Objects such as cardboard boxes, styrofoam ice chests, plastic containers and terra cotta containers make acceptable ready-made hypertufa molds. Alternatively, use wood, polystyrene or styrofoam to make your own homemade molds.
To make your own homemade hypertufa mold, butt the edges of four pieces of polystyrene foam, hold the edges together with nails, and then wrap duct tape around the outside for stability. Line your hypertufa mold with a plastic bag to keep the mixture from sticking.
Use two large cardboard boxes, one slightly smaller than the other, as a hypertufa mold to create a large planter or trough. Place the smaller box inside the larger box, and then use cinder blocks to support the outside of the larger box before adding the hypertufa mixture. Use sand, potting soil or additional cinder blocks to support the inside of the smaller box.
Many household objects make acceptable hypertufa molds, including plastic garden planters and soccer balls. To make a spherical hypertufa object, cut a soccer ball in half and fill each half with the hypertufa mixture. When it is cured enough to remove, join the halves back together with additional mixture.
Use a hole in the ground as a hypertufa mold for stepping stones or small rocks. For a smooth look, line the hole with plastic before adding the mixture.