Process

History of Bronze - The word denotes a place in time where mankind crossed a line into modern civilization. Around 2500 BC humanity used fire in the ultimate of promethium quests - to create. The creation of bronze, an alloy of copper and tin often with a small amount of lead, changed the landscape of humanity.

The metal was first used for making tools and weapons. It soon became valued for its aesthetic beauty and a myriad of different objects from bowls to sculpture were being either cast or hammered from sheets of bronze. Because it could be remelted it was also viewed by many early traders as a commodity thus the precious bronze images revered by their kings were often among the booty of warring armies, carried off and melted down for some other use. This is why so few early bronze sculptures exist today. Even the bronze "David" cast in Michelangelo's time was melted down for cannons.

The transformation of bonze into the beautiful sculptures that we see in museums or galleries is the craft of the the founder. This skill and knowledge has long been revered. Today it still holds fascination for the general public. The moment of pulling the crucible then pouring its gleaming hot liquid is surrounded by a mystical aura. Most sculptors do not mold or cast their own work but are involved at certain key points along the way. Thanks to the new technology of the past 30 years there is a renaissance of bronze casting in our day. Still the long process remains essentially the same in it's steps - each one demanding care for detail from the beginning to end. It is a matter of months to take an original sculpture through the full process of a final bronze casting.

All these factors - the history, the process, the great benefits of the medium are why so many sculptors turn to bronze and why it is so cherished by collectors.

The Lost Wax Investment Casting Process - This process is also known as "cire perdue" from the french meaning sincere and without wax. This stems from the early foundry being unable to weld to repair faults in castings so the used wax to fill holes and disguise defects as well as the wax model that was lost making the mold.The lost wax or cire-perdue process is the traditional method of bronze casting. It has been around for at least 5000 years and was used by the early Egyptians, Greeks, Africans and masters of the Italian Renaissance.
In some places an ancient technique involving cow-dung and clay is still used. In a modern variation on the cow-dung and clay method, a silicaceous slurry is used to cover the model by dipping then special dry aggregate is applied to the wet slurry coating, either by hand or by using a "fluidised bed".
The coated pattern is then left to dry when another layer of wet and dry material is applied. This is repeated, using coarser aggregate on the outer layers, until the shell is thick enough. Once the mould is sufficiently thick, the moulds are placed in a kiln for burnout, where moulds are rapidly heated to between 1000 and 1250 degrees F, and held at that temperature until all wax residues have disappeared. The place where the wax was, is now a void- hence the "lost wax" term for this process. Burnout complete, and then the pouring can proceed.

A complex and meticulous process, lost wax casting includes the following steps:

1.A sculpture is created out of clay or plaster (or directly modelled in wax).
2.A flexible rubber mould with a rigid jacket is made of the sculpture.
3.The clay/plaster is removed from this mould and it is cleaned out thoroughly.
4.The mould is assembled and a wax impression taken from it.
5.The wax pattern is removed from the mould and the artist cleans up the seams and any casting imperfections.
6.Wax sprues and vents are attached to the sculpture so that the bronze can eventually be poured into the piece and gases can escape.
7.The piece is "invested" by making a mold of plaster mixed with grog around the wax.
8.The investment meld is placed in a burnout oven to melt the wax out and dry the meld.
9.Bronze, which is an alloy consisting mostly of copper with small amounts of zinc, tin and lead, is melted in a crucible to a temperature of approximately 2000 degrees and poured into the warmed investment meld.
10.After cooling, the investment mold is broken off and the sprues and vents, which are now bronze, are removed and chased.
11.The piece is sandblasted to clean the surface of the bronze from scaling and acids and oils.
12.A patina is applied to the surface. This is a chemical process that is etched into the surface of the bronze.
13.The finished bronze is now lightly waxed to preserve its patina.