From Christopher Wagner: Casting the First Sculpture

By Christopher B. Wagner

This past week Paul and I finished working with our first model in the “Between Here and There” project. Despite having the modeling finished, I still needed a lot of work to have a completed sculpture. During the modeling session I used plasticine clay, which is an oil based clay that can’t be fired, but it also won’t dry out. This makes it ideal for sculpting because there is no need to continuously wet it or even to cover it at the end of each session—but in order to create a finished piece I must make a mold of it. Afterwards I can cast the sculpture in a number of different archival materials.

In preparation for making a mold I went over the sculpture, plotting seam lines, figuring out how many parts the mold will be broken down into, and whether or not it will need to be cut apart. I also need to decide how many molds to make. For this first piece in the series I had to cut off the model’s left arm and create a separate mold for it in order to remove undercuts which I couldn’t work around. I was able to do the main body of the sculpture with a three-part mold.

For this project I used a rubber and fiberglass mold. The first layer, which is painted on, is a two-part silicone rubber which is very flexible and can capture pristine details. Multiple layers of the rubber are necessary to give the required strength for multiple castings. The rubber alone isn’t enough for making a mold though; it needs a rigid “mother mold,” which keeps the rubber in the right place for casting. This can be a variety of rigid casting materials but I used a fiberglass. With an assembled mold I cast a copy of the sculpture into polyurethane.

Many hours are required to finalize the piece. This includes cleaning up seam lines, reassembling the sculpture, filling it with a rigid material to add strength to the polyurethane (in this case I used expanding foam), and finally painting it. The initial casting is referred to as an artist proof and basically serves as a prototype for the sculpture edition. As of right now I am still experimenting with finishes, deciding how I will finalize the piece’s surface. For me the final decision regarding a finish is the most tedious element of the entire process. I will certainly be obsessing about it for the next few days if not weeks.

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