This pictorial presents the development of a data sculpture, followed by our reflections inspired by Research through Design (RtD) and Dahlstedt's process-based model of artistic creativity. We use the notion of negotiation between concept and material representation to reflect on the ideation, design process, production, and the exhibition of "Slave Voyages" - a set of data sculptures that depicts slave traffic from Africa to the American continent. The work was initially produced as an assignment on physicalization for the Design course at the Federal University of Rio de Janeiro. Our aim is to open discussion on material representation and negotiation in the creative process of data physicalization.