What is the edition size?

Unless stated otherwise, each bronze sculpture will have an edition of 30. The terracotta pieces are one-of-a-kind unless a mold is made.

How is a bronze made from a clay sculpture?

This is a complex process called "Lost Wax Casting" that involves over 30 individual steps completed at a fine arts foundry by skilled artisans. The simplest summary of the process is that we go from a positive original sculpture to a negative rubber mold, to a positive wax, to a negative ceramic shell investment mold, to a positive bronze casting.

First, the artist provides the foundry with the original sculpture. This work can be created using a variety of materials, although clay is the most common. The sculpture is then turned over to a professional mold maker who will create a flexible "negative" rubber mold of the work, faithfully capturing the smallest details of the original. This flexible mold is cradled by a rigid plaster "mother" mold to provide support. This is the first "positive to negative" step.

The rubber and plaster mold is then turned over to the foundry where it is used to create a wax copy of the original clay sculpture. This is first "negative to positive" step. Molten wax is poured into the mold and allowed to cool. The wax is a specially formulated micro-crystalline petroleum based wax made specifically for this purpose. The wax may be poured into the mold and "slushed" around the inside surface to create an even thickness of approximately 1/4 inch. Alternatively, depending on the piece, the wax may be brushed into the mold to control and create the surface. The usual technique to acquire the proper thickness is between 2-3 coats of wax at cooler temperatures for each subsequent coat. The hottest wax, 250 F, is the most liquid and is used in the first coat to ensure the wax has picked up all the detail of the mold.

After the wax has cooled in the mold, the mold sections are separated and the wax copy of the original clay sculpture is removed. When this wax is removed from the mold, there are usually small imperfections in the surface. These imperfections, as well as the seam line where the mold had been separated, must be removed. This process is known as "wax chasing" and is accomplished by skilled and experienced artisans. Often the sculptor will participate in the process as well to ensure that the surface and form are true to the original.

At this point, a series of sprues and gates are created in the wax copy which will allow the metal to flow in and the gases to flow out when the bronze is poured. This process consists of creating a pour cup, down sprue, gates and vents, all made of wax. A good foundry will design a minimal sprue system that decreases the number of gates which touch the surface of the sculpture. This helps ensure the integrity of the form and the artist's sculptural intent.

The next step involves creating a ceramic "investment" mold around the wax copy and sprue system. The process involves dipping the gated wax sculpture in a colloidal slurry and then coating the slurry with fine silica sand. The first two coats use a very fine grit sand to imprint the detail of the sculpture, with subsequent coats using increasingly coarse grit sand. The number of coats needed for a particular casting is determined by the size of the sculpture and the need for additional strength in the pour process. This application process typically requires a minimum of 6 coats for small pieces with the largest castings requiring up to 20 coats. This can take between 4 days and 2 weeks.

Next comes the burnout process. This is the "lost wax" part of the casting. The ceramic shell mold, with the wax sculpture and wax gating system inside, are placed into a large burnout kiln which is preheated to 1450 F. The wax must be melted out quickly to keep any expansion to a minimum. Expansion in the wax will cause cracks to form in the ceramic shell. At the same time the wax is melted out, the colloidal slurry coating and the silica sand are "fusing" together to form a hard and strong ceramic negative into which the molten bronze will be poured. This is the second "positive to negative" step.

After the ceramic shell is burned out and allowed to cool, it is loaded into a different kiln called a preheat kiln. This kiln is then preheated to 1500 F for several hours. Bronze is melted in a blast furnace and once it reaches the correct temperature of 2100F, molten bronze is poured into the ceramic shell, utilizing the sprue and gating system previously created. This is the final "negative to positive" step.

Once the bronze, which has been poured in the ceramic shell investment mold, has cooled, the ceramic shell is broken off using large pneumatic hammers or hand held air chisels. After the majority of the shell is removed, the casting is sand blasted to remove the final pieces of ceramic material.

After the shell is removed, is is necessary to cut off the gating system from the sculpture. This is done with a large abrasive wheel mounted on a steel table and by carbon rods. Once the "rough" casting is ready, is is given to another highly skilled artisan called a "metal chaser" for the final surface finish. This process involves the use of electric and pneumatic power tools in a variety of shapes and with many types of abrasives to weld, grind, and sand the rough bronze into finished form.

The last step in the actual production of the sculpture is the patina. This process uses a combination of various acids and heat to control the oxidation of the bronze and achieve the desired result. The three main acids used are very weak solutions of ferric nitrate, cupric nitrate, and liver of sulfur. These acids give us various shades of brown, green, and black.. The various tonal qualities and shades of color are achieved by varying the strength of the chemical, the temperature of the bronze, and the technique of the application.

The final bronze sculpture is then attached to a base and the process is completed.