Bronze casting is an ancient process whereby a sculpture - created from perishable material like clay or plaster - is transformed into a metal sculpture. It has been used, amongst others, by the Chinese, the Etruscans, Greeks, Romans,and in Benin.
There are several reasons to cast:
- several copies can be gained from one original (this is the reason why stone sculpture is cast sometimes);
-the reflective surface of the metal improves on the matt appearance of clay;
-the colours of the patination, the chemical reactions between patina, bronze and the surrounding air and rain, appeals to the eye;
-the sculpture lasts outdoors - like stone, metal survives outdoors nearly indefinitely;
- the sculpture is upgraded through a valuable material, and a good source of investing money.
Till recently, I have only cast my sculpture in bronze-resin, also called “Cold Bronze”: this is a much cheaper process (between one third or one half of the price), whereby the bronze is used in powder form, bonded with resin, rather than through heat.
The resulting sculpture consists still mainly (five parts out of six) of bronze;
Bronze Resin sculptures so far do not increase in value as reliably as “real” bronze sculptures do, as the look, weight, feel, and even “ring” of a real bronze sculpture appeals as a more aesthetic and a more durable object
So far, I have cast eight sculptures in partnership with Jason from the foundry Faberpyropus , who specialises in contemporary rather than traditional sculptures.
I can cast in bronze on commission, with the sculpture being ready usually within six weeks of ordering,
The casting process is a labour intensive process, and transformative akin to alchemy, the medieval science and quest for gold out of metal. Below is a description of
The Bronze Casting Process:
Hot wax is gently brushed onto the inside rubber layer of the separated halves of the mould. Several layers are applied. (1a/b)
Hot wax is gently brushed onto the separated halves of the mould, several layers are applied. (1a/b)
The mould is then bolted back together and filled with hot wax, which is swilled around the mould, and poured out when the desired thickness is achieved
When the wax has cooled and hardened the wax sculpture is removed from the mould.
The wax sculpture (”the wax”) is then worked, all the seams are welded. Any air bubbles or faults in the wax are repaired and it is re-textured to match the artist’s original sculpture.
Now there is a complete wax copy of the sculpture, soon to be traded in a for a bronze version
When the wax is ready for "investment", the decision is taken whether to split it into smaller sections - this can make the casting of an individual piece more economically viable
Core pins are placed into the wax to hold the investment core in place when the wax is melted away (= the short thin needles).
Runners and risers are also added to enable the molten metal to flow to all areas of the sculpture and to allow gases to escape the long tubes, with shorter onesbranching off to the sculpture).
The sections of wax are placed inside containers (“the flasks”) and
The investment powder is mixed in a very large bucket with water.(“Investment” is a mixture of plaster and silica).
The investment is poured over the wax sections, and fills the whole flask.
At this stage the flask may be placed in a vacuum chamber, as this helps the investment to completely cover and fill the wax, and prevent air bubbles forming on the surface of the sculpture. The flasks are then placed into the kiln and heated to 700 degrees: the wax is molten away and a void is left, to be filled with the molten bronze.
Once cooled, the bronze sculpture sections are carved out of its investment shell.
The three sculpture parts are cleaned, and the bronze runners and core pins are sawn away, and ground back
The three parts are welded together
the seams are still visible as a band of lighter or rainbow colour, but not as a raised surface
The process of finishing the bronze is known as “Chasing”. The chaser uses a variety of hand and machine tools to hide the seams of the sculpture, to amend any blemishes from the casting process and to re-texture the sculpture where needed.
Different attachments are used
The final stage of the process is the patination. The bronze is gently heated using a gas torch and a variety of chemicals are sprayed or brushed onto the surface. Different chemicals will produce different colours. Often several layers of chemicals are used to achieve the final patina.
Finally waxes are applied to protect the sculpture from erosion and the weather, and give it a sheen.
The sculpture is ready for the client