The foundry notes below are excerpts from my book "The Building of Courage"

Some five thousand years ago during the Akkadian period, an artist carved an image in beeswax covered it in liquid clay and placed it in a hot fire. The wax melted out or “lost”, leaving an empty space. Bronze - tin and copper - were melted together and was poured into the empty space of the clay. When the metal cooled, the artist knocked the clay shell from the metal. The first bronze was cast in the “Lost Wax” process.

Ancient “Lost Wax” bronze castings have withstood the centuries, and elements of the “Lost Wax” process have been refined over the centuries. Yet today, bronze casting in foundries is essentially the same as it was in 2,000 BC.

The finished clay model of "Courage" is cut into multiple sections

Step one is to saw apart the clay and wire sculpture, cutting into as few pieces as possible. “Courage” was cut into three pieces, each separate piece having its own mold made. The parts created by the molds will be welded back together and each weld painstakingly cleaned up to replace the detail lost by the mold making. I am not a part of this step. I drop off the finished clay and leave before the foundry makes their cuts. After spending all of those days building, I can’t bear to watch the cutting.

Mold making

The original clay pieces are painted evenly with a liquid rubber (angelate), the same material as a dentist uses to make your dentures. When completed, the mold is opened and the original clay is removed. The rubber mold is made of half of the sculpture at a time. Notice the raised registration dots on the edges of the mold. This is to help align the two halves and keeping the mold in perfect alignment. “Courage” has taken on the look of a saint with the crown of dots and flanges around her head.

The original clay sculpture is undamaged and will be used as reference in the chasing steps to keep the wax and metal castings true to the original.

Creating the wax replica

When the rubber cures, a rock hard protective mold made of re-inforced plaster is built around the rubber. The mother mold halves are then put back together for the wax pouring. On “Courage” the face area in the mold was first painted with a thin coat of wax to pick up all of the fine detail of the face. Then the mold was put together ready for the wax pour.

Wax is melted, poured into the mold and evenly “slushed” inside. Slushing is repeated three times using cooler wax each time to avoid melting the previous coat. The wax wall will be about 3/16” thick —- any more or less might create flow problems for the bronze.

When the mold is opened and the rubber peeled away, an almost perfect wax reproduction is removed, then checked against the original clay.

The wax pieces are chased then applied to a tree

“Wax chasing” is the process of joining the wax pieces, removing seams and repairing imperfections with by skilled craftsmen using heated customized soldering irons and dental tools.

I visited the foundry at this point to check the work and integrity of the wax pieces. I had two sculptures made and in checking, I found that one gave me goose bumps when I saw her but the other one did not. Carefully I looked at the face of the second one and found that it was not quite right. The mouth was “off”. It was lacking the curled smile that I realized was my daughter’s smile. This was the first time I was aware I had added her smile.

The foundry repoured the entire wax piece since we knew the mold was right. When I held the new wax, I again got goose bumps ... the smile was right.

“Vents” (thin wax sticks) and “gates” (thicker wax sticks) are affixed to the wax reproduction forming the “tree”. In the casting process, the space occupied by gates become runways through which the metal flows and trapped gas escape.

Ceramic Shell

The next step or “Investment” is the process of building a hard shell around the wax sculpture. When the wax has been melted out, the investment will serve as a mold for the hot bronze.

The building of the ceramic shell begins by dipping the gated wax or tree into vats of slurry followed by sand. This process builds a very thin wall of silica around the wax. The process is repeated once daily for approximately two weeks, or until a hard shell about ½” thick forms around the wax.

The phrase “lost wax casting” comes from the wax being melted or “lost” from the ceramic shell. The shells are “de-waxed” in a high pressure autoclave; plaster invested shells are still de-waxed in a kiln.

Pouring the Bronze

This is the “Show” of the making of a bronze. Here I am going to revert to technical verbage from several sources on the internet since I can’t think of an easy way to give you the info. Here goes.

A graphite crucible, is filled with bronze ingots that are melted. The metal begins to melt at 1700°F. Bronze stops flowing when confronted with cold, which might occur if molten bronze was poured into a room temperature shell; so at the same time the bronze is being melted in a furnace, the ceramic shell is heated in a kiln to approximately 1100°F (see the photo on the right of the glowing shells).

When the “Dance of the Pour” begins, the crucible is lifted out of the furnace. At the same time, the glowing ceramic shells are brought out of the kiln to the pour area. Two artisans operate the crucible in a “jacket.” The artisan with the controls is the “lead pour,” the artisan maintaining the crucible balance is known as the “deadman.” A third member of the pour team the "safety"pushes away dross and slag on the surface of the molten bronze.

The entire pour is very fast and very precise; one crucible of bronze holds 140 lbs and can fill one or two medium shells or ten or more small shells. The first pieces poured are those with thin walls and intricate details; requiring hot, fluid bronze to move throughout the channel system. Silicon added to the bronze helps the “flowability” of the bronze instead of using lead or tin. A modern day addition to the centuries old process.

Removing the ceramic shell

Removing the shell from the metal is called “Devesting”. When the piece is cool enough to handle, hammers and power chisels and a lot of skill are used to knock the investment off the solidified metal. The gates and sprues are removed with a high intensity electric arc that can cut through the bronze like butter.

Welding, chasing and sandblasting

After the three sections of courage are welded back together, the bronze must be chased to take down weld line formed by the joining of two planes and to fill in the slight imperfections.

The chasing starts with large electric or pneumatic grinders to remove the bulk of the unwanted metal. Then, more refined and smaller tools such as die and pencil grinders are used to re-create the surface texture.
Before going to the patina area, the casting is sandblasted to remove any fine investments from the bronze. Notice in the photo above the tin color of the finished sandblasted bronze next to the original clay pieces.

Here is where I come back to the foundry and check the metal against the clay to make sure it is correct. With these two sculptures I had done, one of them was leaning forward a bit too much, so she went back to the metal area to be cut apart above the ankles and re-welded to stand more upright.

Patina, final finishing and assembly to base

This is the anxious part for the artist. The patina is the enhancement of bronze by spraying chemicals on the hot bronze for the color. There are three water soluble compounds that form the basis for most patinas and I used two of them for “Courage”. I originally wanted a light tan sculpture instead of my usual “Classic” colored pieces. The foundry cast the hand and cloth piece for me and tried a white/tan patina for me to look at before the whole sculpture was cast. I didn’t like it, and they did another patina test. It was not the right colors for “Courage”. The colors were too light and ethereal looking and “Courage” needed to be strong and grounded, a warrior with presence. So back to the “Classic” bronze color. Ferric Nitrate was applied first to produce the classic reds and browns. Notice in the photos that a blow torch is used to heat up the metal and the chemicals are sprayed on and set with the flame. I want the color of the piece to have a depth of colors so the chemicals are applied then rubbed off a bit then more applied and so on until the colors are right. I wanted the piece to look a bit aged so a slight dusting of Cupric Nitrate was added to create the greens.

Take a close look at the last photo on the right. The patina work is finished and now it is time to apply the hot wax to seal the colors. Here the green color which was applied last disappears into the browns when hit with the hot wax. Magic and the patina artist knowing what the end result will be, irregardless of what it looks like before the end.

After putting the thin coat of clear wax over the bronze to enhance and preserve the patina “Courage” was screwed into the granite base and her journey came to an end.