Lost wax casting

Each figure is special in its own way and requires 14 work steps.

An artist creates an original artwork from wax, clay, or another material. Wax and oil-based clay are often preferred because these materials retain their softness. Bosse himself cuts his models in brass.
Mold making
A mold is made of the original sculpture. Most molds are at least two pieces, and a shim with keys is placed between the two halves during construction so that the mold can be put back together accurately. Most molds of small sculptures are made from plaster, but can also be made of fiberglass or other materials.

To preserve the fine details on the original artwork’s surface, there is usually an inner mold made of latex, vinyl, or silicone which is supported by the plaster part of the mold. Usually, the original artwork is destroyed during the making and initial deconstruction of the plaster mold.

This is because the originals are solid, and do not easily bend as the plaster mold is removed. Often long, thin pieces are cut off of the original and molded separately.

Sometimes many molds are needed to recreate the original sculpture, especially large ones. (If only one cast will be made and the sculpture is made of wax or another low-melting-point material, this step may be skipped.

Once the plaster-and-latex or rubber mold is finished, molten wax is shot into it with a wax injector.
Removal of wax
This wax copy of the artwork is removed from the mold. The artist may reuse the mold to make more wax copies. Normally the rubber molds live for several years.
Each wax copy is then “chased”: a heated metal tool is used to rub out the marks that show the “parting line” or “flashing” where the pieces of the mold came together. The wax is “dressed” to hide any imperfections. The wax now looks like the finished bronze.
The wax copy is “sprued” with a treelike structure of wax that will eventually provide paths for molten brass to flow and air to escape.
The carefully built wax trees are surrounded by a steel flask. The flask with the tree in it is filled up with heat-resistent investment powder mixed with water. About one hour later the investment is ready for the burn-out cycle.
The burn out oven is heated about 725 degrees. The wax melts and runs out. The melted wax can be recovered and reused, although often it is simply burned up. Now all that remains of the original artwork is the negative space, formerly occupied by the wax, inside the hardened investment mold.
The temperature of the steel flasks is reduced to about 600 degrees. The needed quantity of brass is melt by electricity in a crucible.
The casting temperature of the fluid brass has reached about 1.000 degrees and is now poured in vacuum into the investment molds.
The investment is hammered or sand-blasted away, releasing the rough brass. The spruing, which are also faithfully recreated in metal, are cut off, to be reused in another casting.
Just as the wax copies were “chased,” the bronze copies are worked until the telltale signs of casting are removed, and the sculptures again look like the original artwork. Pits left by air bubbles in the molten brass are filled, and the stubs of spruing filed down and polished. All models are marked with Bosse/Austria.
The bronze is colored to the artist’s preference, using chemicals applied to heated or cooled metal. Using heat is probably the most predictable method, and allows the artist to have the most control over the process. This coloring is called patina.
After being black patinated the items are high-polished on certain places so to have its typical charme as Bosse created a long time ago.