The Process | Casting & Metal
There are many parts to the foundry process and casting in metal. It is referred to as investment casting or the lost wax method of bronze casting. We followed the artist through the mold and watched the foundry create wax and a ceramic shell. Watching a bronze pour is fascinating, and many foundries do offer this in their tours. In this process pages, we continue with following Bridgette through her process of bronze casting.
Pouring the Bronze Alloy
The bronze alloy used in many modern foundries is made mostly of copper with trace amounts of silicon and other elements. The bronze alloy itself comes in the form of ingots or bricks.
This bronze alloy can be heated in a furnace to various temperatures but never lower than 1900°F when preparing to be poured. Once molten, the foundry carefully pours the bronze from a crucible into the heated ceramic shell. When the bronze has cooled, the ceramic shell is "devested" or removed to expose the bronze cast.
(Another image of this process with a different sculpture. This is again a photograph from Deep in the Heart Art Foundry in Bastrop, Texas.)
Welding and Finishing
Once the foundry pours the different parts of the sculpture, they are welded together. The metal is "chased" by grinding down the unwanted metal and sandblasted and buffed to remove any lines and imperfections. Once the metal chasing process is complete the artist is invited back to inspect the bronze sculpture. She uses the photographs of the original clay sculpture to make sure that the bronze is an accurate reproduction.
A patina is the color of a bronze. The foundry applies various chemicals while heating up the metal. Three water soluble chemicals form the basis for most patinas: Ferric Nitrate produces reds and browns, Cupric Nitrate creates the greens and blues and Sulphurate Potash produces black.
Bronze patination is an art form in itself. Ms. Mongeon often watches and gives artistic direction in the patination process. Once completed the bronze sculpture is ready for delivery and installation.
Bridgette must make sure that everything is ready to receive the sculpture. Now it is on to delivery, installation and dedication.