Building Lightweight Rocks
Robert Miracle shares how he crafted his faux rocks. After a bit of trial and error, he found the perfect mixture of natural materials to create his lightweight boulders and stones. He created a mixture comprised of 20 percent sand, 20 percent mortar, 10 percent fire clay and 50 percent paper to produce a realistic rocklike finish.
Robert suggests practicing the mortaring technique on small forms until you get used to working with mortar and cement. Robert found many of his materials, such as buff-colored mortar, iron oxide pigment and fire clay, at a cement company. The fire clay makes the mixture sticky and easier to work with, says Robert.
Robert made the rock forms out of a few simple items: cement blocks, rebar, 14-guage-wire fencing and chicken wire. He bent rebar over the cement blocks and covered it with wire fencing. Then he added a layer of chicken wire. He spread the mortar over the chicken wire, leaving areas that would be touched by water bare to prevent the uncured mortar from absorbing water.
Once the "rock" was covered with mortar, he used different colors of iron oxide pigment to add accent colors to the rock. He used a 4-inch paintbrush to work the iron oxide into the mixture to create the different earth tones. After completing a rock, he covered it with plastic and burlap to keep the moisture in and to prevent the finish from cracking. He let each rock cure for 24 hours.