In order to produce large size bronze sculptures we have set up an innovative method, called “Chemical Sand Casting”. This process allows the reproduction of large size sculptures and bas-relief (up to 250 cm) as a single piece therefore requiring fewer welds. We start the process from the plaster model, eliminating the need for a mould nor a wax copy and take an impression directly from the model, supplied by the artist, in sand mixed with a special hardening agent.
Within a few hours the sand hardens (at room temperature) against the model and thus we obtain an exact impression of the sculpture made up of various blocks of sand. When the hardened sand negative is completed, we remove the model and apply an even layer of putty (just a few millimeters thick), which will determine the thickness of the bronze. Finally the “core” is made to fill the inner part of the mould thereby ensuring the bronze cast is hollow.
When the core is hard the mould is again opened, the layer of putty used to determine the thickness of the bronze wall is removed between the outer mould and the inner core and the mould closed again, taking great care that all the blocks fit together perfectly. At this point, the bronze can be poured through openings previously formed in the sand mould together with the “casting runners” that allow the molten metal to flow to every part of the sculpture. Once the metal has cooled, the burnt sand mould is removed to free the bronze. The “casting runners” are cut and the process of chasing and finishing begins. Finally the application of various acids to the heated bronze surface will create the patina or color of the finished piece.