By examining the sculptures in this way, their fabrication methods could be assessed and compared with documented 16th century casting practices. All of the bronze busts appear to have been cast using the lost-wax technique, a technique well known and well recorded in the Renaissance . For example, Benvenuto Cellini, Guglielmo della Porta's contemporary and competitor, meticulously described his own casting methods. Traditionally, plaster was used. The mold is heated and the wax is melted out so that the shape of the model is retained between the walls of the mold and the inner core.
Molten metal is poured into the mold and assumes the shape left by the wax model.
Finally, the mold is broken open, and finishing touches are made to the metal sculpture. What became apparent in the first step of the technical examination of the busts was not that the casting method chosen for these bronzes was atypical of Renaissance sculptures, but that the approach to the fabrication of the sculptures was quite similar within the group. Remnants from the casting process such as small holes left by the core pins or excess metal left along the truncation of the bust from the sprues or runners appeared consistent on the sculptures. This, in turn, suggested that the busts were made by the same individual or workshop that had achieved a working method that was capable of yielding consistent results. Bacchus and a Faun, a 16 th century bronze sculpture by an anonymous Italian.