Silicone Rubber Mold

How a silicone rubber "glove" mold is made.

A glove mold is composed of two parts: a thin skin of rubber, which is the casting surface, and a plaster shell, or "mother mold", which supports the rubber liner.

In use, the rubber picks up fine detail, forgives undercuts, and allows for clean casting of many materials. The plaster shell holds the rubber rigidly in place, so the overall form is maintained. This system also uses a minimum of rubber, which is costly. 

Such molds are used for casting a variety of materials- plaster, cement, urethane resins, wax (for lost-wax casting of metal or glass) and even food products. 

This technique is commonly used in sculpture casting. I learned the process from Neil Fryzer, who had wide experience working in sculpture casting shops and at the Museum of Natural History. 

This project was for Steuben Glass. The factory needed an expendable reproduction of this cut glass pitcher, to use as a model for the glassblowers and cutters to follow. 

Here is the process:

The piece is set upside-down on a base plate. 

The piece is wrapped to protect it.

A thin blanket of clay is modeled around the piece. 

         

  

Thin metal shims are installed to create the seam line in the plaster.

 A plaster shell is laid up. 

The plaster shell is opened, cleaned up, and prepared. 

Clay is removed from the model

      

The shell is reassembled. Rubber is weighed, mixed and poured in. This fills the void created by the absence of the clay. 

After the rubber has set, the two plaster shells are separated. The rubber mold cut as needed and removed.

      

Rubber mold is ready to receive plaster.

The original and the plaster copy.

      

To expand, click images below:

Click the images below to enlarge