How to Make Lightweight Stepping Stones

Choose a design and form. Use deep pie pans or rectangular baking tins or build forms to your desired size and shape. Use wood, nailed or screwed together at corners, with a plywood bottom. Bend thin sheet metal, aluminum or even heavy garden vinyl edging into squares, rectangles or irregular shapes and set on plywood or sturdy plastic. Make rigid foam board insulation into forms by cutting with a utility knife and taping pieces together, set on plastic or foam board.

Pick a light concrete material, which can weigh from 35 to 100 pounds per cubic foot, a fraction of regular concrete. Pumice and scoria, volcanic glass found in the western United States, are popular; so are vermiculite and perlite, made by heating certain types of rocks. Foam concrete uses tiny balls of expanded polystyrene and is called "eps concrete" or "epscrete." All these lightweight concretes are as durable as regular concrete but generally lack the compressive strength of natural rock concrete.

Coat the insides of your forms with mineral oil or similar substance to prevent concrete from sticking to the forms. Do not use no-stick cooking sprays, which are not strong enough. Place the forms where they can dry without being exposed to blowing dust or other foreign objects. Set them level so one side of the stone will be smooth and level. (If you want both sides smooth, build a wood box with plywood or rigid plastic top and bottom, but open on one side to pour in concrete.)

Mix concrete with water according to the directions, using a garden trowel or similar tool, in a tub, wheelbarrow or similar container. Pour it into the forms with a bucket or spread it in the forms with a mason's trowel. Fill the form to the height desired, usually to the top of the pan or container. Smooth the surface with a trowel after the concrete starts to set.

Add any decorations, like bits of stone, handprints or carvings, after concrete has started to firm but before it has hardened. Make sun faces or similar images by building those molds into the bottom of the form, or placing plastic or metal shapes in the bottom of the form. Be sure to coat these molds with oil.

Let concrete dry, at least overnight, preferably two to three days. Set the stones in place in a patio or walkway, but do not use them for at least a week, to allow the concrete to cure completely and avoid the possibility of cracks.