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Lost Wax Method of Making Sculpture

How Most Bronzes are Made

Lost Wax Methods of Sculpture

If you are interested in collecting sculpture, you may wonder about the processes that are used in creating this three dimensional works of art.

The methods used vary by artist’s preference and sculpture medium.

Madonna, Jesus and St. John The Baptist

The traditional method for creating bronze sculptures is known as lost wax.

This method can be used to create both original sculptures and reproductions. The term “lost wax” refers to the wax that is used to create negative space in a mold.

Here is an overview of how the process works.

The Original Sculpture

If the piece is to be a brand new work of art, the artist creates a life-size original piece in wax, clay or another soft material.

Although soft materials are preferred, it is possible to create rubber molds from original sculptures of any number of materials. This is necessary when creating a reproduction of an older work.

Mold Making

The mold is generally made of a plaster, fiberglass or other hard shell lined with latex, silicone or another soft material that will pick up the fine details of the original sculpture.

Molds are generally made in at least two pieces for small sculptures, and many pieces for larger artwork. A shim with keys is usually placed between mold pieces to make them easier to accurately reassemble.

Waxing

When the mold is complete, it is carefully removed from the original sculpture and reassembled.

Hot melted wax is poured inside and manipulated to cover all parts of the mold.

Three or more coats of wax are generally applied in order to achieve a perfectly even coat of the desired thickness (usually 1/8 inch but sometimes more for a larger piece).

Chasing

The hollow wax impression is carefully removed from the mold.

In a process called chasing, a hot metal tool is used to remove imperfections and hide seams. The wax piece should be fully finished during this step.

Gating

Sometimes called “spruing,” this is a complicated process in which wax rods are attached in a network to the finished wax piece. These rods form the path that the molten bronze will take when poured, as well as pathways for air to escape.

Slurry

A hard outer coating called a ceramic shell is created by dipping the wax piece into liquid silica and then into a dry silica stucco.

The mixture is then allowed to dry fully. Several applications may be necessary to achieve the desired thickness.

Burnout and Testing

After the slurry has dried into a hard shell, the piece is heated in a kiln.

This finishes the hardening process of the ceramic shell and melts the wax figure.

The wax is poured out, leaving behind an empty space inside the shell. The shell is then tested for thickness and flow using plain water and patches are created as necessary.

Pouring

The shell is reheated in the kiln to approximately 1500 degrees.

Meanwhile, the bronze is heated in a furnace to approximately 2000 degrees. The bronze is then poured into the shell and allowed to cool.

The shell is removed via sandblaster and/or hammer.

Metal Chasing

The gating tubes, which have been reproduced in bronze, are cut off, then the entire piece is chased just as the earlier wax model was.

Grinding, sanding and other techniques are used to ensure that the sculpture is perfect.

Patina

Many artists choose to apply a chemical coating to their bronze statues to change the color. On reproductions, this color is chosen to represent the natural aged look of the original statue.

Some new pieces are similarly treated, although artists may choose virtually any color.

Artists can also add color to the sculpted piece either in the casting process by adding alloys to the metal or after casting by painting, etching or other processes.

Lost wax methods can be used for both new and reproduction sculptures.

Although the process is time consuming, it will yield a beautiful bronze statue that will last for many years to come.

The finished product relies almost exclusively on the skills of the creator, however, so if you are having a reproduction made it is important to carefully select your reproduction artist.

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