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       'Swan protecting her cygnets'                'By the Dawns Early Light'            'Leaping Panther'            

27" high x  34" wide                          11.5 inches high                     45" Long  x 37" High  


Casting a bronze   - 'Swan with Cygnets'  -  'Bald Eagle'  -   and 'Leaping Panther' bronze sculptures, using the traditional 'lost wax' process




Bald Eagle ; a partially solid bronze sculpture


Investment casting is a modern method of making bronze castings using the ancient art of the lost wax process to a high degree of accuracy and with a smooth surface finish. Outlined here are just some of the various stages required to produce three typical bronze sculptures by Ian G Brennan. From the original woodcarving 'master copies' to the completed bronze sculptures.

The first example shows during its various stages how the partially solid bronze sculpture of the Bald Eagle was produced. This is followed by stage photographs showing a much larger bronze sculptures of a 'Swan protecting her Cygnets', and also a 50 inches long 'Leaping Panther' both of which were hollow cast bronzes.


Original woodcarving 'master copy'




Master copy                          Wax version

Using the previously prepared mould ( see creating a mould page) melted wax is either painted or swilled against the inner surface of the flexible rubber mould to the desired thickness required for the finished metal casting. The two separate parts of the mould are placed together with clamps and a little hot wax poured into the cavity of the mould and again swilled around inside to cover the join between the two separate pieces of the mould.

When the wax has cooled the hollow wax replica of the original sculpture is carefully removed from the rubber mould and the 'runner system' or 'tree', which will eventually  channel the molten bronze into the sculpture is applied to the wax version of the sculpture. If there are a number of undercuts in the sculpture it can sometimes be helpful to remove the wax sculpture from the rubber mould whilst the wax is warm and therefore more pliable, but either way care must be taken to reduce breaking any of the delicate features of the sculpture.


wax tree                                                         various different patterns drying out

When these wax eagles are assembled upon the wax runner, the complete assembly is then carefully cleaned before being dipped or invested into a wet ceramic based slurry and coated with a fine dry refractory similar to these various patterns shown above. Once dry these coating operations are repeated several times and by progressively using coarser grades of refractory until the mould eventually reaches a sufficient thickness to withstand the force of the molten metal during the casting operation. As an added safety precaution on occasions it is sometimes necessary to wire the whole ceramic shell together to help prevent the molten heavy bronze bursting out through the shell when it is being poured.


pouring the molten bronze into the hot ceramic shells           when cooled the bronzes are removed from the shell 

Once all these various coats of ceramic have been applied and the 'tree' has been dried the ceramic shell is then placed in a steam oven and the wax is melted out - hence the name the 'lost wax process'. The shell is then fired at 1000.degrees centigrade to burn off any residual wax and to strengthen the ceramic mould. Once the bronze is melted in a high-frequency induction furnace it is poured into the hot shell, enabling the bronze to flow into all the detailed sections. After solidifying and cooling the ceramic shell is broken away from the bronze cast and the castings are cut away from the tree.


The polished bronze prior to colouring

The remaining pieces of the ceramic shell has then to be cleaned away from the sculpture by first tapping the bronze tree section of the sculpture with a hammer, the remaining smaller pieces of ceramic can then be removed by sand blasting. Hours of careful fettling is then required to clean up and finish the eagle sculpture, the bronze is then polished before the various chemical finishes are ready to be applied to the bronze.  


Traditional bronze patina - ( A )


A traditional bronze patina colour to the bronzes is usually achieved by painting on a chemical solution to the whole bronze casting whilst the bronze is cold. The weaker the solution the lighter the colour, when the correct colour is finally achieved to the sculpture, the bronze is heated up with a gas torch and melted wax is painted on to the bronze to seal in the colour and the sculpture is then allowed to cool slightly before it is finally polished with a soft brush.


Coloured Bald Eagle  - ( B )

In the case of the Bald Eagle to try and achieve a similar 'bald eagle' look without painting the sculpture, i.e. a lighter colour head, tail, feet and beak, this can be  achieved by carefully applying a with a brush a stronger chemical solution to the body of the Bald Eagle to achieve the almost black colour required of the eagles body feathers. By then applying a much weaker solution to the head, tail, feet and beak, the bronze is again then heated up and melted wax applied to seal in the colour of the bronze.



Painted Bald Eagle - ( C )


To achieve a similar but possibly more naturalistic appearance to the Bald Eagle was achieved by painting the bronze using acrylic paints and then wax polished. As before the almost black colour of the bald eagles body feathers was achieved by painting on a stronger solution of the appropriate chemical, applying some heat to the bronze with a gas torch and then sealing the bronze with wax. Once the sculpture has cooled, the bald eagles head, tail, feet and beak was then prepared for painting. The painted area on the bronze has first to be sealed with a metal primer before the white and yellow acrylic paint is applied, the whole sculpture is then given a final wax polish. 



'Swan and Cygnets' ; hollow bronze sculpture.



The bronze 'Swan protecting her Cygnets'


The moulding process required for the sculpture was very similar to the Bald Eagle, however as Ian's original wood sculpture of a Mute Swan defending her young was carved from a single piece of wood many years before it was decided to produce a limited edition of the Swan sculpture in bronze. As the rather angry Swan was carved with wings raised and feathers ruffled the sculpture therefore had many undercuts requiring a much more flexible three piece mould, which would enable both the original woodcarving and the moulded wax version to be removed from the mould without damage.


the three piece plaster and rubber swan mould


The Art foundry having successfully produced the mould of the Swan, returned the original woodcarving back to Ian along with the exact replica of the Swan which had now been cast hollow in green wax. The wall thickness of the wax would then determine the overall finished thickness of the bronze casting


Even though the wax swan was reproduced in fine detail it still takes Ian several days to re-work the wax Swan and Cygnets, taking the opportunity of using his original Swan woodcarving as a reference and continually re-defining all the fine detail into the wax replica. A rather tedious job he was quick to point out, but well worth the effort when the completed wax was eventually replicated in bronze. Once the fine detailing on the wax Swan has been completed, Ian then signs the base of the particular sculpture.



As this Swan sculpture is to large to be cast in one piece the wax has to be cut into much smaller sections before being returned to the foundry for casting separately. The process at the foundry is then very similar to the bald eagle sculpture described above, as the various wax sections of the sculpture are again  assembled upon the wax runner. These wax sections upon the tree are again carefully cleaned by dipping in alcohol and when dry continually dipped or invested, into a wet ceramic based slurry and coated with a fine dry refractory ceramic.




Once the separate bronzes have been cast and then carefully separated from the tree, all the pieces have to be carefully fettled, any holes or imperfections that might be found in the casting are carefully repaired using a bronze weld. The 'chaser's is one of the most important craftsman in the foundry, one of his tasks is to carefully weld the whole sculpture back together. This welding has to be so perfect that you cannot see any of the joins in the sculpture, a  highly skilled and time consuming process especially when the chaser is working on one of Ian's bird sculptures with all the many hundreds of individual feathers. 

Each of these detailed feather have many barbs carefully carved along the entire width of each feather, all of which have to carefully chased back into the bronze along the welded seam. The completed sculpture is then shot blasted all over with very fine pellets, which prepares the bronze sculpture for colouring, before sealing this patina in with wax.


The patina required to complete the Swans on these two occasions were both completely different, the Swan on the right was requested by the client to have a green mottled type of appearance, whereas the client requested to have the Swan on the left to have more normal bronze patina. 

The whole process to produce a sculpture like Ian's ' Swan protecting her Cygnets' from the mould to finally adding the patina to the completed bronze casting takes several weeks of full time work at the foundry, and if you add to this approximately three months of full time work for Ian to carve the original Swan  'master copy,' it is not surprising why 'genuine' bronze sculptures often prove to be rather expensive



'Leaping Panther' ;  bronze sculpture.


Original walnut woodcarving


The 'Leaping Panther' bronze sculpture was again moulded from one of Ian's original early wood sculptures, again the original woodcarving was carefully moulded and an exact copy produced in wax. This original 47 inches long 'Leaping Panther' was carved from a single piece of English walnut.


 The plaster and rubber mould along with the wax version of the panther

Once the two piece panther mould was made the wax version was produced, this hollow wax was panther was again cut into smaller pieces and attached to a  wax tree and cast in separate bronze pieces. These four various separate bronze castings once cleaned and removed from the tree were then ready for the chaser to start his work. Although on this panther sculpture there are no tiny feather to worry about the separate pieces again have to be welded together to disguise these weld joins, especially on a completely smooth sculpture like the panther presents itself with another, but no less difficult problems to the chaser.



As the sculpture is hollow in parts of the sculpture, such as parts of the panthers legs, small holes are cut into the wax which will enable a mixture of the ceramic material to be placed into the cavity. This ceramic mixture or grog is held in position by copper pins which are driven through both the outer walls of the wax sculpture and into the ceramic core. Once the casting has been completed this internal core is removed by sand blasting along with the other ceramic material covering the outer part of the bronze sculpture The little wax 'hatch' which was earlier removed is also cast in bronze at the same time and later welded back into position to cover these small holes.


Again on this occasion there was two different finishes required on a pair of these 'Leaping Panther' sculptures. The panther on the left had a patina added which gave a dark green onyx/marble type of effect, the other sculpture had a more traditional dark bronze patina.



Further examples of  Ian's smaller wax sculptures assembled upon the wax 'tree', prior to the wax runners and risers being attached.


Sea Otter                                    Golden Eagle                                  Swimming Otters




Sea Otter  feeding                                                Swimming Otters


After the molten bronze has been poured and allowed to cool, the hard ceramic shell is now being removed from the bronze tree and sculpture.



The two swimming bronze otters after being cleaned up and polished before being welded together and then coloured..




The completed sea otter feeding, along with the pair of swimming otters after being finished with an onyx effect colouring and then polished.




Home    Artist Information    Phoenix Rising   Selected Commissions    Wildlife Sculptures     HMS Victory     HMS Victory Sculpture  

  Creating an Wood/Bronze Sculpture    Creating a Relief Carving    Short TV Films   Creating a Bronze     Creating a Bald Eagle    Creating a Crest / Arms