The Bronze process ...
Creating a bronze sculpture is an involved process. Robbie spends a good deal of time working on the composition of his work considering the best and most interesting pose for his subject matter. He also takes into consideration the impact of negative space and silhouette when deciding on the final moment that he is going to capture in bronze, in addition to taking into account technical issues such as the weight shift and the balance of the sculpture. For example, in creating his African Fish Eagle he brilliantly combined the pose of the swooping bird as it captures a fish with a technically superbly balanced bronze with the weight and fulcrum coinciding with the outstretched leg and talon of the bird. This aspect of the creative process has always been preceded by considerable research and observation of his subject in loco and by handling museum skin specimens to confirm correct proportions. Robbie will make a Marquette before embarking on the creation of his final piece.
Once he is satisfied with his design and in order to create the final sculpture Robbie prefers to work with different microcrystalline waxes which have a plasticity but yet are hard enough to keep the exact texture and detail he requires. From this sculpture, Robbie then has to make a mould and for this he uses a good quality silicone rubber which is able to retain a high quality and detailed impression of this original. This is then backed by a fibreglass surround or 'jacket' to secure the whole in place.
A wax is then melted to pour into the base of the mould in sufficient quantity to provide a hollow wax shell. The wax picks up the finest detail from the silicone mould. This hollow wax process allows Robbie to make a number of editions of a bronze. Each wax is individually fettled to remove the casting line from the join of the mould in order to create a smoothed complete whole. Wax pipes, runners and a feeder cup are attached to the wax sculpture to allow air and feed metal to escape.
In order to hold the bronze metal a ceramic mould has to be made and this is done by dipping the wax into a slurry of liquid ceramic then different grades of ceramic sands. This process is repeated about ten times before being left to dry. The ceramic mould is then turned upside down in a kiln and the wax is melted out leaving a hollow shell before being turned the right way up and fired to 900 C. The glowing hot mould is then ready to receive the molten bronze which has been heated at 1150 C. The bronze is poured in replacing the wax and hence the process is known as the 'lost wax process'. The bronze is left to cool before the ceramic shell is shattered using a hammer and chisel and tenacious remnants of the ceramic are sand blasted off to clean the bronze of any residue.
The bronze sculpture is assembled by welding the different castings together and the join lines are yet again fettled using sharp chisels, grinders and files. Finally a bronze patination is applied using different chemicals on the surface depending on the desired colour required. The bronze is then wax polished and buffed to its final form.