I find skulls and human anatomy, fascinating! I took a few bronze casting classes, where you sculpt out of wax, then place the wax in a plaster or cement structure with venting. You then melt out the wax and pour in molten bronze. After it cools, you take a hammer to the plaster and have a raw sculpture. You trim off the vents and then polish and patina and finish your sculpture. This is an ancient form of sculpting known as the lost wax method. The patina that you see on this skull is caused by natural oxidation and rapid cooling of the molten bronze. The piece is small, about the size of a softball, but weighs 17 pounds, as bronze is super dense!