The "Lost Wax Process".
| This description of the Lost Wax process has been extremely simplified and does not begin to address the many in between stages, complications, variations, and the exhausting endurance of hours, days, and months that elapse in the process of creating a single bronze. |
Step 1: Original sculpture.
I use clay to create the original sculpture. Depending on size, sculptures can be cast as a single piece or cut into pieces.2. Creating the Molds and Wax.
A rubber mold is made directly onto the original sculpture. A plaster "mother mold" is made encasing the rubber. Molds are removed, reassembled, and filled with melted wax. The hardened wax is removed and carefully hand-finished to replicate the original. I generally rework the wax and sign each piece at this point.
3. Spruing the Wax
Wax rods are attached to the sculpture (called gates and sprues) in a manner resembling road maps all leading to the cup or funnel which is attached at one end of the wax rod.
4. Investing the Wax
Hardened wax is first dipped into a liquid "shell" vat. While still wet, it is slowly lowered into a dry silica sand, forming a rigid shell. This process occurs over and over (generally a two week period) to build up the shell, giving it strength. The other form of investment – is actually called investment casting and it is done in one step, the wax is carefully lowered into a cylinder of liquid plaster which then solidifies around the wax.
5. Burning Out the Wax
The wax, with its heavy shell coating, is heated in a kiln, which dries and bakes the shell and melts out all of the wax. This process leaves only a hollow shell or cylinder, and is origination of the term "lost wax" or cire perdue(Fr).
6. Pouring the Bronze
The bronze ingots are melted (2100 degree F) in a crucible which is sitting in a special furnace. The cylinders or Ceramic shells are buried in a san pit to hold them upright, and protect everyone from bronze, should the cylinders or ceramic shell give way when bronze is poured into the hollow cavity of the cylinder. Melted bronze is then poured into the hollow cavity within the shell.
7. Revealing the Bronze
Once the bronze is cool, the shell is broken away with hammer and chisel. Bars and the funnel are also removed at this time.
8. Sandblasting
Any remaining shell is removed by two stages of sand-blasting; first with coarse, then with fine sand.
Step 9. Chasing the bronze
Imperfections to the surface, as well as marks and scars left when removing the bars and funnel are repaired in a process called "chasing".
Step 10: assembling and welding
The sculpture is reassembled and welded into the correct positioning. Welded seams are again "chased" by the artist until the bronze is identical to the original work.
11. Patination
The coloration of the bronze is achieved by applying heat and chemicals to the surface of the piece. Application of a patina is actually a chemical reaction created on the surface of the piece with the use of heat. Controlling a patina is a lot like working with watercolors, in that the same ideas can be recreated but not always the same affects. Chemicals can be dipped, sprayed, or brushed on in various degrees of heat known as "applying the patina".
The process of casting is a time consuming one. These steps can represent 8-12 weeks of foundry time, and are the work of skilled craftspeople.