Sculpt design from clay.

Make the Mold

1. Roll oil-based modeling clay to 1/4-inch thickness on a work surface. Draw desired patterns on paper and place them on the clay. Cut around each pattern with a knife. Place clay pieces on an uncut copy of a stepping-stone-size paper pattern (about 12 x 12 inches), which has been glued to a plywood work board. Sculpt a design model by shaping and joining clay pieces. Spritz with nonstick cooking spray.

 

Apply latex.

2. Brush a thin layer of mold latex over the surface of the clay model. Apply slowly to prevent air bubbles. Dry overnight and repeat the process until the mold reaches 1/4-inch thickness (20 to 25 coats for reusable molds). When thoroughly dry, remove mold from the clay model and boil for 10 minutes to strengthen the latex.

 

Frame finished mold.

3. Make a shallow square box to hold the rubber mold. For the box frame, use 1 x 3-inch pine furring strips cut to the size of the mold, and secure strips with screws. Use a square of Masonite for the bottom of the box. Insert rubber mold, design side up, in box.