The lost wax process of producing bronze sculpture dates back over 4000 years. In the lost wax process of bronze casting, multiple coats of rubber are applied to the artist's original, usually made of clay, to make a mold. The mold is a perfect negative of the original work. Melted wax is poured into the mold and swirled around making a thin impression of the sculpture. The mold is then separated leaving a positive wax model of the sculpture. The artist touches up this wax blank or dresses it, adding additional detail, removing seam lines and bubbles in the wax' surface. Spues and vents of wax are attached to the wax model to allow for the smooth flow of the molten bronze and to allow gases to escape. This wax positive of the original is covered with a slurry of silica flour, distilled water and an adhesive agent, covered by layers of silica sand. The first layer being a fine sand to pick up all of the detail. The following dips are gradually getting coarser sand, creating a strong shell. The shell is then heated to melt out the inner wax (thus the lost wax process), leaving a hard, heat resistant mold with all the detail of the original into which the hot bronze is poured.