The Making Of A Bronze
I like to inform people as often as possible about the complex process of creating a bronze as most people seem to be totally unaware of what goes in to it. I find too that once clients are informed they have a much deeper awareness of and appreciation for their investment.
Most bronzes are cast using the classic “Lost Wax” method which has been used for centuries.
1. Most of my sculpting is done using a plasticised modelling clay which does not dry out. Sometimes I’ll use wax or even plaster depending on the effect I’m looking for but I find the plastillene to be the easiest to work with. Once I’m sufficiently inspired to create a piece I’ll generally find plenty of reference pictures to assist with form and proportion. An armature is first created to support the clay and this could be made of wire, steel bar or even polyurethane foam that has been carved into the basic shape first. The actual sculpting stage could take as little as one day to 3 months depending on how challenging it is and the ‘creative flow’ as I call it. Once I’m happy with the finished piece I’ll sign it.
2. On completion I’ll deliver the clay piece to the foundry where they will create a sillicone rubber mold. If it is a large or complex piece different sections are moulded separately. Once this is done fibreglass ‘shells’ are made to preserve the integrity of the rubber molds shape and to prevent distortion when pouring the wax.
3. The next stage is to make a wax ‘positive’ and this is done by pouring several thin layers of a special molten wax into the mold. The mold is turned to ensure the wax reaches into every detail and is then poured out. Small pieces are sometimes cast in solid bronze but generally they are hollow and so the wax is built up to 4 or 5 mm thick. The wax positive is then removed from the mold and wax ‘sprues’ are attached at critical points and these will become the channels that the bronze will flow through to reach all areas during the casting process. They also function to eliminate trapped air and bubbles which are one of a myriad things that can affect the casting process.
4. During this process the wax positives will be worked on to restore any imperfections and return them to near perfect renditions of the original artwork.
5. The sprued wax casting is dipped in a liquid ceramic material called slurry and then coated with a very fine sand that ensures the finest details are retained, often including the artists finger prints. This process is repeated several times, with at least two coats of the finest sand as the first layers, to capture all the surface detail. Coarser sand is used for the final layers. After each coating of ceramic the piece is hung up to dry, thereby gradually increasing the layers and thickness of ceramic. The ceramic pieces are bound tightly with wire,. This is crucial to increase their integrity and prevent them from blowing apart during the bronze pour.
6. Once thoroughly dry, the piece is put in a kiln and the wax is melted out of the ceramic leaving an empty shell. ( This is where the term Lost Wax Process comes from)
7. The ceramic shells are then heated while the bronze is being melted and brought up to the exact temperature for pouring. The white-hot bronze is poured into the heated ceramic mold. Pouring temperature ranges from 2000 to about 2600 degrees Fahrenheit.
8. When the bronze is cool, the ceramic shell (investment) is broken away, revealing the bronze. The piece is sandblasted to remove every speck of ceramic The sprues and pour spout are ground off and any mold marks or other blemishes polished away. If there are multiple pieces then these will be welded together and all of the original detail will be restored by cutting, filing, chasing, chiselling and grinding. Every stage requires highly skilled workmanship and attention to detail.
9. At this point we have a completely restored bronze version of the original clay artwork. The raw bronze color is similar to ‘Fools Gold’. We are now ready to apply the patina which is made up of the acids and chemicals used to create different coloring effects to finish off the bronze. The bronze is heated and by using a delicate balance of heat and chemicals which are sprayed or brushed on the patina is applied and built up until it's the desired color. The high spots of the sculpture are often rubbed with Scotchbrite pads to keep the high spots light and to add depth and modelling to the finished bronze.
10.Molten clear wax is then applied and rubbed down to seal the piece and it is now ready to be mounted on its base which could be anything from various woods to marble, granite or even resin blocks.
People often wonder why bronze is so expensive but as you can see, apart from the talent of the artist who creates the original work, the process of casting is highly labour intensive and materially expensive.It also requires tremendous skill and experience at every stage of the process which can take anything from 2 months to a year to complete depending on the size and complexity of the piece.
So when gazing at a beautiful bronze in its chosen space, it is the result of years of inspiration, failure, experience, frustration, self expression and well honed skills by multiple people who have all invested something of themselves into a ‘bronze’ that will likely become an heirloom and a timeless testament of creative energy