Fake rocks can be used in a variety of scenarios, including train tables, science projects, movie sets, and themed events or parties. While real rocks may be easy to find, they are also heavy, dirty, potentially dangerous, and can be difficult to dispose of when in large quantities. Fake rocks, on the other hand, can be made fairly inexpensively and offer a great afternoon craft project.
Break apart pieces of Styrofoam to serve as the bulk of your rocks. If you're using sheets of Styrofoam, stack them together to make them bigger. Do not worry about the shape, as rocks come in all shapes and sizes.
Spray some spray foam onto a sheet of wax paper to create additional rocks with a flat bottom surface--perfect for making a fake rock wall.
Cover your Styrofoam rocks with self-adhesive plastic or fiberglass mesh so that the grout has a surface to adhere to.
Use a stirring stick to mix enough grout to cover your fake rocks. Slather the grout on the outside of the rocks with a putty knife. Be sure to follow the manufacturer's instructions for tinting your grout.
Inspect the outer surface of your fake landscape rocks after they are dry. Fill in any unsightly cracks or pits.