How to built/construct a hollow rock replica from fiberglass materials?
You want to Buy a.) fiberglass cloth (fiberglass mat might work if its a big, simple rock) b.) polyester resin OR A.) Fiberglass cloth (or mat) B.) Epoxy Resin You can get polyester resin and fiberglass at a most bigger hardware stores. Epoxy resin you will have to find at a boat building supplies store or online. They make some eco-friendly epoxies that are used in zoos to make fake rocks and stuff. Link below. Call these guys up, they will help you with what you need. Polyester is much cheaper, but is also pretty nasty to use (a respirator is strongly suggested). The same cloth/mat can be used for both. If you want this rock to be complete (so it has a bottom as well as a top) then you might want to use the fiberglass to cover a Styrofoam core. Otherwise, use a real rock (preferably a smooth one) to make a mold. Cover it with mold release, apply the glass and resin, pop the rock out, and there you have it. Then use the mold release again in the mold itself, and apply more fiberglass
