The combination of archival and collection-based research with laboratory analyses allows to meet some of the initial objectives of the project. Copper and brass were not the primary purpose of the trade and local production seems to have been a side activity. They had nevertheless a widespread use in the Great Congo Trade, displaying a diversity of shape and value. Copper from the Niari Basin was primarily traded through the local network before reaching regional trade routes where they were traded alongside brass imported from the coast.
The exploratory pXRF analyses allowed to outline that even though brass was dominant among the objects analysed, it did not fully replace locally produced copper at the end of the 19th century as the assumption has been for a long time. Thanks to a characteristic chemical composition, copper objects likely to originate from the Niari Basin have been indeed identified in distant areas along the Upper Congo River as late as the first decades of the 20th century. In addition, by comparing the composition of brass rods imported from Europe – the main raw material for making brass objects - with the locally cast objects, the level of recycling along the trade networks can be assessed because the brass is losing Zn at every melt. The limited identified number of objects made of recycled metal all comes from peripheral areas. These objects would reflect the higher number of intermediaries between the source of metal and the final object as suggested by historical sources while riverine groups along the Congo River, the main trade axe, had a more direct access to new copper or brass ingots.
The organisational structure of the Great Congo trade may explain the widespread use of copper and brass. While some nodes attracted a larger flow of goods because of their strategic position, the complex interaction of local and regional networks made every portion of the route important. Negotiation at the different interfaces was crucial for the proper running of trade. Even though natural features seem to have influenced the general layout of the routes, local actors played an as important role in the actual itineraries of the trade, being able to reshape them at the local level. In such a set of complex and heterogenous networks, the material properties of brass and copper allowed them to be easily transformed in response to the local demands. They could then cross the many thresholds of the Great Congo Trade by being endowed with new attributes, facilitating the exchange at the interface between different socio-economic or political spheres.
The results illustrate the importance of investigating trade at a more local scale to understand the dynamic of exchange over long distances in the Congo Basin and set the ground for further research on trade for earlier periods.
