How to Make Molds Out of a Stone Sculpture

Molds, which are impressions of existing objects, are used to cast designs in new materials. They can be one part, which is for a flat-backed design, two part, which is for a three-dimensional design, or three part, which is for a hollow design. Molds can be made for almost anything. You can make a mold of a model, a sculpture, or an existing object like a toy or prop. You can even make a mold for models or sculptures made from many different types of materials, including stone.

Instructions

1. Take your stone sculpture and coat it with mold release. This will protect the sculpture from the molding material and allow you to remove the mold more easily from the sculpture.

2. Roll a piece of modeling clay into a long, thick tube and wrap it around the sculpture, dividing the sculpture into 2 equal sides. Press the tube against the sculpture, shaping it into a thin "wall."

3. Make a small plaster mixture by adding water to gypsum powder in a bucket. Mix until you have a soupy consistency.

4. Paint the plaster all over 1 side of the sculpture, filling in all the small details and cracks. This is an impression coat, and will provide the base for the rest of the mold.

5. Let the impression coat dry for a few hours, or until you can touch it. Make another mixture of plaster.

6. Paint the plaster onto the same side of the sculpture, over the impression coat. Press strips of burlap into the plaster, letting the plaster soak into the burlap.

7. Let this coat of plaster dry. Apply a second coat over the burlap strips and let it dry.

8. Layer coats of plaster and burlap over the stone sculpture, until you have a mold half that is several layers thick. Repeat Steps 3 through 8 on the opposite side of the stone sculpture.

9. Let the entire sculpture cure for a full day. Once it has cured, gently ease the plaster away from the stone sculpture by separating the mold halves at the clay wall.

10. Clean the clay out of the mold with a toothbrush and a little water. If you like, you can sand the inside of the mold to get smoother casts.

11. Fit the plaster mold pieces back together, lining up the edges. Wrap a rope around the outside of the pieces to secure them.

12. Carve a hole into the bottom of the mold, using a craft knife to scrape away the plaster. This hole will be used for pouring when you decide to cast.