DIY Foam Rocks

Polystyrene foam is a good source of material for DIY rocks.

Rocks made from polystyrene foam are good artificial substitutes for the real thing. They are used in science fair projects, plays, and landscaping. DIY foam rocks can be made from polystyrene foam that is purchased from hardware stores. Leftover pieces from packing materials or pillows can also be used. The materials must be cut and shaped to the desired dimension, and wrapped in mesh tape that is coated with a solution. This procedure is used in order to strengthen and protect the artificial rocks. The rocks may be painted for further protection, and to add more realism to their appearance.

Things You'll Need

• Extruded polystyrene foam
• Utility knife or scissors
• Concrete mix
• Water
• Mesh tape
• Glue
• Spatula or putty knife
• Brown Earth tone or gray paint
• Paintbrush

Instructions

1. Determine the size of the rocks you wish to make. Take the utility knife and cut the foam into several pieces. If necessary, glue parts together to form layers.

2. Shape the foam. Trim off the excess parts, and gouge holes in it in order to simulate craters.

3. Wrap the mesh around each piece. If the mesh is not self-adhesive, secure it with glue. Cut away the excess tape.

4. Stir the concrete mix and water together. Use a spatula or putty knife to coat the rocks with the solution, and then let the rocks dry before proceeding.

5. Apply at least one more coat of the solution to the rocks. When they are dry enough, paint them either gray or brown.

Tips & Warnings

• Substitute clay, dry powder paste, or plaster of Paris for the concrete mix.

• Spray foam may be used instead of solid foam.

References

• “Lionel FasTrack Model Railroads: The Easy Way to Build a Realistic Lionel Layout”; Robert Schleicher; 2009
• Fake Rock University: How to Make Rocks
• GlassTropics: Making Artificial Rocks

Resources

• Concrete Vogue; How to Make Fake Rock; May 2010
• Polytech Foam Products Inc: How to Create Faux Rocks with Foam