Rock Molds are durable, flexible, re-usable and well-detailed. They present the scenery modeler with value and versatility. Use Lightweight Hydrocal to cast small boulders, rock outcroppings, top rocks for fields and creeks, or entire rock faces. Plaster castings release easily and completely and can be attached with Foam Tack Glue or Scenic Glue. Color with Earth Colors Liquid Pigments.