'By the Dawns Early Light'

Bald Eagle Bronze - 11.5 inches high


Casting the bronze Bald Eagle Sculpture using the 'lost wax' method


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 also with a smooth surface finish. Outlined here are just some of the various stages required to produce a typical bronze casting from the original master copy to in this example, the completed Bald Eagle bronze sculpture.
The master copy of the Bald eagle was originally carved from lime wood, the surface of the wood sculpture was then bleached, stained and sealed with a wood sealant to help prevent the rubber mould sticking to the Bald eagle woodcarving..





   master copy                                               wax version

Using the original eagle as the master copy, a flexible 'negative' rubber mould with a hard plaster 'jacket' was produced. The making of this negative can begin once the most suitable joint-lines on the original sculpture has been decided upon, which will enable the sculpture to be removed from the mould, without either damaging the original woodcarving or the rubber part of the mould itself.
A thin coat of wax is applied to the original wood sculpture which will help prevent the rubber sticking to the woodcarving, then a layer of soft clay is placed over the whole sculpture, which in turn is followed by a layer of moulding plaster to make a 'mother-mould'. Each half of this mother mould is then removed and the clay extracted, the liquid rubber is then pored into the space left by the clay and allowed to cure. Once the master copy is totally enveloped with the moulding rubber, the plaster 'jacket' can be removed and the flexible rubber stripped from the original Eagle sculpture.
The flexible rubber is then placed back into the plaster jacket and melted wax can then be either painted or swilled against the inner surface of the rubber to the desired thickness required for the finished metal casting. When the wax has cooled the hollow wax replica of the original sculpture can be removed from the rubber mould and the 'runner system' or 'tree' to channel the molten bronze is applied to the wax.

  wax tree                                                         various different patterns drying out

When these wax eagles are assembled upon the wax runner, the complete assembly is then 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.

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


Hours of careful fettling is then required to clean up and finish the eagle sculpture, the bronzes are then polished before the various finishes are ready to be applied.   


 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 bees 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 a more naturalistic appearance to the Bald Eagle this can be achieved by painting the bronze using acrylic paints and then wax polished. As before the almost black colour of the eagles body feathers is achieved by painting on a stronger solution of the chemical and sealing the bronze with wax. Once the sculpture has again cooled down from being heated with the gas torch, the bald eagles head, tail, feet and beak can then be prepared for painting. The painted area on the bronze has to first be sealed with a metal primer before the white and yellow acrylic paint is applied, the whole sculpture is then given a final polish with wax.. 
 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

  ( Return )