an extra ring of brass or drilling a hole into the piece. Some of the examples in the Penn Museum collection appear to reflect this practice.